Moisture barriers · Federal Way, WA
Federal Way moisture barriers that cover every inch
The thin plastic laid under Federal Way homes decades ago is usually torn, shifted or missing. We replace it with a continuous, sealed barrier.
- Remove old black plastic buried under fallen batts
- Extra checks on lots near lakes and wetlands
- Seal the barrier at split-level step-down walls
Moisture barriers for Federal Way homes · Kent, WAFederal Way homes
Moisture barriers built around Federal Way houses
Builders in the 1970s and 1980s usually laid a thin sheet of black plastic over the crawl space dirt and moved on. In Federal Way, that plastic has had decades to tear under plumbers' knees, shift away from the foundation walls and get buried under fallen insulation. Wherever the soil is exposed, moisture rises into the floor framing. Homes near Steel Lake, Mirror Lake and the West Hylebos wetlands, or on low lots where the water table rises in winter, feel this most. Signs include a musty smell, condensation on ducts, rusty nails in the subfloor and batts that hang heavy and damp.
A proper barrier is continuous. We clear out the old plastic and debris, rake the soil smooth, and lay heavy polyethylene across the entire floor. Seams overlap and are taped. The sheet runs up the foundation walls and is fastened there, and every pier and post is wrapped so no soil shows. In split-level homes, we pay attention to the step-down wall where the lower floor meets the crawl space, since that transition is often left open. Once the barrier is in, we can reinsulate the floor and seal the vents and gaps rodents use. You get photos of the finished crawl space from end to end.
- Remove old black plastic buried under fallen batts
- Extra checks on lots near lakes and wetlands
- Seal the barrier at split-level step-down walls
- Tape every seam and wrap every pier and post
Local conditions
What Federal Way throws at attics and crawl spaces
The houses
Most of Federal Way was built after 1960, as subdivisions spread out from Pacific Highway and I-5. Marine Hills and the Dash Point area have 1960s and 1970s view homes on sloped lots, often with daylight basements. Twin Lakes, Lakota and Steel Lake are full of 1970s and 1980s split-levels, ramblers and two-stories over crawl spaces, with truss attics and blown-in fiberglass. West Campus adds 1990s and 2000s homes with vaulted ceilings and tighter attic spaces. Many of these houses are now on their first or second set of original insulation and ducts.
The weather
Federal Way sits on a plateau between Puget Sound and the Green River valley, with Poverty Bay and Dash Point on its western edge. The city is dotted with small lakes and wetlands, including Steel Lake, Mirror Lake and the West Hylebos. Tall Douglas firs shade many lots. Rain arrives in long gray stretches from fall through spring, and low spots near lakes and wetlands stay damp for weeks.
The wildlife
Greenbelts, wetlands and wooded ravines run through Federal Way subdivisions, giving rats and mice cover close to houses. Roof rats use fir branches and fence lines to reach rooflines. Norway rats burrow near lakes, creeks and drainage ponds. Squirrels and raccoons from the West Hylebos and the old Weyerhaeuser campus woods regularly test attic vents and roof edges.
Typical results
What moisture barriers looks like
BeforeAfterHow it works
Same crew, same standard, in Federal Way
- 01
Inspect inside and out
- 02
Trace each water source
- 03
Fix the barrier and the vents
- 04
Get roof water away
- 05
Recheck and photos
FAQ
Moisture barriers in Federal Way: FAQ
Still unsure? Call (800) 674-4933 and talk it through with us.
Do I need a moisture barrier if my crawl space looks dry?
Yes. Soil releases moisture as vapor even when the surface looks dry, and in Federal Way that continues through the long wet season. Without a barrier, the vapor rises into the joists and subfloor. A continuous ground cover is required by Washington code for crawl spaces and is one of the simplest protections a house can have.
Is a moisture barrier the same as crawl space encapsulation?
Not quite. A moisture barrier covers the ground and is sealed at seams, walls and piers. Encapsulation goes further, sealing the vents and conditioning the space so it behaves like part of the house. For most Federal Way homes a well-installed barrier is the right starting point. We explain both during the inspection.
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Free moisture barriers inspection in Federal Way.
Book a free inspection. We'll photograph your attic and crawl space and walk you through what we find, before you decide anything.