Concrete, wall, and drainage answers for homeowners

Much of a concrete or drainage job happens below and beside the part you will see. Excavation depth, hauling away old slabs and soil, base stone, forming, reinforcement, drain pipe, and cleanup all take labor and trucking before anyone finishes a surface. A quote that looks lower may simply leave some of that out.

Site conditions move the number more than most owners expect. Slow-draining glacial till and wet clay call for more thought about base and water than free-draining ground does. A steep lot, a narrow side yard that keeps machines out, a long wheelbarrow haul, or a back yard that needs a pump truck each change the method. Finishes such as exposed aggregate or stamping, and curved or shaped edges, add finishing labor.

Honest quotes diverge for reasons you can check. One may assume the existing base is fine while another assumes it must be dug out, and one may price a thicker slab or a stronger mix for heavier vehicles. Neither is wrong, but the comparison only works once each quote states its assumptions, so compare scope first and totals second.

Start with scope in measurements. A quote for “a driveway” cannot be compared with one that lists the length, width, and area to be removed and poured. Washington’s Attorney General advises getting written bids that detail the scope of work, the materials, and the total price, so ask any bidder who gives a single lump sum to break it out.

Then go down the same list for each bid. Removal: who breaks up, loads, and disposes of old concrete or soil. Base: material, compacted depth, and what happens to soft spots. Thickness and mix: guidance from the American Concrete Institute ties slab thickness to expected traffic, concrete strength, and how stiff the soil is, so a driveway used by delivery trucks or an RV is a different product from a walkway. Reinforcement and joints: what is used and where joints will be cut. Drainage: where water goes. Restoration: lawn, irrigation, and edges. Permits: who applies and who pays.

Last, check the paperwork. L&I says a registered contractor must put the registration number on bids, so look for it and verify it before comparing anything else. Ask which lines are allowances, because an allowance is an estimate that can move after work starts.

Cracks alone do not decide it. The National Ready Mixed Concrete Association notes that most random early-age cracks look bad but rarely affect structural integrity or service life, while closely spaced pattern cracking and freeze-thaw damage can lead to real deterioration. A stable hairline crack may only need sealing. A crack that is widening, stepped, or paired with a sunken edge points to the base or to water.

An overlay is a new layer bonded to the old slab, so it depends on what is underneath. Pavement engineering guidance on bonded overlays says the existing slab should be structurally sound with good support, serious distress must be repaired first, and bond quality usually decides success or failure. A surface that is flaking, hollow-sounding, or moving will carry its problems into the new layer.

Replacement usually means more work up front but it resets the base. If the slab sits on soft or wet soil, drains toward the house, or has been lifted by roots or frost, fixing only the surface repeats the failure. A useful test is to ask what caused the damage and what will change underneath so it does not return. If the answer is only about the surface, you are buying a repair, whatever it is called.

Rain in western Washington falls mostly from fall into spring, with December and January the wettest months and July and August the driest, according to the Western Regional Climate Center. Dry-season weeks are the most sought after, so asking for quotes in the wetter months, before you need the work, gives you room to compare bids and choose a start date.

Concrete can be placed in wet or cool weather, but it takes planning. Rain on fresh concrete can mix into the surface, so crews cover the work and remove standing water, and rain-damaged surfaces sometimes need grinding or removal. Cold works differently: industry guidance defines cold weather as an average daily temperature below 40 degrees F for more than three consecutive days, and says fresh concrete must be protected from freezing until it reaches about 500 psi, roughly two days after placement. Local winters are mild, but nights near or below freezing still happen. The winter pouring page covers that in more detail.

Ground conditions are the quieter factor. Saturated soil makes excavation messy, slows base compaction, and can hold up drainage work. A firm date months ahead with no weather language is a guess, so ask how a rain day or frost is handled and who decides.

Think in stages, because each has its own disruption. Demolition and excavation are the loudest, with breakers, loaders, and haul trucks. Base work and forming follow, and the crew needs room for stone deliveries and equipment. The pour is often finished in a single working day for a modest area, with a concrete truck occupying the street or driveway for part of it. Walls and drains add digging, backfill, and sometimes inspections between steps, which can stretch the timeline.

Curing sets the pace afterward. Ready-mix industry guidance calls for keeping concrete moist and protected for at least three days after placement, and parking-area guidance from the American Concrete Institute keeps cars off for three days and trucks for seven unless strength tests show about 3,000 psi. Cold weather slows strength gain, so the same driveway may need longer in winter.

Plan for access limits. Cars may have to park on the street, the garage may be unreachable, and deliveries, trash pickup, and sprinkler schedules may need rerouting. Pets and children need a clear boundary around fresh concrete. A realistic schedule from the contractor lists the days the surface will be unusable, not just the day of the pour.

Access comes first. Measure gate and side-yard widths, note overhead branches and wires, and mark where a concrete truck or excavator could stand. A narrow path can turn a machine job into a hand job, which changes the method and the quote.

Next, what is under and around the work. Washington law requires a utility locate before digging, but public locates do not mark private lines, so note sprinkler zones and valves, septic components, buried power to a shed, landscape lighting, pool lines, and any drains you know about. Find your property corners or any survey you have, and mention neighbors’ fences or trees close to the line. Collect HOA covenants and any architectural approval forms.

Finally, document water. Take photos after heavy rain showing puddles, wet crawl spaces, overflowing gutters, and where downspouts discharge, and describe when problems started and any past repairs. Photos of cracks, settlement, and slab edges help a contractor judge repair against replacement, and a rough sketch with measurements lets every bidder quote the same job.

A slab is only as good as what it sits on. Ready-mix industry guidance on cracking lists topsoil, soft spots, and poorly compacted fill as sources of uneven support, and recommends removing topsoil and soft spots, compacting the subgrade, and keeping it level and sloped for drainage. The American Concrete Institute’s parking-area guidance adds that soil type, moisture, and density should be uniform, and that non-uniform areas should be replaced with material similar to the rest.

Western Washington adds its own twist. Glacial till and clay hold water, wet winters keep soil soft, and fill from past grading can hide poor material. Where the slab sits next to a building, the residential code calls for the lot to be graded so the surface falls at least 6 inches within the first 10 feet from foundation walls, and where barriers prevent that, drains or swales plus hard surfaces sloped at least 2 percent away from the building.

Base work is buried once the concrete is placed, so you cannot inspect it later. Ask what stone, what depth, and what compaction method are planned, and ask to see the compacted base and forms before the truck arrives.

Washington requires construction contractors to register with the Department of Labor and Industries (L&I) before they advertise, bid, or work. L&I’s Verify tool shows whether the registration is active, whether workers’ compensation is in good standing, any violations, and whether lawsuits have been filed against the bond. Registered contractors must put their registration number on advertising, bids, and business communications, so a missing number is a question to ask right away.

A suspended registration means a requirement such as the bond or insurance is no longer met, so check status on the day you sign and not only when you first shortlist someone. Confirm that the business name on the contract matches the registered business and that the owner names match what Verify shows. Some trades, such as electrical and plumbing, also require separate state licensing or certification, and the same tool shows that.

What registration does not prove: workmanship, experience with your kind of site, a clean record with past customers, or that the bond is large enough for your project. Treat it as the floor. After it, look at finished jobs, call references, and read reviews with some skepticism.

Under RCW 18.27.040, the surety bond is $30,000 for a general contractor and $15,000 for a specialty contractor, raised for registrations on or after July 1, 2024. A contractor may use an assigned savings account instead. Liability insurance is a separate requirement, and L&I’s registration page lists the coverage it accepts.

The bond is not insurance for you. It backs the contractor’s obligations to workers, taxes owed to the state, suppliers, and judgments for breach of contract, including improper work. Anyone with a covered claim can sue the contractor and the bond. If claims exceed the bond, they are paid in a set order: employee wages first, then breach-of-contract claims by a party to the construction contract, then subcontractors and suppliers. A homeowner suing for breach of contract has two years from substantial completion or abandonment.

Because one bond serves every customer, worker, and supplier of that contractor, a large remodel can outrun it. L&I also runs a Homeowner Recovery Fund for owner-occupied homes of up to four units: after a final court judgment against a registered contractor (ordered after July 1, 2026), you apply within 90 days of the case ending, and payments of up to $25,000 depend on available funds. The eligibility rules are recent and narrow, so confirm them on L&I’s page before relying on the fund.

RCW 18.27.114 requires a contractor who agrees to repair, alter, or build on residential property of four or fewer units, for a price of $1,000 or more, to give the customer a “Notice to Customer” disclosure statement before starting work. It identifies the contractor’s registration and bond, warns that the bond may not cover your claim and is not for your exclusive use, says your property may be liened if suppliers, workers, or subcontractors go unpaid, says you may withhold a percentage of the contract as retainage, and says you may ask for original lien releases. The contractor keeps your signed copy for at least three years, failing to comply is an infraction, and a contractor must prove the statement was given to bring a lien claim.

The statute does not write the contract for you, so the agreement is where protection comes from. Washington’s Attorney General lists what to include: the work, total price with taxes and fees, materials, start and completion dates, payment schedule, sign-off procedures, cleanup, how changes are handled, and any written promises about the work after completion.

Add details that prevent arguments: measurements, thickness, base, and drainage described in the scope, who applies for permits and pays for inspections, what removal and restoration include, and what happens if hidden conditions appear. Read every page before signing and keep a complete copy.

The contract sets the deposit and the payment schedule, so negotiate them before signing. Washington’s Attorney General advises keeping the initial down payment small and holding back final payment until you are satisfied with the finished work and know subcontractors and suppliers have been paid. A schedule tied to milestones, such as base complete, concrete placed, and final cleanup, keeps your payments close to the work actually done. Be wary of any request for most of the price before work begins.

Retainage is a built-in option. The disclosure statement under RCW 18.27.114 tells you that you may withhold a contractually defined percentage of the contract price for a period of time. That option only becomes real if the contract says how much is held, until what date, and what condition releases it.

Concrete and drainage work often meets surprises: soft soil, buried debris, a root mass, a drain line in an unexpected place. A change order is a written, signed amendment that states what changed, the effect on price, and the effect on schedule. Without one, there is no clear record of what you agreed to pay for. Agree that extra work does not start until the order is signed, except for a genuine safety problem.

Under Washington’s lien law (chapter 60.04 RCW), people who provide labor, materials, or equipment to improve your property can record a claim against it if they go unpaid, even when you paid your contractor in full. That is why the disclosure statement warns that your property may be liened. Law-firm guides to the statute describe a claim as generally due within 90 days after the last work, followed by a lawsuit within eight months of recording, so a lien notice deserves a prompt response: tell your contractor and consider speaking to an attorney.

The word “notice” covers two different things. A subcontractor or supplier you did not hire directly usually has to send a written notice of the right to claim a lien. On an occupied single-family home, RCW 60.04.031 limits that lien to the amount you have not yet paid the prime contractor when the notice reaches you. Separately, on projects over $5,000 the prime contractor must post a notice at the job site, and a posted building permit with the required information satisfies it.

A lien release is a signed statement that a person has been paid and gives up the claim. Ask for releases with each payment and at the end. This is general information and not legal advice, and lien deadlines are strict.

Washington requires construction contractors to register, and L&I says working without registration carries substantial penalties and fines. L&I can issue civil infractions, refer cases for criminal prosecution, or both. For the contractor, a practical consequence is payment: RCW 18.27.080 bars a contractor from suing to collect pay for work that requires registration unless they held a valid registration when they contracted, with limited room for substantial compliance.

For you, the exposure is different. Unregistered contractors are usually working without a bond, so a damaged property or an abandoned job may leave you with a claim against someone who has little to collect. The Homeowner Recovery Fund covers work by registered contractors only. A bid from an unregistered business leaves out those protections, so it is not comparable to a registered bid.

Permits are another pressure point. Under WAC 296-200A-110, a city or county issuing a building permit must verify the registration of the contractor applying for it, which is one reason an unregistered contractor may ask you to apply for the permit in your own name. If that request comes up, treat it as a reason to verify and ask why.

The Federal Trade Commission’s Cooling-Off Rule lets you cancel certain sales made at your home, workplace, or a temporary seller location until midnight of the third business day after the sale. The seller must tell you about the right, give you two copies of a cancellation form, and give you a dated contract or receipt explaining it. The rule also applies when you invited the salesperson to your home. Saturdays count as business days. Sundays and federal holidays do not.

Exceptions matter for contractors. The FTC lists purchases needed to meet an emergency and sales that result from your own request that a seller visit your home for repair or maintenance, though anything beyond that request is still covered. Sales made after negotiating at the seller’s permanent place of business are also outside the rule. Washington’s Attorney General points to RCW 63.14.154 as a state cancellation right for retail installment contracts solicited in person away from the seller’s business address, so financed work may have an extra layer.

To cancel, sign and date one cancellation form and mail it, or send a letter if no form was given, postmarked by the deadline. Use certified mail with a return receipt and keep a copy. If you are unsure whether a contract is covered, treat the deadline as real and ask the Attorney General’s office or an attorney right away.

L&I’s guidance separates two problems. If a contractor is unregistered or you suspect fraud, L&I has an online way to report illegal contracting. If a registered contractor left the job unfinished or the work does not match the contract, the main remedy is a civil claim. L&I describes suing the contractor and the bonding company in the superior court of the county where the work was done. L&I forwards the papers to the bond company and the contractor, but you must also serve the contractor yourself, and L&I does not give legal advice or track your case.

Before filing, L&I’s fact sheet suggests giving the contractor a written list of problems with a deadline to respond, and considering mediation. If your contract included a written notice about the Construction Defect Claims Law (chapter 64.50 RCW), you must follow its steps before suing. A homeowner has two years after the work was substantially completed or abandoned. Include the contractor’s registration number and the bond number from Verify in your filing.

If you win a judgment against a registered contractor and cannot collect, the Homeowner Recovery Fund may help. Damage to people or property may also fall under the contractor’s liability insurance, which you claim from the insurer directly. Keep the contract, photos, messages, and payment records. This is general information, not legal advice.

L&I’s warnings about door-to-door paving crews describe a pattern: uninvited visits, claims of leftover material from another job at a bargain, demands for cash, unregistered status, and final bills well above the original quote. L&I advises finding contractors yourself, comparing written bids, and hiring only registered contractors. L&I also warns about contractors who take a deposit and then do partial work or disappear, and without a bond behind them you have little recourse.

The paperwork shows more. Watch for no registration number on the bid, no written scope, a bare lump sum, reluctance to put promises in the contract, or reluctance to provide the disclosure statement required for residential jobs. A statement that the permit is not needed, or a request that you apply for it in your own name, deserves a direct question. The answer should be about the work, not about avoiding the registration check cities must run.

Sales pressure is the third category: a price good only today, no time to read the contract overnight, or a refusal to give references. A sound contractor can give you time. If you do sign at home and regret it, the federal Cooling-Off Rule may give three business days, but treat that as a backstop and not a plan.

The statewide baseline is the Washington State Residential Code, built on the International Residential Code. The 2021 edition took effect March 15, 2024, and a newer edition has been proposed for 2027. Its list of work exempt from a building permit names “sidewalks and driveways” and does not name patios or stairs, so those are decided city by city, especially when they attach to the house or serve an exit door. An exemption never authorizes work that violates the code or other local laws.

Cities then add layers that a building-permit exemption does not cancel. Tukwila’s exemption sheet, for example, notes that public works permits are still required for impervious surface even where the building permit is exempt. Work in the public right-of-way, such as a driveway apron or curb cut, is typically permitted separately. Zoning can add setbacks and limits on lot coverage or impervious area. Some adopted stormwater codes begin at 2,000 square feet of new plus replaced hard surface.

Critical areas and shorelines are the other overlay. Washington’s Growth Management Act requires cities and counties to protect wetlands, aquifer recharge areas, frequently flooded areas, geologically hazardous areas such as steep slopes, and fish and wildlife habitat, and each writes its own rules. Shoreline jurisdiction generally reaches 200 feet landward of regulated waters, and exempt work must still follow the local shoreline program. Retaining walls have their own thresholds, covered in the retaining walls section below.

Responsibility starts with city code. Federal Way’s code requires abutting owners to keep sidewalks fit and safe for public travel, and puts the burden of repair on the owner or occupant who damages one, including by planting trees or other vegetation. Tacoma’s sidewalk page cites chapter 35.69 RCW together with its own code as placing sidewalk repair on the private owner, even where a previous owner caused the damage.

Responsibility and permission are separate. Even when the owner pays, the sidewalk is in the public right-of-way, so the city controls how it is rebuilt. Federal Way says owner-performed work at a single-family property needs a right-of-way permit and bond, plus insurance and compliance with city standards, and says the city may do needed work itself and assess the cost against the property as a lien. Tacoma says a permit is needed to reconstruct sidewalks in the right-of-way and that its code calls for a Washington licensed and bonded contractor.

Details differ elsewhere, and so do rules for tree roots: Federal Way’s page notes a homeowners association may sometimes hold that duty. Before you hire anyone, find out whether the city has flagged your sidewalk, which permit applies, and who in public works issues it. Ask a contractor whether the quote includes the right-of-way permit, the bond, and traffic control.

Under WAC 296-200A-110, a city or county issuing a building permit must verify the registration of the general or specialty contractor applying for it. In practice the contractor of record applies, and Bellevue’s page says the city prints the contractor’s registration number on the permit. Some cities also let an owner apply for work on their own home, but then you, not a registered contractor, answer to the inspector. Put in the contract who applies, who pays the fees, and who schedules inspections.

Consequences for skipping a required permit vary by city. Kent’s fee schedule lists an investigation fee for work started before a required building permit. Olympia’s code requires a special investigation before any permit for such work, with an additional punitive fee on top of the permit fee. Pierce County’s guidance for unpermitted residential buildings describes applying after the fact with drawings and an engineer’s report, or removing the work. None of that applies to work that is truly exempt. The risk is work that needed a permit and did not get one.

It matters most at sale. Washington sellers complete a disclosure statement under RCW 64.06 based on their actual knowledge of the property, and buyers’ inspectors and lenders may find missing permits. Keep permit paperwork, receipts, and photos of drains and base work before they are buried.

A city permit and an HOA approval are separate. Covenants recorded against your lot, plus the association’s rules and architectural review process, can govern materials, locations, and drainage, and procedures range from very detailed to very general, according to a Washington Secretary of State workshop handout. Associations may charge fines after notice and a chance to be heard, and any aggrieved party can sue, so written approval before the work is the safer course.

Property lines are the second limit. Fences, hedges, and old walls are often built near the true line rather than on it, and an online parcel map is a planning tool, not a boundary survey. Marking a boundary is normally the work of a professional land surveyor licensed by the state. If a retaining wall, footing, or drain will sit close to the line, a survey avoids encroaching on a neighbor, which can mean tearing work out.

Working near a neighbor’s land also has practical limits. Grade changes can send water onto their side, and excavation can undermine soil that supports their fence or structure. A wall near the line may fall under stricter local setback rules, since Edmonds, for example, limits walls in setback areas to 3 feet above original grade. Talk to the neighbor first, and keep the utility locate, survey stakes, and photos of existing conditions.

Washington’s Underground Utility Damage Prevention Act, chapter 19.122 RCW, requires an excavator to notify the one-number locator service before digging. The Utilities and Transportation Commission (UTC) describes the notice as two to ten full business days before the work is scheduled to begin, not counting weekends and legal holidays, and says a locate is required even to install a sign. Excavators outline the dig area in white before calling. Since January 1, 2026, excavators may not begin until every facility operator in the area has responded.

The duty falls on whoever excavates. A homeowner digging fence post holes must call, and a contractor doing the work should call and give you the ticket number. UTC notes a narrow exemption for owners or occupants of noncommercial property digging fewer than 12 inches, but footings, drains, trenches, and base excavation usually go deeper. Penalties exist for digging without a locate, and the excavator can be liable for damage and repair costs.

Marks show the approximate location of public utility lines and last up to 45 days. Private lines are not marked by public utilities, including irrigation, septic components, power to an outbuilding, landscape lighting, and pool lines, so a private locator is the usual way to find them. Within two feet of a mark, UTC advises only small hand tools, because some lines lack protective casings.

The 4 and 5 inch figures come from the Illinois Ready Mixed Concrete Association’s residential guidance, an industry source rather than a code. The American Concrete Institute’s guide to concrete parking lots explains why no single number fits every driveway: thickness comes from the traffic loads, the support the soil provides, and the concrete properties, and the guide notes that driveways sometimes have to carry relatively heavy loads. A driveway that takes a loaded delivery truck, a motorhome, or a dump truck is a different design problem from one that parks two cars.

The base matters because concrete spreads load over a wide area, so the failure to avoid is uneven support, not weak support. The American Concrete Pavement Association says that above all other design concerns, uniformity is of utmost importance, and it warns against a base that holds water under the slab. The Illinois guidance calls for removing unstable material, placing a compacted crushed-stone base at least 4 inches thick, and never pouring on frozen ground.

In western Washington, slow-draining soils, fill on sloped lots, and wet winters all raise the stakes under the slab. A site with a spring, a fill pad, or a steep grade may need a geotechnical engineer’s opinion before anyone settles on a thickness.

The Portland Cement Association’s position is that cracks in a slab on ground are controlled mainly by uniform support under the slab and by joint spacing tied to slab thickness. Welded wire fabric holds random cracks tight once they form and does not stop them from forming. If it is placed at least 2 inches below the surface, a designer can use it to allow longer joint spacing.

Placement decides whether it works. Engineering guidance that cites the Wire Reinforcement Institute puts wire and bars in the upper part of the slab, within the upper third of its thickness, and says welded wire should never be laid on the ground and pulled up after the concrete is placed. Reinforcement stays mostly inactive until the concrete cracks, then limits how wide the crack opens. Bars or wire running straight through a contraction joint can keep the joint from opening, so designers limit or cut them there.

Plastic fibers, typically dosed around 0.1 percent by volume, reduce plastic shrinkage cracking, the fine cracks that form in the first hours. The Association says they should not be expected to replace wire mesh in a slab on ground, and they do not change joint spacing.

Concrete shrinks as it dries while the ground holds the slab back, so tension builds until something gives. Joints give it a place to give. For a 4 inch slab the 24 to 36 times rule works out to about 8 to 12 feet between joints, and the Illinois Ready Mixed Concrete Association lists 8 by 8 to 10 by 10 foot panels. Panels should be close to square, with length no more than about 1.5 times width, and the groove should be at least one quarter of the slab thickness deep.

Timing counts as much as layout. Conventional saw cuts are generally made 4 to 12 hours after finishing: cut too late and the slab may crack on its own, cut too early and the edges ravel. Isolation joints run the full depth of the slab and belong where it meets a house, a garage slab, steps, or a pole, so each part can move on its own.

Other causes of random cracks include a poor base, water added at the truck, finishing over bleed water, and little or no curing. A hairline crack outside a joint is a normal outcome, not proof of bad work. Cracks that open, step, or spread are a different matter, and the cracks section below explains how to tell.

The Illinois Ready Mixed Concrete Association lists foot traffic after 48 hours, vehicles after 7 days, and heavy loads after 28 days. Redmond’s sidewalk guidance is more cautious: it asks for 7 days before walking, 10 days when temperatures are below 60 degrees, 7 days before passenger cars (when the concrete reaches roughly 70 percent of its strength), and 28 days for heavy loads. Both follow the same pattern of light use early and heavy use late.

Concrete keeps gaining strength well beyond those dates. The American Cement Association says most strength develops in the first few weeks, that strength is usually measured at 28 days, and that concrete continues to harden after that. The National Ready Mixed Concrete Association adds that cooler temperatures slow strength gain, which matters for a Pacific Northwest fall or spring pour.

Edges and corners are the weakest parts of a young slab, so even a car should stay off an edge early. Heavy means concrete trucks, dump trucks, delivery trucks, moving vans, and loaded trailers. A cold-weather pour may call for longer waits, and the winter pouring page covers that case.

Pavement research separates two designs. In one, the new concrete is made to stick to the old surface so the two act as one slab. In the other, it sits on a separating layer and acts as its own slab. Iowa State University’s guide to concrete overlays of asphalt parking lots says the first approach suits an old surface in low to medium distress that is relatively uniform and stable, and the second suits high-severity distress, provided the base underneath is stable. If the distress is excessively severe, it says, the pavement may not be a good candidate.

The same guide says a wet, spongy, or moving base must be stabilized before paving, and it names poor drainage under the pavement as a major cause of distress that has to be repaired first. Its thinnest option, a 2 inch layer, is allowed only under tight conditions: cars only, enough existing asphalt remaining, fiber reinforcement, and small joint panels. Those are parking-lot rules, not a driveway recipe, so an engineer’s design is the right basis for a residential job.

Raising a driveway also raises the grade. It can leave a lip at the garage door, climb a sill or siding, or turn water toward the house. Removal adds demolition and hauling to the job, but it exposes the base so the cause of the damage can be found and fixed.

The Illinois Ready Mixed Concrete Association recommends a minimum slope of 1/4 inch in each foot, about 2 percent, to promote positive drainage. That matches the model International Residential Code, which requires paved surfaces within 10 feet of a foundation to slope at least 2 percent away from the building. Washington’s adopted version also requires the ground beside a foundation to fall at least 6 inches in the first 10 feet. A building department can confirm what applies on a given lot.

Where the water goes matters as much as the slope. In Currens v. Sleek (1999), the Washington Supreme Court restated that surface water may not be artificially collected and discharged onto adjoining land, and that a landowner who changes drainage must act with due care to avoid unnecessary damage to others. Cities and counties add their own rules for curb cuts, the street edge, and stormwater, and work at the edge of the public right-of-way may be subject to local requirements.

Slow-draining ground in much of western Washington means water aimed at a lawn can sit there. If a driveway slopes toward a garage door or a basement wall, the fix is to change the grade or add a drain, not to rely on the slab alone.

Slabs sink when the ground under them loses support: soil washed out by water, poorly compacted fill or utility trench backfill, or soft soil. A Missouri Department of Transportation technical brief on highway pavements describes slab stabilization as pressure insertion of a highly flowable material under a slab to restore lost support, and states that it is not used to raise a slab significantly. Polyurethane foam is now the primary material there. The brief reports that cement grout has been phased out because of erosion potential, that over-injection can crack slabs, and that service-life estimates ran from roughly 5 to 15 years depending on the source. Those are highway findings, so treat them as a caution, not a residential promise.

The honest limit is that lifting restores support but does not remove the reason support was lost. If water keeps washing soil out, or the slab is already broken into pieces, replacement with a rebuilt base is often the sounder route.

Tree roots lift slabs by growing and thickening beneath them. Extension guidance says grinding a raised edge reduces the trip hazard but does not stop the lifting, that root barriers and a root-excluding base are long-term options, and that cutting roots larger than roughly 2 to 4 inches in diameter can harm or destabilize the tree. An arborist should weigh in before any large root is cut.

Failures tend to trace back to a short list. The American Concrete Pavement Association describes pumping, where water, heavy loads, and fine soil combine to wash support out from under a slab, and it calls uniform support the central goal. The National Ready Mixed Concrete Association ties surface scaling to too little entrained air, low strength, poor finishing, poor curing, and heavy de-icer use on new concrete. Extra water added at the truck, missing joints, and little curing lead to random cracks.

Loads and roots come next. A slab sized for cars cracks and settles under repeated delivery or dump trucks, and the American Concrete Institute notes that driveways sometimes have to take relatively heavy loads. Tree roots lift and crack slabs, and a large tree beside a driveway is a long-term risk.

Care slows the damage. Keeping water from running under the slab, clearing moss, avoiding de-icers, and watching small cracks for movement all help, while a failed base is usually a replacement question. Compare replacement bids on what happens below the slab, not only on the surface finish.

A decorative concrete trade article on slip resistance ranks broom finishes highest among smooth finishes, followed by sandblasted and then troweled surfaces. It adds that stamped or imprinted surfaces can be more slip resistant than smooth ones, depending on the number and spacing of texture channels, and that too much texture becomes a trip hazard. Exposed aggregate is rougher than a trowel finish, but test results for it are hard to find, so ask to walk on a wet sample.

Sealers change the picture. The same article says film-forming sealers can encapsulate the surface and reduce its natural traction. One stampable overlay maker says sealed surfaces can become slippery when wet and requires slip-resistant additives, while a data sheet for a penetrating silane sealer reported the same pendulum slip number on broomed concrete before and after treatment.

In western Washington the bigger traction problem is often what grows on the finish rather than the finish itself. Moss and algae on a shaded, damp patio make any surface slick (see the cleaning answer in the care section), and deeply textured surfaces are harder to clean. A finish that suits a sunny, dry patio can be a poor match for a tree-shaded one.

The trade association for concrete pavers says a damaged paver can be replaced without disturbing its neighbors, that repairs to stamped concrete are typically noticeable, and that stamped concrete can crack from settling or freeze-thaw. Those points are plausible, and they come from a group that favors pavers. Stamped concrete behaves like any slab: joints control where cracks form but cannot prevent them, and a patch rarely matches the original pattern and color.

Pavers have their own failure modes. University extension installation guidance calls for a compacted base of about 4 to 6 inches plus an inch of bedding sand, more base over soft clay, and edge restraint, since pavers without it move and separate. Moss grows in shaded, damp joints, and joint sand needs occasional topping up. Where the base was poorly compacted, pavers settle into dips, and fixing that means lifting them and rebuilding the base.

Stamped concrete has maintenance too. The American Society of Concrete Contractors’ Decorative Concrete Council advises resealing when water repellency or color depth fades, not on a fixed schedule, because frequent resealing can build up a film that is hard to remove. Budget, appearance, and tolerance for upkeep usually decide this, and neither material is permanent.

Water that runs toward a house soaks the soil beside the foundation, feeds moisture into crawl spaces and basements, and freezes and thaws against the slab edge. The model International Residential Code requires paved surfaces within 10 feet of a foundation to slope at least 2 percent away from it. Washington’s adopted version also requires the ground near a foundation to fall at least 6 inches in the first 10 feet. A fall of 2 percent is about 1/4 inch in every foot, or about 1 inch in 4 feet, which is also the figure in extension guidance for paver patios.

Slope is easy to get wrong because a long, shallow patio can look flat while still holding a puddle. A level held on the formed base before the pour, and a hose test on the hardened slab, show low spots while the contractor can still discuss them. Corners and edges next to the house are where ponding does the most harm.

Where a wall, a property line, or a slope prevents 6 inches of fall in 10 feet, the code allows drains or swales to carry water away instead. Patio drainage and house drainage work together, so a slab that slopes away still needs somewhere for the water to go, which is the subject of the drainage work page.

Washington currently enforces the 2021 International Residential Code with state amendments, effective March 15, 2024, and local jurisdictions enforce it. The State Building Code Council has proposed a 2024 edition with a start date in 2027, so check which edition applies when you apply. Risers can be no taller than 7 3/4 inches and treads no shallower than 10 inches. Within a flight, the tallest riser may not exceed the shortest by more than 3/8 inch, and the same limit applies to treads, which is why one odd step is a trip hazard. Landings must be as wide as the stair and at least 36 inches in the direction of travel.

Handrails are required on at least one side of a flight with four or more risers, at a height of 34 to 38 inches. Guards are required along open-sided walking surfaces that are more than 30 inches above the grade below at any point within 36 inches horizontally of the edge. Guards are generally 36 inches high, and openings must stop a 4 inch sphere, with stair-specific exceptions.

Exterior doors add their own rules: a landing is generally required at the door, with limited exceptions for one or two steps that depend on door swing. These numbers describe the model code, not a plan review. Local adoption and amendments apply, so the building department decides what governs a particular project.

Frost heave happens when water in soil freezes and expands, lifting whatever sits on it. Footing-depth rules put the bearing surface below that zone. In Washington the number is local: one southwest Washington county’s plan review sheet lists 12 inches of frost protection for footings, and the MyBuildingPermit.com tip sheets on the 2021 code say footings must not bear on frozen soil. The American Concrete Pavement Association identifies frost heave as a concern mainly in freezing climates with silty soils. Lowland western Washington freezes are milder and shorter than inland ones, but silty ground is the kind that can heave.

A step sitting on compacted gravel may simply move a little with the seasons. A landing tied to the house, or poured next to the foundation, can be pulled or pushed by that movement and crack at the connection. Backfill beside a foundation is typically less compact than undisturbed soil, so a landing poured over it can settle and open a gap at the door.

Whether a footing is required, how deep, and whether the step must be separated from the house are questions for the building department or an engineer, not a rule of thumb.

Penetrating sealers soak into the pores and mostly do not enhance color. Topical, film-forming sealers sit on the surface, deepen color, and are the most common choice for stamped concrete. Hybrids do both. The American Society of Concrete Contractors’ Decorative Concrete Council says excessive or premature application of film-formers can cause visible problems, and that resealing every year to restore gloss can build up a film that is hard to remove.

Conditions matter. The council advises letting the slab dry 12 to 24 hours after cleaning, avoiding direct sun during application because bubbles can weaken the bond, and spraying then back-rolling for even coverage on textured surfaces. For conventional mixes it cites ACI 302.1, which recommends at least 7 days of curing above 40 degrees F, and manufacturers often set their own waiting times.

Color variation is mostly a construction issue. The National Ready Mixed Concrete Association lists uneven curing, differences in finishing (more troweling darkens the surface), different water-cement ratios between loads, and poorly mixed calcium chloride as causes of discoloration, and notes that texture or pattern helps hide variation. White powder on colored concrete can be efflorescence rather than fading. No general fade rate applies to pigments, so ask the colorant maker what it states.

Washington cities apply the International Residential Code’s list of work exempt from a building permit, section R105.2. Federal Way’s page lists sidewalks and driveways, fences up to 6 feet, retaining walls up to 4 feet measured from the bottom of the footing unless supporting a surcharge, and decks of 200 square feet or less that are no more than 30 inches above grade at any point, are not attached to a dwelling, and do not serve the required exit door. It does not address concrete slab patios by name, so a ground-level patio is a question for the permit center, not an assumption.

An exemption is narrower than it sounds. Another Washington city’s exemption checklist, quoting the same code language, says an exemption does not authorize work that violates the code or other local laws. Federal Way adds that work in a critical area, such as wetlands, streams, or landslide hazard areas, and in its buffers, is not exempt, and that separate permits may still be required for exempt items.

Driveway aprons and anything crossing the sidewalk or curb sit in the public right-of-way, which usually has its own approval and standards. Zoning, setbacks, and drainage rules also differ by city, so the city pages under service areas are a starting point and the permit center has the final say.

Decorative overlays are polymer-modified cementitious mortars troweled, sprayed, or squeegeed over a prepared slab. Microtoppings are the thinnest. One Euclid Chemical data sheet gives an application thickness of 1/16 to 3/8 inch for a floor and deck topping it calls suitable for exterior use, while another manufacturer’s microtopping is limited to 1/16 to 3/16 inch and to interior use only. Stampable overlays are thicker, around 1/8 to 1/2 inch in one manufacturer’s sheet, so a pattern can be pressed in. These are product systems, and preparation, primer, sealer, and exterior suitability differ from one to the next.

At the other end are structural overlays used on pavements. Iowa State University’s guide describes concrete overlays on asphalt that are designed either to act together with the old surface or to carry loads on their own, with design software generally assuming a 3 or 4 inch minimum thickness.

An overlay changes the surface, not what is underneath. Manufacturer data sheets call for a structurally sound slab, so a resurfacing is not a repair for one that is cracked and settling.

Manufacturer sheets say the same few things. One stampable overlay sheet describes its use as resurfacing structurally sound, non-moving concrete floors and exterior hardscapes, and lists steel-wheel traffic, strong chemicals, periodic immersion, and hydrostatic pressure as unsuitable. Random cracks must be repaired or they can telegraph through, and existing joints must be carried up through the new layer, cut full depth and as wide as the joints below.

Failure paths follow from that. A slab moving from settlement, roots, or a failed base will crack the overlay above the movement. Moisture moving up through the slab is a recognized risk; a decorative concrete trade article calls vapor emission uncommon but serious. Sealers, curing compounds, oil, or paint left on the old surface give the new layer nothing to grip, and delamination, the layer lifting away, can follow.

Overlay versus replacement comes down to the problem. An overlay answers surface complaints: stains, wear, color, shallow pitting, a dated look. Replacement answers structural ones: heaving, settlement, broken corners, or drainage that sends water the wrong way. If the surface is scaling, find out why first, because the cause may be in the concrete itself and can return through a thin layer.

Manufacturer sheets set preparation in numbers. They specify a concrete surface profile, a scale from the International Concrete Repair Institute’s guideline 310.2, and the ranges differ by product: one microtopping sheet calls for profile 4 to 6, while two other overlay sheets call for 2 to 4 and 3 to 5. Saying the floor will be ground is not a complete answer: the question is ground to what profile, for which product.

Bond breakers must go: grease, oil, paint, sealers, and curing compounds. Two of the sheets say to remove them by mechanical means and prohibit detergents, soaps, and acid etching. A decorative concrete trade article quotes a manufacturer’s representative saying that only mechanical methods properly clean a substrate down to sound concrete and that the bond is only as strong as the substrate itself. Weak or flaking concrete has to come off first.

Bonding steps have timing windows. One sheet recommends an epoxy primer seeded with sand, or a scrub coat applied to a saturated-surface-dry slab before it dries. Another system allows overlaying within 24 hours of priming and calls for re-priming if the surface gets wet or dirty. Temperature limits apply too, such as 45 to 85 degrees F or 45 to 100 degrees F depending on the product, which narrows the season for exterior work in western Washington.

Manufacturers publish curing and use limits, not service lives. One stampable overlay sheet allows light foot traffic about 4 hours after placement at 70 degrees F, keeps vehicles off for at least 96 hours, and calls for a full 28 days before heavy traffic or freeze-thaw exposure. A microtopping sheet from another maker says no heavy traffic until it has cured. After that, thin layers tend to show wear first where abrasion concentrates, such as tire turning points, garage thresholds, and stair nosings.

Sealer is part of the system. The Decorative Concrete Council advises resealing when water repellency or color depth fades rather than by the calendar. Overlay sheets recommend sealing for ease of cleaning and warn that sealed surfaces may be slippery when wet. One maker states that slip-resistant additives are required to limit dry and wet slip, and asks for a job-site mock-up at least 21 days before installation to approve color, finish, and slip resistance.

In a shaded, damp yard, moss on a smooth sealed overlay becomes a slipping hazard before it becomes a cosmetic one. Ask the manufacturer what cleaning methods the product and sealer tolerate, because harsh cleaning can damage thin layers.

The National Ready Mixed Concrete Association states that all concrete has a tendency to crack and that completely crack-free concrete is not possible; the aim is to control and minimize cracking. Its crazing sheet describes a network of fine surface cracks, rarely more than 1/8 inch deep, in cells typically under 1.5 inches across. They are an appearance issue and do not affect structural integrity.

Width alone is a weak test. ACI 224R, written for reinforced structures, cites 0.016 inch as a reasonable service-level crack width in dry air, according to a position statement from the American Society of Concrete Contractors. That is an engineers’ reference point, not a pass-or-fail line for a driveway. More useful checks are whether the crack has widened over a season, whether one side is higher than the other so a toe can catch, whether it follows a joint or wanders, and whether it sits over a settled or washed-out spot. University extension guidance says small cracks that seem to be growing and make a walk dangerous can be repaired.

Water that enters a crack can freeze and widen it, and a stable hairline crack can be sealed later. Cracks in a slab that is moving, or any cracking near a foundation, call for an engineer rather than a patching product.

The National Ready Mixed Concrete Association’s curing guide says curing typically lasts 3 to 7 days and warns that concrete kept dry can lose as much as 50 percent of its potential strength compared with moist-cured concrete. Accepted methods include continuous fogging or wet burlap that stays wet, plastic sheeting at least 4 mils thick, and liquid membrane-forming curing compounds. Alternate wetting and drying is not an acceptable curing practice.

Liquid curing compounds are the most common method on concrete paving, according to the American Cement Association. They can affect what comes later, though: a stampable overlay sheet lists curing compounds among the bond breakers that must be removed, and a penetrating sealer sheet says concrete should reach about 80 percent of design strength, typically 14 to 28 days, before the sealer goes on.

Weather decides the rest. The same guide says to protect concrete from freezing until it reaches at least 500 psi, and cooler temperatures slow strength gain. For cold-season pours, the winter concrete page goes into more detail. Keep de-icing chemicals off the slab the first winter, and see the earlier answer on how long to wait before driving on it.

The National Ready Mixed Concrete Association’s scaling guide suggests a silane or siloxane-based breathable sealer applied as the manufacturer directs to a reasonably dry slab, and names late summer after a few dry days as an ideal time, so the slab is protected before winter freeze-thaw. Penetrating sealers generally leave appearance unchanged. Film-forming sealers deepen color but can cause visual problems if over-applied, according to the Decorative Concrete Council. Neither makes concrete waterproof, and one silane data sheet states that it will not stop water through unsound or cracked surfaces.

How often depends on the product, and a data sheet may give no reapplication interval at all. A state transportation department study of silane treatments on bridge decks found coatings lasted at least 6 years in the field, with roughly 30 percent no longer effective after 9 years. That is a different exposure from a household driveway, and it is evidence about decline over time, not a schedule.

Sealing cannot fix a slab poured without enough entrained air, cured poorly, or finished with water on the surface. Film-forming coatings can also be slick when wet. On new concrete, wait for the manufacturer’s minimum cure time before sealing.

The National Ready Mixed Concrete Association lists the causes of scaling: non-air-entrained concrete or too little air at the surface, low strength that lets water in, improper proportions, excessive de-icing chemicals (especially on new concrete), improper finishing, and insufficient curing. It recommends about 6 percent total air for concrete with 3/4 or 1 inch coarse aggregate. Entrained air is a network of microscopic bubbles that gives freezing water room to expand. Finishing while bleed water is on the surface leaves a high-water, weak top layer that is prone to scaling.

On de-icers, the Association’s advice is to avoid them in the first winter and use moderate amounts afterward. Another printing of the same guide adds clean sand for traction and says never to use ammonium sulfate or ammonium nitrate. Research funded by the Washington State Department of Transportation found that magnesium chloride de-icers can harm concrete strength and that plain sodium chloride penetrated reinforced concrete at the highest rate. Its authors favor low-permeability mixes and minimizing de-icer use.

Spalling, where larger pieces break away, is a related but different problem and can involve corroding steel too close to the surface or impact. Western Washington winters are milder than inland ones, but concrete that is wet and freezes on a clear night can still scale, and shade keeps it wet longer.

Moss and algae favor shade and moisture. University extension and Seattle utility guidance both describe scraping with a dull blade, scrubbing with a stiff brush, and pressure washing as effective on sidewalks and patios, and early fall is an easy time to act. Moss-killing soaps based on fatty acids or potassium salts work, but dead moss still has to be removed. Zinc and copper products are toxic to aquatic life, and iron-based products can stain concrete.

Pressure washing can etch a surface, expose aggregate, or strip sealer, so use a wide fan at low pressure, test a hidden spot, and follow the maker’s directions on sealed, stamped, or overlaid surfaces. There is no single safe pressure for every surface. Redmond’s published rules prohibit sending driveway wash water to storm drains, and other cities have their own.

Efflorescence, a white powdery deposit, needs three things together, says the Portland Cement Association: soluble salts, moisture to carry them, and evaporation that draws the solution to the surface. It is unattractive but generally harmless and often fades. Dry brushing is a first step, washing in cool, damp weather adds moisture, and a deposit that keeps returning points to a moisture source to fix first. For acid cleaners and colored or sealed concrete, follow the product maker, because acid etching can weaken a surface.

The 4 feet is measured from the bottom of the footing, not from the ground you see. A wall that shows 3 feet above grade can already be over the line once the buried footing is counted. A surcharge is extra load on the soil the wall holds back: a driveway or parked vehicles above it, a building close behind it, or a slope that keeps rising. Tukwila’s handout, for example, treats a surcharge within a 45-degree angle of the bottom of the footing as enough to remove the exemption.

Cities add their own rules on top of that baseline, and some set lower thresholds. The same Tukwila handout says no wall in a critical area is exempt, and zoning can restrict walls in setbacks even when no building permit is needed. Look up your city on the service area pages and then confirm with its permit office.

Engineering is the other half. A wall near the 4 foot line, on a slope, or holding up a driveway or a house is a structural element, and the right step is a Washington-registered professional engineer, not a rule of thumb. Exempt from a permit does not mean exempt from liability if the wall fails. This is general information, not wall design.

A wall is designed around the assumption that the soil behind it drains. When the drainage fails, the wall carries the weight of wet soil plus water pressure that the design may never have counted on. Building departments list the same early signs of trouble: water accumulating behind or at the top of the wall, and water leaking through cracks or clogged weep holes.

Four weak points show up again and again. Drainage: a pipe that is crushed, a gravel zone that has silted up, or an outlet that is buried. Backfill: fine, silty soil holds water, while clean crushed rock lets it leave. Footing: too shallow, too narrow, or sitting on loose fill. Surcharge: a driveway, shed, pool, or regraded slope added above the wall after it was designed.

Western Washington makes the first one worse. Months of winter rain saturate the ground, dense glacial soil slows the water down, and a mild but real freeze-thaw cycle works on cracks. A wall can look fine for several summers and then move during its first very wet winter. A wall built without proper drainage is the one that shows it first.

Each piece does a separate job. The gravel zone gives water an easy route down. The perforated pipe at the base collects it. The filter fabric between native soil and gravel keeps fine particles from migrating in and clogging the stone. The outlet carries the water somewhere that can take it. Seattle’s published standard for rockeries shows the scale: at least 12 inches of granular drainage material between undisturbed soil and the rockery, and a perforated drain pipe at least 4 inches in diameter at the base. Other cities and engineers specify their own details.

Gravel only drains while it stays clean. A Building America guide for footing drains stresses clean washed stone because silt and sand clog the perforations, and wraps the whole gravel bed in fabric for the same reason. A pipe laid flat, or one whose end is buried in the yard, is a drain in name only.

Plan the outlet before the wall. In glacial till, the native soil is slow, so the drain may carry seepage all winter, not just storm bursts. Where that water is allowed to go is covered in the French drain section below, and it is generally not the neighbor’s yard.

Poured concrete is the usual choice where a wall is tall, narrow, or carries a driveway or building load, because it can be reinforced and engineered for those forces. It needs formwork, a sound footing, and drainage, it cannot flex, and cracks are managed rather than avoided. Repair is harder than with units that can be lifted out.

Segmental block is dry-stacked interlocking units, sometimes tied back with grid reinforcement into the soil behind. It tolerates small movement and curves well. Its performance depends heavily on the compacted base and the drained backfill, which are buried and hard to inspect afterward. Timber works for short terraces, but wood in ground contact is exposed to decay, so treatment, drainage, and eventual replacement all belong in the plan.

Rockeries are stacked large rocks without mortar. Seattle’s rockery standard says the city does not consider rockeries to be retaining walls, caps its prescriptive design at 6 feet, and requires an engineered design above that. Compare quotes by scope and engineering, not by material alone: a wall priced low by leaving out drainage or a sound footing costs more when it is rebuilt.

New York City’s Department of Buildings gives a useful checklist for owners: a wall leaning out of alignment, cracks or holes in the soil or pavement along the top, soil or pavement swelling at the bottom, severe cracks, bulging, or displaced material in the wall, water accumulating behind or at the top, and water leaking through cracks or clogged weep holes. It also notes that freeze and thaw cycles damage walls over time. White streaks or staining below joints point to water moving through the wall.

What to do: photograph the wall with a tape or level in the frame, mark the ends of cracks with the date, and recheck after each heavy rain. Move vehicles, stored material, and new landscaping loads away from the top. Send downspouts and irrigation away from the area. Do not dig at the base or the top of a wall you are worried about.

Treat three situations as urgent: movement that is increasing, a wall holding up a driveway, building, or neighbor’s land, and anything that moved during a storm. The right professional is a Washington-registered engineer, and the right call before digging near the wall is 811.

Repair makes sense when the wall is basically sound and the cause is identified: clogged weep holes, a blocked outlet, a few displaced caps or units, a hairline crack that has stopped moving. Adding drainage behind an existing wall usually means excavating behind it, which is real work and sometimes a permit item. A repair that treats the crack and leaves the water pressure in place usually fails again.

Rebuild becomes the honest answer when the lean is increasing, the wall has bulged or rotated, the footing is broken or undermined, or the original build had no drainage and silty backfill. An engineer may offer a partial rebuild or a retrofit stabilizing method, but those are engineered fixes and not a task for guesswork or a rented excavator.

There is no single service life for a retaining wall. It depends on the material, the drainage, the soil, the loads added since, and maintenance, and drainage and construction quality usually matter more than the label on the material. Ask the designer what design life the wall was built for, and ask the permit office whether replacing a wall counts as new work.

Start with where the line actually is. Fences, hedges, and old stakes are poor evidence of the boundary. A survey by a land surveyor registered in Washington settles it before a footing is poured in the wrong place.

Rules get stricter near the line. Tukwila’s handout, for one, generally does not allow walls over 4 feet in a required yard setback without a waiver, and lists a shared wall on a property line, with both owners agreeing to maintain it, as one of the cases where a waiver can be considered. Other cities handle it differently, so check the city page for your area under service areas.

Digging for a footing and drain can undermine the neighbor’s soil, and a wall that fails can damage both sides. Water is the other issue: under Washington case law, collected drainage cannot simply be discharged onto adjoining land (see the neighbor question in the drainage section). A written agreement about access, shared maintenance, and who pays for what is far easier to make before the work than after a problem. For liability questions, an attorney is the right adviser.

The residential code requires guards on open-sided walking surfaces with a drop of more than 30 inches to the floor or grade below, and says guards must be at least 36 inches high measured above the walking surface. Washington’s 2021 code carries those provisions. They matter when a patio, path, or yard edge sits above a wall, where the wall top is the open side. Whether a lawn or planting bed counts as a walking surface is something the local building official decides, so ask before assuming either way.

A solid fence adds wind load, and fence posts set into the backfill or the cap can interfere with drainage and with the wall itself. That is an engineering detail to settle before the wall is built, not after. Tukwila’s handout, for example, counts ornamental designs anchored to a wall toward its total height, and city fence-height limits vary, so the wall and the fence may be measured together.

A fence tall enough to double as a guard has to be built like one, which a privacy fence is not by default. A designer or engineer should account for any railing from the start, because retrofitting posts into a finished wall is harder than planning for them.

University of Minnesota Extension notes that people often believe they have wall leakage when the moisture is condensation: warm, humid outside air that enters the basement, for example through open windows, condenses on the cool wall and floor. The wall is cold because it is in contact with the ground.

A commonly suggested homeowner check is to tape a square of aluminum foil or plastic tightly to a bare wall, sealing every edge, and leave it for a day or two. Droplets on the room side of the foil point to condensation from indoor air. Dampness on the wall side, or a dark patch beneath the foil, points to moisture coming through the wall. It is a rough check, not a diagnosis, and it is worth repeating after a stretch of wet weather.

Other clues: water lines or damp at the base of the wall after several days of rain, damp on only the coldest surfaces such as cold-water pipes, and a hygrometer reading. EPA suggests keeping indoor humidity below 60 percent, ideally between 30 and 50 percent. In western Washington both can occur in one house, condensation in warm months and real water in a saturated winter.

Start outside. University of Minnesota Extension points to missing or poorly placed downspouts that concentrate roof runoff near the foundation, and to ground that slopes toward the house. Building Science Corporation likewise puts roof water and grading first: keep surface water from becoming ground water before spending on anything below grade.

Then groundwater. The below-grade water table can rise seasonally, and west of the Cascades the wet season stacks months of rain on slow-draining glacial soil, so the ground around a foundation can stay saturated for weeks. Saturated soil pressing on a wall and slab is hydrostatic pressure, and it pushes water through cracks, the joint where wall meets floor, and any pipe penetration.

Footing drains are the third suspect. Minnesota Extension notes that many existing houses have no subsurface drainage system, and that existing ones can fail from collapse, clogging, or broken connections to a sump. A house below a slope can also receive both surface flow and underground seepage from above, which a drain between the slope and the house can intercept. Because the causes stack, fixing the simplest upstream item first often changes what the basement needs.

The Concrete Masonry and Hardscapes Association describes efflorescence as a deposit of soluble salts, usually white, and says three conditions must combine: soluble compounds in the material, moisture to carry them to the surface, and a driving force such as evaporation or hydrostatic pressure. Remove any one and it stops. Its guidance is written for masonry, but concrete walls and slabs behave similarly.

What it tells you depends on the pattern. Light, uniform bloom on a new building is normal water loss and often weathers away. Heavy or recurring deposits mean water keeps arriving, and near ground level the source may be groundwater, including salts drawn up by capillary action. Streaks below a joint or crack point to a path.

The association’s advice is to repair the moisture source before cleaning, because cleaning alone does not stop the water. Most deposits come off with dry brushing, then flushing with clean water, and harsher chemical methods are a last resort that should be tested on a small area. Painting over efflorescence hides the evidence without removing the moisture behind it. Fuzzy, dark, or musty growth is a different problem and belongs under the mold answer below.

Exterior work means excavating down to the footing, repairing and coating the wall, adding a drainage layer, and installing a perimeter drain wrapped in geotextile that leads to a daylight or storm outlet. Building Science Corporation prefers keeping water away from the wall over relying on a coating to be perfect. University of Minnesota Extension calls exterior work the most costly but most effective approach. The trade-offs are the excavation beside the house, the landscaping, decks, and patios in the way, buried utilities, and the permit questions that come with deep digging.

Interior work is a drain along the inside of the footing or slab edge, a drainage layer on the wall, and a sump pit with a pump. Building Science Corporation describes interior drainage as a retrofit option for existing leaking basements and says the interior drainage layer has to be airtight and vapor tight. Interior systems do not stop water pressure; they relieve it, and they usually depend on a pump.

Neither works if roof water and grading still send water to the wall. Where the water table is high and dewatering is not practical, Building Science Corporation says waterproofing is the only strategy. A geotechnical engineer’s opinion is reasonable before major work.

Water enters the pit from a perimeter drain or from gravel under the slab. When the level rises, a float or sensor starts the pump, a check valve keeps the water from running back, and the discharge pipe carries it away. Building Science Corporation says the pump should have a battery backup and an airtight lid, because power outages often coincide with heavy rain and the lid keeps soil gases out. Minnesota Extension also calls for a sealed, childproof cover and warns plainly that the pump can fail.

The discharge matters as much as the pump. A Building America footing drain guide describes a discharge pipe sloping downward at least a half inch for each foot over the first 10 feet. Sump water generally should not go into the sanitary sewer: King County, for one, encourages owners to disconnect downspouts, yard drains, and sump pumps from the sewer because rain in the sewer raises overflow risk. Rules differ by city and sewer district, and discharge onto a neighbor’s property raises its own problems, so confirm the approved outlet before installing.

Test the pump at the start of each wet season, clear the pit, and check that the float moves freely. A sump is a way of managing water, and a pump failure during a storm is the reason backup power and an alarm are worth asking about.

University of Minnesota Extension says a membrane or coating on the interior, without providing drainage, generally will not solve the problem in the long term. The reason is where the coating sits: on the dry side of a wall that is wet on the other side. Under pressure, water finds hairline cracks and pores, and salts can crystallize behind the film and push it off.

Where coatings do belong is as part of a system. Building Science Corporation describes damp-proofing applied on the exterior of a below-grade wall, often a fluid-applied bitumen, working together with drainage, a perimeter drain, and a capillary break over the footing. That is a different use from brushing a masonry paint on the inside of a wet wall.

Before any coating goes on, rule out condensation, which a coating will not fix, and check roof water, grading, and groundwater. Painting also hides efflorescence and staining that are useful evidence. If a product is on the table, ask to see its data sheet for what it is rated for, including whether it is meant for active water or only damp surfaces, and read what it says about surface preparation.

Bulk water comes first. Building Science Corporation says there must be good drainage away from crawlspaces, and that a crawlspace floor below surrounding grade needs perimeter drainage just like a basement. It calls for a continuous, sealed ground cover of vapor-resistant material over the soil, with a capillary break at the top of the footing.

On vents, Building Science Corporation is blunt: it describes traditional vented crawlspaces as often damp, moldy, and home to pests, and recommends against venting crawlspaces to the exterior, treating them instead as conditioned space with insulated perimeter walls. Washington’s building and energy codes set what is permitted and how it is documented, so sealing or changing vents is a question for the local building department, not just a contractor’s preference. A crawlspace with standing water or an active leak is not ready to be sealed.

Mold follows moisture. EPA says the key to mold control is moisture control, that wet materials should be dried within 24 to 48 hours, and that cleaning mold without fixing the water problem means it will likely return. It also says mold cannot be eliminated indoors entirely, and suggests professional help for large areas or contaminated water.

The basic build is a trench lined with fabric, a layer of clean washed stone, a perforated pipe, more stone, and the fabric wrapped over the top. A Building America footing drain guide describes a bed of clean half-inch to three-quarter-inch gravel with the pipe slightly sloped toward a single collection or discharge point. Water in the soil moves into the stone and pipe because that is the easier path, and the slope carries it to the outlet.

The names are about location and purpose. A footing drain runs outside the foundation footing, below the slab or crawlspace floor, to protect the basement. A curtain drain is the same trench in the yard uphill of a house, intercepting groundwater before it arrives. A surface drain, or catch basin, is a grated inlet that takes water from a lawn, driveway, or patio into a solid pipe. A downspout tightline is a solid pipe that carries roof water to an outlet.

Mix-ups cause failures: a perforated French drain is a poor way to handle roof water, because it can put that water back into the soil next to the house, and a surface problem needs inlets, not buried stone. Contractors and cities use these names loosely, so ask what water each drain is meant to collect and where it goes.

The residential code says surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection that does not create a hazard. In practice the options are a storm connection, spreading water across vegetated ground, an infiltration trench, dry well, or rain garden where the soil allows it, or a tightline to a public or private system. Federal Way’s single-family drainage bulletin names infiltration as the preferred method, with trenches, drywells, dispersion, and tightline connections as alternatives, for projects that need drainage plans.

The sanitary sewer is different. King County asks owners to keep rain out of the sewer system by disconnecting downspouts, yard drains, and sump pumps, because stormwater raises the chance of overflows. Some older neighborhoods still have stormwater connected to sewers, so ask the city or sewer district before connecting any drain to any pipe.

Permits depend on what you build. Federal Way’s bulletin, dated 2016, ties drainage plans to projects that create at least 2,000 square feet of new hard surface, and other cities use different triggers. Steep slopes and critical areas tighten them further. Washington law requires a call to 811 at least two business days before digging. Separately, the city can say whether the work needs drainage review. Look up city specifics through the service area pages.

Glacial till is a dense, compact mix of clay, silt, sand, and gravel left by the ice sheets, and water moves through it slowly. Perched water is the key idea: rain soaks into the looser soil above a dense layer, then sits or moves sideways instead of draining down. That is how a yard stays soggy in March, and how seepage turns up on a slope face or in a basement wall.

Local guidance expects testing, not assumptions. Ecology’s rain garden handbook says to test soil drainage in the wet season when possible, and that if the rate is below 0.1 inch per hour a different location should be considered. It also says to relocate if winter groundwater rises within a foot of the excavated bottom. Federal Way’s bulletin makes infiltration the preferred method on lots under 22,000 square feet unless soil or slope conditions preclude it, and asks for a soils infiltration report.

Not every lot is till. Some sit on sand and gravel that drain well, and valley soils can have high groundwater. A system tested in dry weather can look fine and fail in January, so ask when the test was done. If infiltration does not work, piped conveyance or dispersion is the usual fallback.

This is section R401.3 of the International Residential Code, as reproduced in Seattle’s 2021 residential code: lots are graded to drain surface water away from foundation walls, the grade falls not fewer than 6 inches within the first 10 feet, and impervious surfaces within 10 feet of the foundation slope not less than 2 percent away from the building. Where lot lines, walls, slopes, or other barriers prevent that, drains or swales are built to move the water. Minnesota Extension suggests a similar rule of thumb: an inch of fall for each foot over at least the first 6 feet.

The reason is simple: water that pools against a foundation becomes groundwater against the wall. Common mistakes are mulch or soil built up against siding, planting beds that act as basins, a walkway or patio that tilts toward the house, and downspouts that dump at the corner. Minnesota Extension adds that a downspout without an extender or splash block is worse than none.

Grading does not remove groundwater, and some lots cannot meet the numbers because the house sits below the neighbor or the side yard is narrow. In those cases a swale or drain is the answer, and the outlet question applies. A new patio or walkway should be poured with fall away from the house.

The Building America footing drain guide stresses clean washed stone because silt and sand clog the perforations, and wraps the gravel bed in fabric to stop the pipe filling with sediment. Fabric helps, but in very fine silty soil even fabric can slowly clog, which is one reason designs differ by soil and why a designer should know what the trench runs through.

The usual failures are sags that collect sediment, pipe crushed by backfill or heavy loads, tree roots seeking water, and an outlet that is buried or blocked with leaves, soil, or ice. A pipe laid flat never drains well. University of Minnesota Extension notes that existing footing drains can fail from collapse, clogging, or broken connections to a sump.

Maintenance is mostly watching. Keep outlet ends and catch basin grates clear. Where cleanouts were installed, they allow flushing and camera inspection. After a heavy rain, check that the outlet flows. New wet spots, sinkholes, or a basement that was dry and now is not, are signs the system needs attention. Keep a sketch of where the drain runs, because buried pipe is hard to find later and has to be located before anyone digs.

In Currens v. Sleek (Washington Supreme Court, 1999), the court declined to replace the common enemy doctrine with a reasonable use rule. Under it, landowners may alter the flow of surface water on their property, subject to three limits the court restated: a natural drainway must be kept open, surface waters may not be artificially collected and discharged upon adjoining lands in quantities greater than or in a manner different from the natural flow, and owners must exercise their rights with due care, acting in good faith and avoiding unnecessary damage to the property of others.

The classic problem is a drain or tightline that gathers water from roofs and yards and ends at the property line, turning scattered runoff into a stream on the neighbor’s lot. Spreading water across your own vegetated ground, or sending it to a storm system with approval, is the safer design. Photograph conditions before work, talk to the neighbor early, and keep records of what was built.

City codes often add drainage rules on top of the court’s rules, and a dispute is a legal matter. This answer cites one court decision and is general information; check with the city and an attorney before acting on a specific dispute.

The American Society of Concrete Contractors, citing ACI 301, says concrete should not be placed while rain, sleet, or snow is falling unless protection is provided, and that precipitation must not add to the mixing water or damage the surface. Contractors protect fresh concrete with plastic sheeting, remove standing water with a hose or squeegee, and avoid working rainwater into the surface finish. Rain on well-hardened concrete is not the concern; the risk is during placement and finishing.

The problem is the surface. The top layer takes the wear, and extra water there makes it weaker. The same society says remedial work may be needed for a rain-damaged slab, that grinding or removing a thin layer can restore many of them, and that some engineers question the durability of a slab with a layer taken off. Soft, muddy subgrade and water standing in the forms are separate problems that need fixing before the truck arrives.

Ask the contractor for the rain plan: what covers are on site, who watches the forecast, and when the pour will be postponed. Rain delays are normal in a wet climate, and a postponed pour is usually better than a repaired surface.

For cold, the National Ready Mixed Concrete Association defines cold weather as a period of more than three consecutive days with an average daily temperature below 40°F. It says concrete should be protected from freezing until it reaches 500 psi, which takes longer the colder it is, and that fresh concrete freezes if its temperature falls below about 25°F, which can cost it more than half its potential strength. Western Washington winters are more wet than frozen, so these steps matter mostly for cold snaps. The winter pouring guide covers it in full.

Heat is its own problem. The same association describes hot weather as any combination of high air or concrete temperature, low humidity, wind, and sun that speeds moisture loss. Water demand rises, setting speeds up, and plastic shrinkage cracks can form before the concrete sets. Its precautions include scheduling cooler hours, dampening the subgrade, windbreaks and sunshades, starting curing as soon as finishing is done and continuing for at least three days, and not adding water beyond the mix design.

These are guides, not cliffs. A dry, breezy, sunny day can behave like hot weather even when the air is not extreme.

The wet season is when the problem exists. Ecology’s rain garden handbook advises testing groundwater and soil drainage in the rainy months, December through April, when possible, because that is when conditions are worst. Winter is the time to watch the site: where water runs and ponds during a storm, whether downspouts overflow, and where the basement or crawlspace shows dampness. Photos and video from a storm are useful evidence for a designer.

The dry months are easier for the work. A trench or footing excavation can be dug, drained, and backfilled without pumping out groundwater, soil is easier to handle, concrete can be placed and cured without rain, and there is less mud and sediment to control. Wet-weather excavation means open trenches that fill, slopes that can slide, and erosion control. Some jurisdictions limit clearing and grading in the wet months, so ask.

Scheduling follows. Wet weather delays excavation, so a basement that floods every winter is often diagnosed in winter and scheduled for the next dry window, with temporary measures in between. Whatever the season, a call to 811 comes at least two business days before any digging.