How to Identify Structural Wood Rot
A Homeowner's Guide for the Pacific Northwest

The location and depth of the rot are key indicators. Structural rot affects load-bearing members like floor joists, rim joists, sill plates, headers, or support posts—not just decorative trim. Use the screwdriver test: if a screwdriver easily penetrates more than 1/4 inch into the wood, it's compromised. Surface rot on trim boards or siding can be cosmetic, but if you see sagging floors, sticking doors, or cracks in drywall, you likely have structural rot causing the building to shift. Always call a professional if rot is found on any load-bearing member.

Dry rot (Serpula lacrymans fungus) has distinct visual signs: orange-brown dust or spores around the affected area, greyish skin or white wool-like mycelium growth on the wood surface, and deep cracks across the grain that make the wood look like alligator skin. You'll also notice a distinct musty, earthy smell in the affected area—often in crawlspaces, attics, or behind walls. The wood becomes brittle and crumbles easily when dry. In Western Washington's damp climate, dry rot spreads rapidly once established, so early detection is critical.

No—structural wood filler and epoxy products are for cosmetic repairs only, not for restoring load-bearing capacity. While epoxy can fill voids and seal against further moisture intrusion, it cannot replace the structural strength of solid wood. For compromised beams or joists, you need sistering (attaching a new member alongside the damaged one), installing wood beam repair plates (steel reinforcement), or complete replacement. Using filler on a structural member is dangerous and violates building codes. At D's Custom Woodworks, we provide honest assessments and only recommend repairs that ensure your home's safety.

Costs vary significantly based on accessibility and the extent of damage. For minor joist sistering in an accessible crawlspace, expect $450-$800 per joist. Rim joist replacement in a basement runs $1,200-$2,500. Sill plate replacement (which requires lifting the house) can range from $3,000-$8,000+ depending on the linear footage. Exterior wall studs are typically $500-$1,200 per section. Our inspections start at $150 and are credited toward repair if you proceed with us. Local labor rates in Mason and Thurston counties and material costs impact final pricing.

Usually not if the rot resulted from lack of maintenance or gradual deterioration. Standard homeowner's policies exclude damage from wear and tear, moisture, or neglect. However, if the rot resulted from a sudden, covered event—like a burst pipe, storm damage, or a roof leak from wind-damaged shingles—it may be covered. Document everything with photos and get a professional inspection report from a licensed contractor. At D's Custom Woodworks, we provide detailed inspection documentation that can support insurance claims when applicable.

The Pacific Northwest's climate is ideal for wood-destroying fungi. We receive 50+ inches of rainfall annually in Shelton and Olympia, creating constant high humidity levels. Wood needs 20%+ moisture content for rot to develop, and PNW homes often exceed this threshold year-round. Poor ventilation in crawlspaces and attics prevents drying cycles, so wood stays wet continuously. Older homes in the South Sound often lack vapor barriers and have inadequate drainage, accelerating rot. Once established, fungi spread through wood via thread-like filaments, jumping from wet to dry wood.

First, eliminate the moisture source—fix leaks, improve drainage, and increase ventilation. Second, remove all affected wood plus a 12-inch safety margin into solid, healthy wood. Fungal filaments can extend beyond visible damage, so cutting back to clean wood is essential. Third, treat the surrounding area with borate-based wood preservatives like Bora-Care, which penetrate deeply and prevent future fungal growth. Finally, install vapor barriers in crawlspaces and ensure proper flashing and drainage around the repaired area. Half-measures don't work—rot must be fully excised or it will return.

Call a licensed contractor immediately if rot is in a foundation sill plate, floor joist, rim joist, support post, or any load-bearing member. If the rotted area is larger than a shoebox, it's beyond DIY repair. If you notice structural movement—sagging floors, sticking doors, or drywall cracks—don't delay. Also call a pro if the rot is in an inaccessible area like inside a wall cavity or under a deck. At D's Custom Woodworks, we provide honest 'repair vs. replace' consultations and never recommend unnecessary work. Your home's structural integrity isn't something to experiment with.