HD Landscape & Maintenance builds segmental block and natural stone retaining walls across the Portland metro — engineered drainage behind every wall, permits and stamped calculations handled where the height or load requires them. Oregon LCB #9977, licensed, bonded and insured.
By Donavan Hesedahl, Founder & Owner · Last updated July 2026
Two triggers, and the second catches far more people than the first.
Under Portland City Code 24.70, a building permit is required for a retaining wall that:
Where a permit is needed, an engineer registered in the State of Oregon must provide stamped drawings and calculations for any wall over four feet. You’ll also need a site plan showing property lines, easements, distances to buildings, wall placement, and any proposed paving.
Two things that catch homeowners out:
Terracing isn’t an automatic workaround. Building two three-foot walls instead of one six-foot wall sounds like it sidesteps the threshold. It often doesn’t — tiered walls spaced closely together surcharge each other, so the lower wall carries load from the upper one and the pair may be assessed together. If the tiers are close, expect them to be treated as one structure.
The wall may not be the only thing under review. Portland’s retaining wall guidance notes that adding more than 500 square feet of impervious area brings in a mitigation form or a stormwater plan — and wall projects usually arrive with a new patio, stair run, or driveway change attached. Tree removal is reviewed alongside clearing and grading permits under Portland’s Title 11 tree code, so mature trees near the excavation matter too.
Washington County applies a comparable four-foot threshold with level backfill, so the logic holds across Beaverton, Aloha, Hillsboro, and Tigard — but the review process differs by jurisdiction, and we confirm the right one for your address before quoting.
Yes, and it’s the part that determines whether the wall is still standing in fifteen years.
Here’s the physics. Willamette Valley clay holds water rather than draining it. Water trapped behind a wall exerts hydrostatic pressure, and saturated soil weighs far more than dry soil. A wall built without drainage stops being a retaining wall and becomes a dam — and it’s a dam designed for a fraction of the load it’s actually carrying. Portland’s own structural provisions require lateral design pressures to be increased where soils are expansive or the wall supports an ascending slope, which is a code-level acknowledgement of exactly this problem.
What a properly drained wall has behind it:
Almost none of that is visible when the job is done, which is precisely why it’s the first thing cut from a cheap quote. Ask any contractor to describe what goes behind the block before you compare prices.
Where a wall is solving a wider water problem, it works alongside drainage and grading rather than instead of it.
Segmental concrete block is the workhorse and what we build most. It’s engineered for the job, accepts geogrid reinforcement, flexes slightly with ground movement rather than cracking, and individual units can be replaced. For anything structural in this climate, it’s the default for good reason.
Natural stone, including locally quarried Columbia River basalt, suits lower walls and garden terracing, and looks considerably better doing it. Dense, regional, and durable.
Poured concrete makes sense for specific engineered situations, though it’s less forgiving of ground movement and any crack is permanent.
Timber deserves a warning. Pressure-treated timber walls are cheap up front and have a genuinely finite life in a climate this wet — they rot at grade, where the wood meets permanently damp soil, and the failure is structural rather than cosmetic. If you’ve inherited a timber wall that’s leaning or spongy at the base, that’s the end of its life rather than a repair.
One more Oregon-specific factor: the entire Portland area sits in Seismic Design Category D, the highest routine category. Engineered walls here have to account for lateral loads from earthquake motion, not only from soil. It’s another reason stamped calculations on a taller wall aren’t bureaucracy.
The building is rarely what sets the schedule.
Permitting and engineering are the real timeline. Stamped drawings take time to produce, and city plan review takes weeks rather than days. Add winter to that and it stretches further — excavating footings in saturated clay between November and March is slow work and hard on the rest of the property.
The practical implication: if you want a wall finished by summer, start the conversation in winter.
Quoted per project after a site visit, because the variables are unusually wide for this kind of work:
Written price before anything starts, and we don’t begin until you approve it. Call (971) 336-5520 or request a free quote.
We build retaining walls across the Portland metro, Monday to Saturday, from Aloha in Washington County.
Portland · Lake Oswego · West Linn · Beaverton · Hillsboro · Tualatin · Sherwood · Wilsonville · Clackamas · Newberg · Salem
Also serving Aloha and Tigard. The steeper lots in Lake Oswego and West Linn generate most of our wall work — grade change and mature trees in combination are what make those sites demanding.
Walls usually arrive alongside other work: see hardscaping and outdoor structures for patios and walkways, and our services hub for the full range. Finished projects are in the portfolio.
Verify our licence — LCB #9977 — through the Oregon Landscape Contractors Board public lookup. Oregon also puts the duty on us to pull the required permit before work starts, or to confirm in writing that you already have.
Do I need a permit for a retaining wall in Portland, OR?
Yes if the wall is over 4 feet measured from the bottom of the footing to the top of the wall, or if it supports a surcharge — a driveway, patio, building, or ascending slope — at any height. Walls over four feet also need stamped drawings and calculations from an engineer registered in Oregon. Terracing two smaller walls close together often doesn’t avoid the threshold, because the tiers surcharge each other.
How much does a retaining wall cost in Portland?
Cost is driven by height (and whether that height triggers engineering), length, whether the wall carries a surcharge, material choice, excavation and clay disposal, drainage and geogrid, and site access. We quote in writing after a site visit. Call (971) 336-5520 with your address for an honest range.
What retaining wall material lasts longest in the rainy climate?
Segmental concrete block, which is engineered for the load, accepts geogrid reinforcement, and flexes with ground movement instead of cracking. Locally quarried basalt is excellent for lower garden walls. Pressure-treated timber has a genuinely finite life here — it rots at grade where the wood meets permanently damp soil.
How long does it take to build a retaining wall?
A short garden wall takes a few days; a structural wall under four feet roughly one to two weeks; taller or terraced walls longer. Permitting and engineering set the real timeline — stamped drawings plus city plan review run into weeks. Winter excavation in saturated clay is slower again, so start the conversation months ahead.
Do you handle drainage behind the retaining wall?
Yes — drain rock behind the block, a perforated pipe at the base daylighted to a real outlet, geotextile keeping clay out of the drain rock, backfill compacted in lifts, and geogrid on taller walls. In Willamette Valley clay this is what stops a wall becoming a dam. It’s also invisible once finished, which is why it’s the first thing missing from a cheap quote.
HD Landscape and Maintenance LLC 6581 SW 192nd Ave Aloha, OR 97007
Phone: (971) 336-5520
Email: hdlandscapellc@gmail.com
Hours: Monday–Saturday, 7:00 am – 7:00 pm · Sunday closed
Oregon LCB Lic. #9977 · Licensed & Insured
Serving the Portland metro area including Portland, Beaverton, Aloha, Tigard, Tualatin, Lake Oswego, Hillsboro, West Linn, Wilsonville, Sherwood, Clackamas, Newberg, and Salem.