Window Sill Replacement and Frame Repair Services
Water getting in is window leak repair; this page fixes the wood the water has already ruined. If your sill rot is part of a whole frame gone soft, compare the cost with full-frame replacement on the homepage.
Rotted Wood Sill Replacement
The exterior sill is the horizontal piece under the window that sheds water off the wall. The National Park Service notes that decay in neglected windows usually starts on horizontal surfaces and at joints where water collects, and the sill is the biggest horizontal surface a window has. The test is simple: push a screwdriver or awl into the wood. The Park Service also notes that a sill can look sound on top while the core underneath has decayed, and that a probe will go straight through that skin.
Replacement means cutting the old sill out, often in pieces, and fitting a new one with the right slope. The new sill should slope down and away from the house, and the Park Service suggests a drip line cut along the underside so water drops off instead of creeping back. The residential code also calls for flashing under and at the ends of sills. HomeGuide prices a typical 3- to 8-foot sill at $250 to $800, and notes that most replacement windows don't come with a new sill.
Jamb and Brickmould Rot Repair
The Park Service lists the joints between the sill and the jambs among the places where decay starts. The bottom of the side jambs and the brickmould (the exterior casing against the brick) sit in the same splash zone. HomeGuide puts wood window frame repair at $120 to $350 nationally to patch or reframe, and frame repair in general at $150 to $600. Rotted sections get cut back to sound wood and replaced with new pieces joined to the old.
If your brickmould is wrapped in aluminum capping, a leaking capping joint can hold water against the wood, and you may not see the rot until you press on it. See window capping for re-cladding once the wood is fixed.
Epoxy Consolidant and Spliced-In Repairs
Not every soft sill needs to come out. The National Park Service describes consolidating decayed wood with semi-rigid epoxies that soak into the porous wood and harden, then rebuilding the surface with an epoxy patching compound that can be sanded and painted. That works well on a sill with shallow decay along its nose or at a joint.
When a section is too far gone for epoxy, the next step is a splice: cutting out the bad section and fitting a new piece of matching profile, sometimes called a dutchman. The Park Service notes these splices take more skill and cost more than consolidation, but they keep the original sill in place. On a house you care about the look of, that's often worth it.
Interior Stool and Apron Replacement
The interior sill, called the stool, is the ledge you set plants on, and the apron is the trim board under it. Condensation running off cold glass lands on the stool, and over a few winters the finish can peel and the ends go dark. HomeGuide lists interior sill materials from vinyl at $5 to $20 per linear foot to stone at $20 to $80, with wood at $7 to $40. A stone or solid-surface stool under a window that sweats every winter is a sensible upgrade; fix the humidity too, or the new one will stain the same way.
Rot-Resistant Replacement Sills
A new exterior sill doesn't have to be wood. HomeGuide notes that vinyl and composite sills resist moisture and rot and fiberglass resists moisture damage, at $5 to $25 per linear foot for the material. On a painted house we lean toward PVC or composite, since the sill is where the water sits. If you'd rather keep wood, ask for it primed on every face before it goes in. Wrapping the sill in aluminum is a separate job on the capping page.
Why Troy homeowners call Troy Windows
- Free in-home measure of every opening
- Written, itemized quote before any work
- Frames and sills checked before a price
- One local window installer, not a call list
- No charge to homeowners for the referral
Window Sill Replacement Cost in Troy
National figures from HomeGuide (September 2025 sill guide; 2023 frame repair guide):
| Job | National range |
|---|---|
| Sill replacement, 3 to 8 ft | $250 to $800 |
| Sill repair, partial | $150 to $350 |
| Wood frame repair or reframe | $120 to $350 |
| Window frame repair, general | $150 to $600 |
| Wood sill material, per linear foot | $7 to $40 |
| Composite sill material, per linear foot | $10 to $25 |
HomeGuide puts labor at 80% to 90% of a sill job, so access and how much trim comes off matter more than the material.
Sill Repair in Older Troy Homes
Lead paint. Sills are friction surfaces, and EPA names them as a common source of lead dust in older homes. Cutting out a painted sill in a pre-1978 house can cross the rule's small-job threshold, so ask for the firm's RRP certificate and how they contain the dust (lead-safe window replacement explains the rule).
Snow and meltwater. The NWS 1991-2020 snowfall normal for Detroit, the nearest station with one, is about 45 inches a year. Snow piled on a sill melts against the wood on sunny days and refreezes at night. Keeping the sill's paint intact, and the caulk joint at the jamb sound, does more than any product.
Repair or replace the window. If more than one corner of the frame is soft, the window is probably due. Sill and jamb repair on a window you'll replace in two years is money spent twice.