Ask what it costs to fix wood rot around a window and the answers run from “a few dollars of epoxy” to “several thousand dollars,” and both are true. The number depends on how far the rot has traveled: the surface of the sill, the sill itself, the frame around it, or the wall behind it. Each step outward changes who should do the job and what it costs.
This guide sorts the cost question by how far the rot goes, then compares the DIY epoxy route with a pro using published cost data. The sources are HomeAdvisor’s window sill cost page (updated June 19, 2026), a Toronto-area window company’s repair-versus-replace guide, and a Los Angeles painting contractor’s dry rot pricing page. They do not agree with each other, and the post shows where.
The short answer: cost follows the rot, not the window
| How far the rot goes | Realistic route | What the sources put on it |
|---|---|---|
| Soft paint and a spongy surface layer, solid wood underneath | DIY epoxy repair | Toronto company: about $60 to $120 per sill in materials (consolidant and filler kit, primer and paint) |
| Rot in part of the sill, under about 20 percent of it | Epoxy repair, DIY or a carpenter | Toronto company: $150 to $400 per sill from a pro. HomeAdvisor: $200 to $300 for minor damage repair |
| Most of the sill, or the screwdriver sinks in along its full length | Replace the sill | HomeAdvisor: $150 to $700, average $400, installed cost $75 to $100 per linear foot |
| Rot into the frame or the wall framing behind it | Carpenter, sometimes a contractor | HomeAdvisor: budget another $150 to $1,100 per sill for frame repairs. LA contractor: $2,000 to $4,000 once the damage is structural |
Prices are for 2025 and 2026 and vary by region. The Toronto company’s page uses a bare dollar sign with no currency label, and its figures are most likely Canadian dollars.
Why the same repair gets very different quotes
HomeAdvisor puts a typical sill replacement at $150 to $700 with an average of $400, and says labor is 80 to 90 percent of the bill. It also says repair companies typically charge a trip fee and a minimum of $100 per sill. A Los Angeles painting contractor, ALLBRiGHT, says minor non-structural rot repairs run $500 to $1,000 per repair, and adds that a general contractor managing the job charges 13 to 22 percent on top.
These are not contradictory. HomeAdvisor is pricing one sill. The painting contractor is pricing a repair job in a high-cost metro with the contractor’s overhead built in, and it does not say how many windows or how much wood. When two quotes differ by a factor of three, check what each one covers before you compare the totals.
- Scope. Sill only, or sill plus frame, and whether anyone looked behind the trim.
- Finish. Whether priming and two coats of paint are in the number.
- Minimums. A $100 minimum per sill makes one small repair look expensive. Bundling several windows into one visit spreads that fixed cost.
- The cause. Whether the quote includes fixing the water source (failed caulk, missing drip edge, clogged gutter) or only the damaged wood.
Step 1: measure the rot with a probe, not by eye
Paint can hide how deep rot goes, and it can also make sound wood look bad. The Toronto company’s guide uses a screwdriver or nail pushed into the middle of the sill with light thumb pressure, and sorts the result three ways:
- Sinks in easily: structural rot, so epoxy is no longer enough.
- Resists but feels soft: epoxy may save it.
- Solid: the problem is the paint, not rot.
The same guide gives two rules of thumb for repair versus replace. Under about 20 percent of the sill affected, with sound wood underneath, epoxy is the shallow-rot fix. Over that, or if the probe sinks in along the full length, replace the sill. If the damaged area is larger than a fist, move up to new wood or a PVC sill. That is one company’s rule of thumb, and it sells replacement work, so treat it as a starting point and not a code requirement.
If you do go the epoxy route, the full rotten wood epoxy guide covers the moisture target, the soak-then-fill method and the depth limits from the West System instruction sheet.
A worked example: one 3-foot sill
Take a standard window with a 36 inch sill, and say the rot is a soft strip 12 inches long and 4 inches wide at one end, 48 square inches of surface, with solid wood probing underneath.
- Replace it with a pro. HomeAdvisor’s installed cost of $75 to $100 per linear foot gives $225 to $300 for 3 feet. The Toronto company prices a standard 3-foot wood sill at $250 to $450 in its market. Those two ranges overlap, which is reassuring.
- Epoxy repair with a pro. The Toronto company quotes $150 to $400 per sill, and HomeAdvisor lists $200 to $300 for minor damage repair. On a 3-foot sill that is not much cheaper than replacement, because both prices are mostly labor.
- Epoxy repair yourself. The Toronto company puts materials at $60 to $120 per sill: a consolidant and filler kit at $40 to $90 and primer and paint at $15 to $30. The penetrating step uses little epoxy. The West System sheet says 100 mL of mixed epoxy covers at least 320 square cm, about 50 square inches, so 48 square inches is roughly one batch of 100 mL, well under that sheet’s 300 mL batch limit. A 24 ounce two-part kit is more than one such job, which is why the leftover goes to the next window.
The honest comparison is not purchase price. It is cost per year of service. The Toronto company says an epoxy repair lasts 5 to 8 years and a new wood sill 15 to 25 years. Those lifespans come from a company that sells replacement work, so they lean toward replacement, but they are the only published figures I found. Dividing the prices above by those lifespans:
| Option | Cost | Lifespan | Roughly per year |
|---|---|---|---|
| DIY epoxy repair (materials) | $60 to $120 | 5 to 8 years | $8 to $24 |
| Pro epoxy repair | $150 to $400 | 5 to 8 years | $19 to $80 |
| Pro new wood sill | $250 to $450 | 15 to 25 years | $10 to $30 |
Read that as a pattern, not a promise. DIY is cheapest per year if you value your own time at zero. Paying a pro for an epoxy repair is the weakest value of the three, because you pay the labor-heavy price and get the shorter lifespan. If you are going to pay for labor, new wood buys the most years per dollar.
Where DIY stops being worth it
HomeAdvisor says a DIY sill replacement can save up to 90 percent of the total, about $360 per window, and still recommends a specialist, because a badly installed sill can leak. The Toronto company lists situations to hand to a professional:
- The rot has spread into the window frame or the wall framing.
- Your finger, and not just a nail, sinks into the wood.
- The window no longer closes or locks.
- It is a bay window or a sill wider than about 6 feet.
The LA painting contractor makes the same split from the other side: a small, isolated, non-structural patch, such as a piece of window trim, can be a DIY job, but rot in structural wood is a job for a professional, and a DIY repair that misses the fungus lets the rot keep spreading.
The step that decides whether you pay twice
Epoxy does not kill rot, and a repaired sill that keeps getting wet will rot again, which is the cost nobody quotes. The Toronto guide lists the cheap prevention steps: repaint bubbling paint before storm season, clear the drip edge under the sill with a utility knife, clean the weep holes so water can drain, and reseal gaps with silicone. For the window joint itself, the exterior window caulk guide compares silicone, siliconized latex and polyurethane against the manufacturer data sheets.
One detail where sources disagree: the Toronto guide says latex primer over cured epoxy tends to peel, and recommends an oil-based primer. West System’s sheet says epoxy works with most varnishes, polyurethanes and paints, so the safest move is a small test panel with your own primer and paint.
Two kits the repair sources point to
Abatron Wood Restoration Kit (LiquidWood and WoodEpox, 24 oz). A two-product system: a penetrating consolidant and a hand-moldable filler. It covers both jobs in one box: soaking the soft wood and then rebuilding a missing corner. In stock when checked, sold by AD Distribution, 4.5 stars from about 1,400 ratings with 5 percent at one star. Reviewers like it for filling rot voids and for sanding and painting, and some find it slow to dry.
Check price on Amazon: Abatron Wood Restoration Kit. This is an affiliate link (see our disclosure for details).
System Three RotFix (24 oz kit). A penetrating sealer and consolidant sold with a putty for the rebuilding step. The data sheet gives a 45 degree F minimum application temperature, and it says plainly that the product does not kill rot fungus. In stock when checked, sold by System Three Resins, 4.5 stars from about 350 ratings, 3 percent at one star.
Check price on Amazon: System Three RotFix. This is an affiliate link (see our disclosure for details).
Questions to ask before you accept a quote
- Did you probe the wood, and how far does the rot go: sill only, frame, or behind the trim?
- Is the water source part of the job, and what happens if it comes back?
- Is paint included, and is the primer compatible with epoxy if epoxy is the method?
- Is there a trip fee or a per-sill minimum, and is the price lower if you bundle several windows?
- Is the repair guaranteed, and for how long?
Quick rules
- Cost follows how far the rot has traveled, so probe first.
- Under about 20 percent of the sill with solid wood underneath: epoxy is a sensible repair.
- Paying a pro for an epoxy repair is the weakest value on the cost-per-year math; DIY epoxy or a new sill beat it.
- Rot into the frame or wall framing is not a DIY epoxy job.
- Fix the water first or you will pay again.
If the damage is a crack or dent and not rot, the wood filler guide covers the three filler types, and the wood hardener guide covers the thinner consolidants. To choose between epoxy and other adhesives, see construction adhesive vs epoxy vs silicone.
Etienne Basson maintains and repairs his own home, and writes practical guides on choosing the right materials and products for repair and finishing jobs: fillers, sealants, adhesives, and similar. He focuses on what actually works for a specific job, not just a spec sheet.