Symptoms
- Soft, spongy, or crumbling wood
- Peeling or bubbling paint over the affected boards
- Dark staining or a musty smell near the siding
Likely causes
- CommonFailed paint or caulking letting water into the woodOnce the protective coating cracks, wood absorbs moisture and begins to decay.
- CommonPoor drainage or splashback near the groundSiding too close to soil, mulch, or a downspout stays damp longer than it should.
- PossibleNearby roof, gutter, or flashing leakWater running down from above can concentrate on one section of siding.
- PossibleWood-destroying insects taking advantage of already-soft woodTermites or carpenter ants can move into wood already softened by rot.
What to do
- Press on suspect boards with a screwdriver; if it sinks in easily, the wood is rotted.
- Identify and fix the moisture source, such as regrading soil away from the wall or fixing a leak above.
- Cut out and replace badly rotted boards, cutting back to solid wood.
- Check for insect activity or damage while boards are open, and treat or call a pest professional if found.
- Prime all sides and cut edges of new boards before installing, including the back that faces the wall.
- Caulk seams and joints appropriately, then repaint the full area to match.
- Keep mulch and soil at least 6–8 inches below the bottom of wood siding going forward.
Tools and parts
- Screwdriver (for testing)
- Pry bar
- Saw
- Paintbrush
Replacement wood siding boardsSearch: “cedar or wood siding board”
Exterior wood primerSearch: “exterior wood primer”
When to call a pro
Call a carpenter or siding contractor for extensive rot, and a pest control company if insects are found.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.