Hardscaping
Paver Patios in Kent & Greater Seattle
Quick answer
A paver patio is an interlocking concrete or stone surface set on a compacted crushed-rock base rather than a poured slab. In King County, installed cost typically runs $22 to $38 per square foot depending on the paver, base depth, and site access. Blue Landscaping designs and builds every patio in-house.
Most failed patios in South King County did not fail at the surface. They failed six inches down, where a thin base sat on undisturbed glacial till and had nowhere to send water. Alderwood series soils carry a cemented hardpan layer that behaves like the floor of a bathtub, so November rain collects under the pavers, softens the bedding course, and by March the field has a low spot that ponds after every storm. Correcting that later means pulling the whole surface and starting over.
Our builds start with excavation down to native soil, usually 9 to 12 inches below finished grade on a residential patio and deeper anywhere the subgrade pumps under a plate compactor. Woven geotextile separates soil from rock so fines cannot migrate up and contaminate the base. Crushed 5/8-inch minus then goes in lifts of no more than four inches, each one compacted damp, with a steady quarter-inch-per-foot fall running away from the house. That pitch is invisible underfoot. It is also the whole difference between a dry patio and a mossy one.
Design happens at our Kent shop rather than at a supplier counter, and the people who draw the layout are the people who set the stone. No hardscape sub sits in the middle to lose the detail about how the soldier course meets a door threshold, or why the drain line has to daylight past the property corner instead of into the neighbor grade. When the sod comes off and something on the plan turns out to be wrong, you get an answer that morning, not after three phone calls.
What’s included
- Site layout with grade shots and a Washington 811 utility locate before anything is dug
- Excavation to native subgrade, typically 9 to 12 inches below finish grade, with spoils hauled off
- Woven geotextile separation fabric over till, clay, and silt subgrades
- Crushed 5/8-inch minus base placed in 3 to 4 inch lifts and plate-compacted at each lift
- One-inch screeded bedding course of clean angular chip, never rounded mason sand
- Paver field laid to the chosen pattern with wet-saw cuts at all edges and obstructions
- Concrete toe or heavy PVC edge restraint spiked at 10 to 12 inches on center
- Polymeric sand swept, watered in per manufacturer instructions, and re-topped after it sets
- Surface drainage tie-in: channel drain, catch basin, or solid pipe carried to daylight
Materials we use
- Mutual Materials Holland, Dublin Cobble, and Roman Paver units in Seattle-stocked colors
- Belgard Cambridge Cobble and Mega-Arbel slabs
- Techo-Bloc Blu 60 and Aberdeen for large-format modern fields
- Basalite Nantucket and Cobblestone pavers
- Crushed 5/8-inch minus base rock from Maple Valley and Auburn pits
- Mirafi woven geotextile for subgrade separation
- Techniseal HP NextGel or Alliance polymeric jointing sand
- NDS channel drain and catch basin components with 4-inch solid SDR-35 outfall pipe
How the build runs
- Step 1
Site walk and in-house design
We measure the yard, shoot grades off the door threshold and the low corner, and find where water currently goes. You get a layout with real dimensions, a paver and pattern selection, and a scope that names the base depth we intend to build.
- Step 2
Locates, layout, and protection
Public utilities get located through Washington 811 and private lines get traced separately. The crew paints the footprint on the ground so you can walk it at full size, then sets plywood runs and plastic to keep the lawn and siding intact.
- Step 3
Excavation and subgrade proof
Sod and topsoil come off to native. We walk the exposed subgrade behind the compactor looking for soft spots that rebound or pump water. Anything that moves gets over-excavated and replaced with structural rock before we go any further.
- Step 4
Base build and compaction
Geotextile goes down, then crushed rock in thin lifts. Each lift is watered and run with a reversible plate until the machine stops sinking and starts riding. Grade is checked with a laser at every lift so the pitch is built into the base, not faked in the sand.
- Step 5
Screed and set
One inch of angular chip is screeded off rails, never over-thickened to hide a bad base. Pavers are set off a string line from the most visible edge outward, pulled from three pallets at once so color variation blends across the field instead of banding.
- Step 6
Cuts, restraint, and jointing
Perimeter cuts are made on a wet saw, not split. Edge restraint locks the field, polymeric sand is swept and vibrated in, then activated with a light rain-setting pass. We come back to top off any joints that drop after the first cure.
- Step 7
Cleanup and walkthrough
Beds get restored, the driveway is blown and washed, and we walk the finished patio with you looking down the surface at a low angle where every high point shows. Anything that reads wrong gets lifted and reset before we load out.
Most residential patios between 300 and 700 square feet run three to six working days on site, plus a day or two when there are heavy cuts, a seat wall, or a subgrade that has to be over-excavated and replaced.
What it costs
Real installed ranges for the Puget Sound market, published so you can plan before anyone visits.
| 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.
Building this in the Pacific Northwest
Water has to leave the patio, not just soak through it
Kent valley floors take roughly 38 to 45 inches of rain a year, and the foothill edge toward Maple Valley and Issaquah can see four to six feet. Paver joints are not a drainage plan. The base needs positive pitch to a real outlet, downspouts need to be piped under the field rather than discharged onto it, and any patio tucked against a walkout basement gets a channel drain across the low side.
Alderwood till reads solid and drains like a countertop
The dense till under much of Kent, Covington, and Renton feels like a great subgrade in August and turns to grease in January. Water perches on the hardpan instead of percolating away. Separation fabric keeps the base clean, thin compacted lifts keep it stiff, and on the worst sites we run a perforated edge drain in washed rock at the downhill side of the base so the rock section can shed water instead of storing it.
Our freeze-thaw is shallow, frequent, and hard on wet base
The lowlands here rarely get a deep frost, but they cross freezing dozens of times between November and February. A saturated base that cycles that often will heave and relax repeatedly, which is what makes a patio go wavy in its second or third winter. Compaction and drainage matter far more locally than frost depth does. Segmental pavers also flex with that movement instead of cracking the way a monolithic slab does.
Permits and impervious surface accounting
Kent and most King County jurisdictions treat an at-grade patio as exempt from a building permit, though a deck-height or elevated patio changes that. Drainage review is a separate question: adding on the order of 2,000 square feet of new plus replaced hard surface is where the King County Surface Water Design Manual pulls a project into full review, and most cities here run an adopted version of it. Critical area, wetland buffer, and steep-slope setbacks override all of it, and we check those before design.
Paver Patios: common questions
Will a paver patio sink or heave through our winters?
Not if the base is right. Settlement almost always traces back to thin rock, lifts placed too deep to compact, or a subgrade that was never proofed. A properly built 9 to 12 inch compacted section on separation fabric, pitched to a real outlet, holds its shape. The advantage of pavers is that if a corner ever does move, we lift that section, correct the base, and reset the same units.
Pavers or a poured concrete slab?
Concrete is cheaper up front and it will crack. In this climate the question is only where and when. Pavers cost more initially, flex with seasonal movement, and can be opened up to run a gas line or fix a drain without a saw and a jackhammer. Concrete makes sense for large plain surfaces on stable ground. For anything shaped, sloped, or likely to be modified later, pavers age better.
Do I need a permit for a patio in Kent?
An at-grade patio generally does not need a building permit in Kent or the surrounding South King County cities. What can trigger review is total impervious surface, work inside a critical area or wetland buffer, retaining any grade over four feet, or a patio raised high enough to count as a deck. We confirm the specific thresholds with your jurisdiction before we finalize a layout.
How much slope do you build in, and will I feel it?
Standard is a quarter inch of fall per foot, running away from the house toward a planting bed, lawn, or drain. Across a 16 foot patio that is four inches total, which nobody notices underfoot and no patio furniture wobbles on. Flatter than an eighth inch per foot and water starts standing, especially once the surface picks up a little moss texture.
What keeps moss and weeds out of the joints?
Polymeric sand, properly activated, is most of the answer. It sets up firm and denies seeds a rooting medium. What actually causes joint growth here is organic debris: fir needles, maple leaves, and moss spores composting in the joint over a wet winter. Blow the surface a few times each fall, wash it in spring, and keep overhanging limbs trimmed back. Re-sanding every five to eight years is normal.
Can you build a patio in the winter?
Yes, and we do, though it depends on the site. Compaction needs moisture control, and a subgrade that is fully saturated will not proof out no matter how many passes we make. On well-draining sites winter work is fine and scheduling is easier. On heavy till with standing water we would rather wait for a dry stretch than bury a bad base under good pavers.
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