Permeable Resin-Bound Surfacing in Seattle, WA

The 2026 Stormwater Code, SPU's materials list and the facility credit

Seattle's Stormwater Code is Title 22, Subtitle VIII of the Municipal Code, applied through a Stormwater Manual issued as joint SDCI and SPU Director's Rules. The 2026 code and manual became effective on July 1, 2026, under Ordinance 127444.

For materials, SPU publishes an allowable permeable pavement wearing course list for stormwater credit, last dated September 2016. It covers pervious concrete, porous asphalt, named paver and grid systems and one flexible porous mat, asks the designer to confirm initial surface infiltration above 100 inches per hour, and keeps the city's right to approve or decline systems site by site. A poured resin-bound surface isn't on the list, so ask SDCI and SPU how they would review it before counting it toward code compliance.

SPU's Stormwater Facility Credit Program discounts the drainage fee on the King County property tax bill for privately owned systems, permeable pavement included, that slow or treat runoff. SPU says single-family homes typically don't have systems that qualify. Credits are site specific, capped at 50 percent under SMC 21.33.040, and applications received by November 1 count toward the next year's bill.

Till, combined sewers and steep lots

Much of Seattle sits on dense glacial till with pockets of more permeable outwash, so infiltration can change from one block to the next. Where testing shows slow soils, the engineer may add an underdrain or treat the resin-bound area as a surface that drains to another facility rather than as an infiltrating practice. Long, wet winters mean the open-graded base has to stay free-draining for months at a time.

Older parts of the city drain to combined sewers, and steep slopes and landslide-prone ground are regulated as environmentally critical areas, which can limit infiltration near slopes and foundations. Fill on former industrial land along the Duwamish may need a liner where contamination is present. These are calls for the project engineer and SDCI's drainage reviewers.

Where it fits in Seattle

• Townhouse and rowhouse infill in neighborhoods such as Ballard, Columbia City and the Central District, where shared walks and courtyards sit on private land.
• Green Factor landscapes. SDCI's Green Factor score sheet, required in multifamily, commercial and some other zones, gives credit for permeable paving; how a resin-bound surface scores is the reviewer's call.
• Campus and hospital grounds on First Hill and in the University District, for plazas and walks set back from public sidewalks.
• Single-family patios and paths where an owner wants a porous surface that can be designed to infiltrate.
• Tired concrete. Over an existing slab resin-bound is a resurfacing, not a stormwater facility; see concrete resurfacing in Seattle.

Keep it out of planting strips, sidewalks and driveway aprons in the right-of-way unless SDOT approves the material under a Street Use permit.

Permits, reviewers and how Resin Rock fits in

SDCI issues permits and runs drainage review on private property. Its paving guidance counts permeable paving as hard surface, requires a grading permit once you add or replace 750 square feet or more of paving, and requires a civil engineer above 5,000 square feet of new or replaced paving. SPU runs the facility credit, and SDOT controls the right-of-way.

Resin Rock is a manufacturer-supplier of UV-stable resin binder, natural stone aggregate blends, trims and Rock Crete permeable sub-base. Our technical data sheets support your engineer's submittal. We don't install; we train and approve installers and can match you with an approved installer, usually within 24 hours.