Concrete Retaining Walls in Mountlake Terrace, WA

Retaining walls in Mountlake Terrace: what to know

The footing depth goes on the record first, since wall height is counted from the footing to the top of the wall. Under the state exemption, a wall not over four feet high qualifies when no surcharge bears on it and it retains no Class I, II, or III-A liquid. Slopes, driveways, and structures that press against the back of the wall are drawn on the site plan, since a sideways load falls within the state rule’s definition of a surcharge, and any surcharge takes a short wall outside the exemption.

The city adopts the 2018 International Building Code with state amendments, and its replacement for the code’s exemption list names only small sheds. We read that list as leaving the wall exemption in doubt, so we ask the building counter before a short wall is kept out of the permit track. The drain behind the wall is shown on the section, with the outlet set on ground that takes the water away from the footing.

Permits and rules in Mountlake Terrace

We measure each wall from its footing, sort its loads, and compare its placement against the state exemption. We confirm the building-counter answer for any wall under four feet before excavation is planned. When the counter asks for engineering, we bring in a professional engineer qualified to practice in Washington and start that work early.

Rules change and vary by parcel, so we confirm the current requirements with the city before we start.

How we approach it

Record footing depth on the first sheet
List each surcharge, including slopes and structures
Ask the building counter about short walls
Draw the drain layer and outlet on the section

For the full process, see our Retaining Walls page.

Building in the cold months? See our guide to winter concrete pours.

Our retaining walls work, serving Mountlake Terrace

Examples of our work. We build retaining walls in Mountlake Terrace and the cities around it. See all of our work

Questions from Mountlake Terrace homeowners

What does the state exemption cover for a Mountlake Terrace wall?

The state exemption reaches a wall whose height from footing to top is no more than four feet, provided no surcharge loads it and it holds back no Class I, II, or III-A liquid. Whether the city’s building code amendment keeps that exemption is an open question we confirm with the counter.

Does a driveway behind a Mountlake Terrace wall count as a surcharge?

Anything pressing on the back of the wall, be it a driveway, a slope, a bank, or a structure, pushes sideways and is treated as a surcharge by the state rule. Even a low wall loses the exemption once a surcharge is on it.

When does the counter ask for engineering on a Mountlake Terrace wall?

We do not assume it does. If the counter calls for engineering, we book a professional engineer qualified to practice in Washington at once, so the schedule does not hinge on a late reply.