Concrete Retaining Walls in SeaTac, WA

Retaining walls in SeaTac: what to know

SeaTac’s no-permit list names retaining walls and rockeries up to 4 feet high, with the height counted from the footing’s underside to the wall’s top edge. Two exceptions move a wall out of that item: a surcharge resting on it, and any Class I, II, or III-A liquid it holds back. The clearing code also exempts on-site excavation for basements, footings, and retaining walls, but that exemption does not reach fill made from the excavation, or an unsupported height over four feet once the structure is complete.

Cut and fill beyond those exemptions fall under the clearing code’s limits. Excavation under four feet in vertical depth, with no more than 50 cubic yards of earth, is exempt, and fill under three feet in vertical depth within the same volume is too. Separately, the erosion and sediment control section reaches any activity that will clear, grade, or otherwise disturb the site, permit or not.

Permits and rules in SeaTac

Before we quote a wall, we confirm with the city how it measures height, whether a surcharge or a held liquid applies, and which permit path the wall needs. Walls outside that no-permit item we take to the city for an answer on the address. The erosion and sediment control requirement applies to each site as well, and we confirm its scope before the first cut.

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

How we approach it

Set the wall height from the footing’s base up to the top edge before designing it
Note any surcharge and any held liquid before choosing the wall type
Check that the cut stays inside the clearing code’s depth and volume limits
Put erosion and sediment control in place before the first cut

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 SeaTac

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

Questions from SeaTac homeowners

Is a permit needed for a retaining wall in SeaTac?

A wall up to 4 feet high falls under the city’s no-permit item, except where a surcharge sits on it, or where it retains Class I, II, or III-A liquids. Walls outside that item go to the city for an answer on your address, and we confirm that answer before we design the wall.

What is the tallest wall SeaTac lets you build without a permit?

The no-permit item stops at 4 feet, read from the footing’s underside up to the wall’s top. Walls that are taller, or that carry a surcharge or a held liquid, sit outside that item, and the city’s answer comes before we design one.

Does digging for a SeaTac wall need clearing and grading approval?

The clearing code exempts on-site excavation for basements, footings, and retaining walls, but not fill made from that excavation, or an unsupported height over four feet after completion. Cuts under four feet in vertical depth, with no more than 50 cubic yards of earth, are also exempt. We confirm the dig with the city before the ground is opened.