Redmond Crawl Space Repair

King County describes the Sammamish River as running 14 miles through Kenmore, Bothell, Woodinville and Redmond, and says that in Redmond its flooding can affect Northeast 95th Street. Bear Creek’s largest recorded flood, on January 18, 1986, reached 1,550 cubic feet per second at Redmond, which FEMA’s flood insurance study for King County puts at a 40- to 50-year event. King County’s 2016 mapping of potential landslide hazards along its river corridors included the Sammamish River; across all the corridors it studied it mapped 930 deep-seated landslides.

A flood study describes where water goes when a channel overtops, not what happens under a particular house. What it changes is the set of questions worth asking on a low lot near either stream: has surface water ever reached the crawl space during high water, does the soil under the house stay saturated for weeks after a storm, and does a sump, if there is one, run long after the rain has stopped? A pump that runs for days after every storm may be keeping up rather than failing. When a sump pump never rests explains how to tell the difference, and a flooded crawl space covers the first days after water gets in.

This site has not read Redmond’s own critical-area or flood-hazard maps. Before a drain is trenched or a sump discharge is routed on a lot near either stream or on a slope above one, ask the Development Services Center what applies to that parcel.

Redmond’s wetter ground is made of named soils, which helps in reading it. Earlmont silt loam covers 4.7% of the mapped area and is rated somewhat poorly drained; Tukwila muck covers 2.9% and is rated very poorly drained; the thick-surface variant of Snohomish silt loam covers 2.4% and is rated poorly drained. Map units of open water add another 4.2%. Against that, 65.8% of the mapped area is moderately well drained and 14.5% somewhat excessively drained, the latter mostly Everett very gravelly sandy loam and Indianola loamy sand.

The two kinds of ground call for different readings. On the Alderwood units the soil map is a weak guide to a wet crawl space: the moderately well drained class does not capture water that perches above a denser layer, and roof water and grading are the first things to check. On the silt loam and muck units the map is a stronger hint, because the rating itself describes soil that drains slowly. Either way, the survey describes map units, not lots, and the soil under a particular house is found by looking at it.

Only 2.5% of Redmond’s housing predates 1960, and within that is an oddity: 574 units built in 1939 or earlier, against 297 from the 1940s and 1950s together. The 1960s added 2,583 units and the 1970s 5,641; every decade since has added more than 4,500.

For most Redmond houses, then, the crawl space dates from 1980 or later, and the first thing to check is the condition of what was put there when it was built: how much of the original ground cover is still intact and lapped at the seams, whether anything stored or dragged across it has torn it, and whether the vents are still clear. On the few prewar houses the questions are those of any old house: whether ground cover was ever laid at all, and what has happened to the framing over the soil in the decades since. See vapor barrier versus encapsulation for which of the two scopes fits a younger crawl space.

Redmond’s Development Services Center issues building permits. Over-the-counter permits go through the Redmond ePermitting Service (REPS) and plan-reviewed permits through Plan Review Online (PRO). The city issues its own electrical permits as well, and L&I lists Redmond among the cities where it does not. This site has not read which crawl space work Redmond exempts from a building permit, so ask before assuming.

The ZIP code on an address is a weak guide here. 98052 covers 89.8% of Redmond’s land, and 73.4% of 98052 lies inside the city. But 98053, which covers another 8.5% of the city, lies only 5.1% inside it: by land area, almost all of 98053 is outside Redmond, and a 98053 address is more likely to be outside the city than in it. Where an address is in unincorporated King County, the county’s Permitting Division issues building permits, and it lists no exemption for crawl space work.

Drainage work outside the house brings one more rule. Before excavating, Washington law requires the excavator to mark the area and notify utility owners through the one-number locator service at least two and no more than ten full business days before work starts; only an excavation under twelve inches deep, dug on private non-commercial property by the owner or occupier, is exempt. A footing-depth drain trench is not.

The Department of Revenue lists Redmond at 10.4% for October 1 to December 31, 2026, and a part of Redmond outside the regional transit district at 9%, so the rate for a job depends on its address. It applies to the whole contract price, labor and materials together; the cost guide’s ranges exclude it.