Seattle-Area Homeowners: Top Moisture & Drainage Issues Inspectors See in 2026

In the Seattle area and across the Pacific Northwest, rain is a way of life. That makes moisture and drainage some of the most important things we look at during a home inspection. Here are the top moisture and drainage issues inspectors see in 2026—and what you can do about them.

Crawl space moisture is extremely common. Poor ventilation, missing or damaged vapor barriers, and water pooling under the home lead to high humidity, mold, and rot. Signs include musty odors, visible moisture on joists or subfloor, and efflorescence on foundation walls. Fixes range from improving drainage and grading to adding or repairing vapor barriers and ensuring adequate venting.

Clogged or damaged gutters and downspouts are another frequent finding. When gutters don’t drain, water overflows and runs down siding and next to the foundation. That can cause rot around trim, staining, and basement or crawl space intrusion. Inspectors check for proper slope, secure attachment, and downspouts that direct water well away from the house. Prevention: clean gutters regularly and extend downspouts at least several feet from the foundation.

Rot around trim, windows, and doors often goes hand-in-hand with poor drainage and splash-back from the ground. In our climate, wood that stays wet will decay. Look for soft or discolored wood, peeling paint, and gaps. Addressing grading, splash blocks, and trim maintenance can slow or prevent further damage.

Inside, we look for signs of past or active leaks: staining on ceilings and walls, bubbling paint, and musty smells. Proper flashing at roof-to-wall transitions, well-maintained gutters, and good attic ventilation all help keep moisture out. For Seattle-area homeowners and buyers, a focus on grading, gutters, flashing, and ventilation pays off in the long run.