Exterior window sills take more water than almost any other wood on a house: rain runs down the glass and sits on them. In the DMV, peeling paint on a sill is often the first sign that the wood underneath has started to rot. Caught early, it's a small repair. Left alone, rot spreads into the window frame and wall framing.
IS IT ROTTED?
- The probe test: press an awl or screwdriver into the wood. Sound wood resists. Rotted wood is soft, and the tip sinks in easily.
- Peeling paint that won't stay put, dark staining, cracks along the grain, or wood that crumbles.
- Check the corners where the sill meets the side casings; that's where water sits and rot starts.
THE OPTIONS
| Repair | When It Works | Typical DMV Cost per Window |
|---|---|---|
| Epoxy consolidant and filler | Small, localized soft spots | $150 – $350 |
| Dutchman patch (new wood spliced in) | Rot confined to one section | $250 – $500 |
| Full sill replacement in wood or PVC | Rot through most of the sill | $350 – $900 |
| Window replacement | Rot extends into the frame or the window is failing | Varies by window |
Add painting, and any trim or interior repairs, to those numbers.
WHY THE SILL ROTS
- Failed paint or caulk letting water into the end grain.
- A sill with too little slope, so water sits instead of running off.
- No drip edge underneath, so water wicks back into the wall.
- Gutters overflowing onto windows below.
PVC or composite sills don't rot and take paint well. When a sill has to be replaced anyway, they're usually worth the small extra cost on south- and west-facing windows that take the worst weather.
PREVENT THE NEXT ONE
Keep paint and caulk intact, especially at sill corners and the joint with the window. Our guide to fixing peeling exterior trim covers the right prep, and our exterior painting cost guide covers whole-house pricing.
RELATED READING
PEELING PAINT ON EXTERIOR TRIM: CAUSES AND THE FIX
Why trim paint peels, how to prep and repaint so it lasts, and when to replace the wood.
EXTERIOR PAINTING COST GUIDE FOR THE DMV (2026)
What exterior painting actually costs in DC, Maryland, and Virginia — by square footage, surface type, and what drives the price up or down.
HOW TO PREP YOUR HOME FOR EXTERIOR PAINTING
Washing, scraping, caulking, priming — the prep steps that determine whether an exterior paint job lasts 4 years or 12.
Planning a project? See our Exterior Painting service page for scope, process and recent work.
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