Retaining Walls contractor —
Seattle & Puget Sound.
Retaining walls fail when drainage gets ignored. We back-fill with drain rock, install perforated tile, and weep the wall properly so hydrostatic pressure doesn't push it over.
Retaining walls fail when drainage gets ignored. We back-fill with drain rock, install perforated tile, and weep the wall properly so hydrostatic pressure doesn't push it over. The most common failure mode in PNW retaining walls is water buildup behind the wall after winter rains.
Wall systems range from simple Allan Block segmental units (good for under 4 ft, no engineering required) to engineered poured-concrete and soldier-pile walls (any height, retaining structures or roads above). The wall type depends on height, soil, and what's on top.
What we build
SCOPE- 01Engineered design
- 02Allan Block / Versa-Lok
- 03Poured concrete
- 04Perforated drain tile
- 05Geogrid reinforcement
- 06Permit + inspection
Phased process
PROCESS- 01
Engineering
Geotechnical assessment and structural design for walls over 4 ft or retaining structures.
- 02
Permit
Permit required for walls over 4 ft, terraced walls, or those in critical areas.
- 03
Excavation
Excavate footing area, compact base, install gravel pad.
- 04
Build
Stack segmental units or pour concrete walls, install geogrid reinforcement at specified courses.
- 05
Drainage
Drain rock backfill, perforated PVC drain tile at base, weep holes through wall, filter fabric to prevent silt migration.
- 06
Backfill + finish
Compact backfill in 8" lifts, cap with topsoil, finish grade to drain away from wall.
Spec sheet
SPEC- +Segmental retaining wall: Allan Block, Versa-Lok, Belgard (concrete units)
- +Poured concrete with rebar reinforcement for engineered walls
- +Soldier pile + lagging for tall walls or near structures
- +Geogrid (Tensar, Mirafi) at specified courses
- +Perforated 4" PVC drain tile, gravel-wrapped
- +Filter fabric to separate drainage layer from native soil
- +Drain rock (1.25" minus) backfill
Cost drivers
COST- Height and length$40–$150/sf face area depending on wall type
- Engineering (walls >4 ft)+$2K–$8K for geotech and structural design
- Wall typeAllan Block $40–$70/sf → poured concrete $80–$150/sf
- Geogrid reinforcement+$5–$15/sf for taller walls (4–10 ft)
- Site access (steep slopes, hauling)+30–80% for difficult access
Codes & permits
COMPLIANCE- IRC R404 (retaining walls)
Walls over 4 ft (measured from bottom of footing to top of wall) require engineered design and permit.
- Seattle ECA / critical areas
Walls in steep-slope or wetland buffers require additional environmental review.
- Geotech recommendations
Engineering reports often dictate over-excavation depth, geogrid spacing, and drainage requirements.
Is retaining walls the right call?
- →Sloped lot terracing for usable yard space
- →Driveway or walkway grade transitions
- →Existing wall failure (leaning, cracked, displaced)
- →ADU or addition on sloped lot requiring level building pad
Walls questions
FAQQ.01
Do I need a permit for a retaining wall?
In Seattle and most Eastside jurisdictions: yes for walls over 4 ft. Some jurisdictions (Bellevue, Kirkland) require permit for any wall in a critical area regardless of height.Q.02
How long do retaining walls last?
Properly installed segmental walls: 40–60 years. Poured concrete with proper drainage: 60–100+ years. Without drainage, expect failure in 10–20 years from frost-heave and hydrostatic pressure.Q.03
What is geogrid and why do I need it?
Geogrid is a structural reinforcement mesh layered into the backfill at specified intervals. It ties the wall back into the soil mass behind it, dramatically improving stability for walls over 4 ft.Q.04
Can you build over an existing failed wall?
Rarely worth it — failed walls indicate drainage or base failure that compounds. We typically demo and rebuild with proper drainage, which is the only way to get a warrantable result.
Official resources & sources
- Source ↗IRC R404 — Foundation & retaining walls
- Source ↗WSEC 2021 Residential Energy CodeEnvelope, HVAC, hot-water and air-sealing requirements
- Source ↗WA HB 1110 — Middle housing lawStatewide middle-housing zoning preemption
- Source ↗WA HB 1337 — ADU statewide rulesTwo-ADU baseline, no owner occupancy, parking limits
- Source ↗WA Dept. of Commerce — ADU resources
- Source ↗WA L&I contractor license lookupVerify Golden State ADU Builders Inc · GOLDESA747LZ
- Source ↗Washington State Building Code CouncilStatewide adopted codes (IRC, IBC, WSEC)
Ready to scope your walls project?
Send a paragraph and the address. A licensed PM replies within one business day with next steps.
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