South King County
Paver Patios in Des Moines, WA
Quick answer
On a Des Moines bluff lot, where the patio runoff goes matters more than where the patio goes. Adding impervious surface above a slope that already sheds groundwater at the Lawton Clay contact is how movement starts, so the field gets collected and tightlined inland. We are fifteen minutes west of the Kent shop.
West of Marine View Drive the stratigraphy runs everything. It's the classic Vashon sequence: a dense till cap over advance outwash sand, sitting on Lawton Clay. Rain works down through the sand, meets clay it can't pass, and turns sideways at that contact. Where that groundwater daylights is where the bluff face moves. You can read the record in the leaning alders below Woodmont and Redondo. A patio is impervious surface, and impervious surface concentrates water. On the west side of a lot here, the drainage plan is the project. We pitch the field inland, collect it in a catch basin, and carry it in solid pipe to a legal discharge point away from the slope. It never gets to sheet toward the crest.
That means paperwork before shovels. Landslide, erosion and steep-slope hazards are mapped along the shoreline and back into the Des Moines Creek and Woodmont ravines. Grade or excavate inside those areas or their buffers and the city typically wants a report from a licensed geotechnical engineer. Within 200 feet of the ordinary high water mark you are in the city Shoreline Master Program. A patio in that band can need a shoreline exemption, and the review runs longer.
The design brief flips what we hear inland. People bought for the water, Maury Island, the Olympics behind it. So the instruction is keep everything low. Seat walls at eighteen inches instead of screens. Planting that tops out below the sightline from the deck. Evergreen structure that still reads in February. Salt narrows the list further. Kinnikinnick, salal, evergreen huckleberry, hebe and carex hold up on a windward bluff-top corner where a hydrangea burns brown. Then there's access. The original 25 and 50 foot platted lots come with narrow streets and short driveways. So we phase deliveries and stage on the property. No flatbed sits at your curb for a week.
What’s different about Des Moines
Des Moines is the one place we work where a patio can be a slope-stability question. That marine bluff already sheds groundwater at the till and clay contact. Pile new roof and surface water on top of it and that's the mechanism that moves it. So we design the outfall before anybody picks a paver.
Paver Patios cost in Des Moines
| Item | Typical range | Unit |
|---|---|---|
| Standard concrete paver patio, running bond or herringbone | $22-$30 | per sq ft |
| Premium or large-format paver patioTecho-Bloc and Belgard slab lines, tighter tolerances and more cutting. | $30-$45 | per sq ft |
| Dry-set natural flagstone patio | $38-$60 | per sq ft |
| Over-excavation and structural fill on a soft subgradeDigging, haul-off, and imported rock combined. | $60-$95 | per cubic yard |
| Paver seat wall integrated into the patio edge | $65-$110 | per linear ft |
| Channel drain with piped outfall to daylight | $45-$85 | per linear ft |
These are typical installed ranges for the Puget Sound market and include labor, base, and materials; the number that ends up on your proposal comes from a site walkthrough where we can see access, grade, and what the subgrade is actually made of. Bids around $15 a square foot exist here and they are usually the same pavers over four inches of base instead of eight to twelve, laid on fabric-free subgrade. On Alderwood till that is the difference between a flat patio and a wavy one by the third winter.
Permits in Des Moines
Permits go through City of Des Moines Planning, Building and Public Works. The standard Western Washington threshold applies. A retaining wall over 4 feet, measured from the bottom of the footing to the top of the wall, needs a building permit and stamped structural engineering. A surcharge can pull a shorter wall into review too. That means a driveway, a structure above, or a stacked tier. Des Moines adds two layers that matter more here than almost anywhere else we work. First, geologically hazardous areas. Landslide, erosion and steep-slope hazards are mapped along the marine bluff and the ravines. Grading, walls or significant excavation inside those areas or their buffers typically needs a report from a licensed geotechnical engineer on top of the structural work. Second, the Shoreline Management Act. Property within 200 feet of the ordinary high water mark of Puget Sound falls under the city Shoreline Master Program. There a patio, wall or grading project can require a shoreline exemption or a substantial development permit, and the review timeline stretches accordingly. Added hard surface can trigger stormwater review as well. These thresholds get revised, so we confirm with the city at permit time before we commit to a scope.
Paver Patios in Des Moines: questions
Can I build a paver patio on a bluff lot in Des Moines?
Often yes, once the drainage and the geotechnical question are answered. What we won't do is add several hundred square feet of impervious surface uphill of a marine bluff and let it discharge toward the crest. The build we do recommend pitches the field away from the slope, collects it, and carries it in solid pipe to an approved outfall. Inside the mapped landslide and erosion hazard areas the city generally wants a licensed geotechnical engineer involved. That report shapes the layout. It doesn't just rubber-stamp it.
Does the Shoreline Master Program apply to a back yard patio?
It can. Property within 200 feet of the ordinary high water mark of Puget Sound sits inside the city shoreline jurisdiction. A patio, wall or grading project in that band may need a shoreline exemption or a substantial development permit. It's a timeline issue more than a cost issue, but it's a real one. It's also the single most common surprise for people buying near Redondo or the Marina District. We check the parcel against the shoreline mapping with City of Des Moines Planning, Building and Public Works before we commit to a schedule.
My street is narrow and the driveway is short. How do you stage the work?
We plan it on day one. On the old platted streets we phase deliveries, so a pallet load isn't sitting where a neighbor parks. Material gets staged on the property where there's room for it. The machine gets sized to the driveway, not to the job. Some Des Moines back yards genuinely are wheelbarrow access. When that's the case we say so at the walkthrough and price the labor honestly, instead of finding out in week one.
What does a paver patio cost in Des Moines?
For the Puget Sound market in 2026, figure roughly $22 to $30 per square foot installed for a standard concrete paver field. Large-format or premium units run $30 to $45. Those are planning ranges, not a quote. Des Moines adds two cost drivers other cities don't have. Restricted access on the older narrow-lot streets shifts work off the machine and onto hands. And a bluff-side lot needs piped drainage, commonly $45 to $85 per linear foot for a channel drain with a piped outfall. Where geotechnical review is required, that's a separate consultant cost.