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Basement waterproofing in Spokane: what to check first

A wet basement is one of the most common reasons Spokane homeowners call a foundation contractor. Before you pay for a waterproofing system, it helps to know when water shows up, where it is coming from, and what the local rules say. Here is what the public sources show.

When Spokane basements get wet

Spokane is fairly dry overall. NOAA's 1991 to 2020 climate normals for Spokane International Airport show about 16.45 inches of precipitation a year. Most of it falls from November through January (about 2.06, 2.34 and 1.97 inches in those months), and the same station averages 45.4 inches of snow a year, with the most in December and January. That means winter rain and late-winter snowmelt are the times to watch your basement walls and floor most closely. If water only appears then, surface drainage is a good first suspect.

Start outside: grading, gutters and downspouts

The City of Spokane's Full Basement Wall Section guide sheet shows the ground sloping away from the foundation at least 6 inches within the first 10 feet, for drainage under the residential code (IRC R401.3). It also calls for dampproofing on the outside of basement walls (IRC R406.1). On an older home, the soil next to the house has often settled or been built up over time, so check that it still slopes away. Make sure gutters are clear and that downspouts carry water away from the house instead of dumping it next to the wall.

Where sump pump and downspout water can go

Spokane Municipal Code 13.03.0320 says: "No person may discharge or cause to be discharged any storm sewage into a sanitary sewer." Before a contractor routes a sump pump or downspout into a sewer line, ask the City where that water is allowed to go. A good proposal should say exactly where the discharge ends up.

Common waterproofing approaches

Surface fixes: regrading, gutter repairs and downspout extensions. These are often the cheapest place to start.
Crack sealing: injecting a leaking, non-structural crack. See foundation crack repair.
Interior drainage: a drain along the inside of the footing that carries water to a sump pump.
Exterior waterproofing: digging along the wall to apply a membrane and drain at the footing. It is the most disruptive option.

Which one fits depends on where the water enters, so ask the contractor to show you the evidence. More on options: drainage and basement waterproofing.

Water or structure?

Water and wall movement often show up together, but they are different problems. Horizontal cracks, stair-step cracks in block walls or a wall that leans inward point to pressure on the wall, not just a leak. In that case, get the wall looked at before anyone seals it. See bowing basement wall repair and foundation inspection. Freeze-thaw is part of the picture here too: see our guide to Spokane frost depth.

Fix the water before you finish the basement

The City of Spokane's guide sheet SFR-13 says finishing a bedroom or other room in a basement requires a building permit and an electrical permit at a minimum, and that exposed concrete walls in the finished area must be insulated (it lists R-21 under the Washington State Energy Code). Once walls are framed, insulated and covered, leaks are much harder to find. Solve any water problem first.

Permits and hiring

Some foundation and drainage work needs a permit. Ask the contractor whether yours does and who pulls it, and see our guide on foundation repair permits in Spokane. You can check a contractor's Washington registration with the L&I contractor lookup.

Questions to ask

Where exactly is the water coming in, and how do you know?
Have the grading and downspouts been checked first?
Where will the sump pump discharge go?
Is there any sign the wall is moving, and does that change the plan?
What does the warranty cover, and does it transfer to a buyer?

This page summarizes public sources (NOAA climate normals, City of Spokane guide sheets and the Spokane Municipal Code) and is not engineering advice. A contractor or engineer should confirm what your basement needs.

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