HD Landscape and Maintenance builds retaining walls in Portland, OR — segmental block, boulder, and concrete walls engineered for the city’s slopes and rainfall. Portland requires a building permit for any wall over four feet or carrying a surcharge, and city code assumes full hydrostatic pressure unless drainage is installed. Oregon LCB #9977.
By Donavan Hesedahl, Owner/Operator · Last updated July 2026
Portland’s threshold is specific and it catches people, so start here.
Under Portland City Code Title 24, Chapter 24.70, a building permit is required for all retaining walls over 4 feet in height measured from the bottom of the footing to the top of the wall, and for any retaining wall supporting a surcharge — regardless of height.
Two details do most of the damage:
The measurement starts at the bottom of the footing, not at grade. You might see three feet of block face after backfill and landscaping. If the footing sits a foot below finished grade, the code-measured wall is four feet. A wall designed to avoid a permit frequently needs one once actual footing depth and final grade are pinned down. This is why we set elevations before pricing rather than measuring an existing face with a tape.
Surcharge removes the height exemption entirely. A surcharge is any load behind the wall beyond level earth backfill — a driveway, a patio, a structure, stored material, or an ascending slope. Portland’s exemption language excludes walls supporting ascending slopes steeper than 3:1 or any non-soil surcharge. On a hillside lot, the wall is almost always carrying a surcharge, which means the four-foot number is irrelevant and a permit applies at any height.
Beyond the wall itself, three related triggers come up constantly on Portland sites:
Complex sites and anything involving slope stabilization can also require a Site Development permit. BDS general inquiries: 503-823-7300.
This is the most useful thing on this page, and it comes straight out of the code rather than from marketing copy.
Portland’s Title 24 states that retaining walls must be designed to support the weight of the full hydrostatic pressure of undrained backfill unless a drainage system is installed.
Read that again, because it’s the whole argument. The code’s default assumption is that your backfill is saturated and pushing on the wall with the force of standing water. Drainage isn’t a best practice or an upgrade line item — it’s the thing that lets a wall be designed for soil pressure instead of water pressure. Skip it and you haven’t built a cheaper wall; you’ve built a wall designed for the wrong load.
In a climate where the Willamette Valley takes months of sustained rain onto heavy clay soils that drain slowly, that saturated condition isn’t hypothetical. It’s most of the winter.
So the failures we get called out to look at are almost always water, and almost always the same four things:
Two more code provisions worth knowing if you’re comparing bids, both from Title 24:
If a bid doesn’t itemize drain rock, drain line and outfall, geotextile, and compacted backfill in lifts, you’re not comparing walls — you’re comparing the visible face of two different structures.
There’s no universally best material. There’s a best material for a given height, surcharge, soil, access, and budget.
Segmental retaining wall (SRW) block — the default for most Portland residential work. Modular concrete units, dry-stacked, with geogrid reinforcement tied back into the soil mass on taller walls.
Boulder / rock walls — stacked basalt, common throughout Multnomah County.
Poured or CMU concrete — reinforced cast-in-place or block-and-grout.
Timber — pressure-treated dimensional lumber or ties.
For a hillside lot specifically: the deciding factors are usually surcharge and access, not aesthetics. An ascending slope above the wall means surcharge, which means engineering, which usually means segmental with geogrid or reinforced concrete. Boulder walls work beautifully on hillsides where a machine can get in and the wall can be built with real footprint depth. On the steep West Hills and Southwest Portland lots where neither is true, poured concrete is often the only option that fits.
Retaining walls are priced by square foot of exposed face, then adjusted heavily for everything behind it. The face is what you see and roughly the smallest cost variable.
What actually drives the number:
We quote after establishing actual footing elevation and finished grade, because that measurement determines whether the project is permit-exempt — and that’s the single largest step change in cost.
We’re based in Aloha and work throughout Multnomah County and the Portland metro.
Site conditions vary enormously across the city, and they drive the wall type more than budget does:
Outside Portland proper we serve Gresham, Beaverton, Tigard, Lake Oswego, Tualatin, Hillsboro, and Aloha, across Multnomah, Washington, and Clackamas counties. Note that permit thresholds differ by jurisdiction — Portland’s four-foot rule doesn’t automatically apply in Beaverton or Gresham, and we confirm the governing jurisdiction before designing.
Both Oregon LCB and CCB licenses authorize retaining wall construction — the LCB’s published scope covers planning, installing, maintaining, and repairing retaining walls. HD Landscape and Maintenance holds Oregon LCB license #9977. Note that Portland’s BDS retaining wall page references CCB licensure specifically, so confirm license acceptance with BDS for permitted work.
Yes, if the wall exceeds four feet measured from the bottom of the footing to the top of the wall, or if it supports a surcharge at any height. Surcharge means load beyond level earth backfill — a driveway, patio, structure, stored material, or an ascending slope steeper than 3:1. Walls over four feet also require stamped drawings and calculations from an engineer registered in Oregon. Because the measurement starts at the footing rather than at grade, walls that look under four feet often aren’t. Adding over 500 square feet of impervious area triggers stormwater requirements, and removing trees six inches or larger triggers Tree Plan review under Title 11.
It depends far more on drainage than on material. A properly drained segmental block or boulder wall should last 50 years or more. Reinforced concrete, properly drained and reinforced, is comparable or better. Pressure-treated timber in this climate is realistically 15 to 25 years. A wall of any material without functional drainage can begin failing within five to ten years, because it’s carrying hydrostatic load it was never designed for.
Water, in nearly every case. Portland’s own code assumes full hydrostatic pressure from undrained backfill unless a drainage system is installed — meaning a wall without drainage is designed for the wrong load from day one. The specific failure modes are missing or insufficient drain rock, a perforated drain line with no functional outfall, no geotextile between aggregate and native soil so clay silts up the drainage layer over several seasons, and native clay used as backfill instead of free-draining material. Months of sustained winter rain on slow-draining clay makes the saturated condition normal here rather than exceptional.
Effectively yes. Portland City Code Title 24 requires retaining walls to be designed for the full hydrostatic pressure of undrained backfill unless a drainage system is installed. You can technically build without drainage, but then the wall must be engineered for water pressure rather than soil pressure — a substantially heavier and more expensive structure. For any practical wall, drainage is the cheaper path: free-draining aggregate against the full height of the wall, a perforated collector line daylighted to a real outfall, and geotextile separating aggregate from native soil.
It depends on wall type and is a design output rather than a fixed number. Segmental walls follow the manufacturer’s buried-base-course rule — commonly around one inch of embedment per eight inches of wall height, on a compacted aggregate base, with a stated minimum. Engineered and concrete walls have footing depth and dimensions specified by the engineer based on soil bearing capacity and load. What matters for Portland homeowners is that footing depth directly determines permit status, since the city measures wall height from the bottom of the footing — so a deeper footing can push an apparently short wall over the four-foot threshold.
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 a.m. – 7:00 p.m. · Sunday, Closed
License: Oregon LCB #9977
Serving Portland and surrounding areas including Southwest, Southeast, Northeast, North, and Northwest Portland, plus Gresham, Beaverton, Tigard, Lake Oswego, and Multnomah, Washington, and Clackamas counties.