Window Trim Water Damage Repair — Casing, Stool and Apron Replaced
The paint on the window trim is bubbling, the bottom of the casing has swelled into a lump, and there is a brown line on the apron. The leak is fixed or about to be. Now the trim needs to be replaced, not painted over.
Window trim water damage repair means replacing the casing, stool and apron that swelled, stained or split from a leak or condensation, once the water source is fixed. JMB Builders does it across the Twin Cities metro: we pull the damaged trim, check the jamb and drywall behind it for wet, replace what is soft in primed wood or PVC, prime with stain blocker and caulk at the frame. Priced per window, quoted from photos within one business day.
- Priced per window; casing, stool and apron together
- Trim goes in after the leak is fixed, not before
- Stain-blocking primer so the mark does not bleed back
- Quote from photos in 1 business day
- Licensed MN contractor BC809005
Water gets to window trim from two directions. From outside, through a missing drip cap, a failed sill flashing, a gap in the siding or a window that was never sealed, and it shows up as a stain at the top corners of the casing or a soft spot at the bottom of the legs. From inside, as condensation running off cold glass all winter, and it shows up as a swollen stool, a peeling apron and casing legs that have gone soft where they meet the stool. MDF trim is the worst for it: it drinks water at the end grain and swells into a lump that no amount of sanding fixes.
The order matters. New trim on a window that is still leaking is new trim that will be swollen again by spring. So the first question is where the water came from, and whether that is fixed. Condensation is fixed with humidity and airflow, not carpentry. An outside leak is fixed on the outside: a drip cap, new flashing, new brickmould, caulk where it was missing. We do that exterior work too, or you have someone else do it, and then the interior trim is the last step.
JMB Builders replaces water damaged window trim across the Twin Cities metro. We pull the casing, stool and apron, look at the jamb and the rough sill under the stool and the drywall beside the casing, and replace what is soft. New trim goes in as primed pine or poplar, or cellular PVC on a window that sweats hard every winter, sealed with a stain-blocking primer so the old water mark does not bleed through the new paint. The joint between the stool and the frame is caulked so it sheds water instead of holding it. Painting is quoted as a separate line, or leave it primed and caulked and paint it yourself.
What you supply
- A photo of the whole window and a close-up of the damage: the swollen edge, the stain, the peeling paint
- What you know about the water: a leak that was fixed, a leak that still shows up in rain, or condensation every winter
- Your casing profile, or a photo of another window in the house to match
- Paint or stain color if you want us to finish it; painting is quoted as a separate line, or paint it yourself
What JMB supplies
- Removal of the damaged casing, stool, apron and jamb extensions, and a look at what is behind them
- New trim in primed pine or poplar, or cellular PVC for a window that sweats hard, in a matching profile
- Rough sill or jamb extension replacement when the wood behind the trim is soft
- Drywall patching beside the casing where the water ran into the wall
- Stain-blocking primer on the new trim and on any stained drywall so the mark does not come back
- Caulk at the frame and the stool joint so water runs off instead of soaking in
- Exterior fixes when the leak is from outside: drip cap, flashing, brickmould, quoted as their own line
- Painting or staining of the new trim when you want it done, quoted as its own line
- Photos of the finished window in your job folder
How it is priced: per window
Quoted in writing from your photos within one business day. What moves the number:
- Stool and apron only vs. the full set of casing, stool, apron and jamb extensions
- Whether the rough sill or jamb extensions behind the trim are soft too
- Drywall beside the window that is stained or soft and has to be cut back
- Pine or poplar vs. PVC, and paint-grade vs. stain-grade in a matching species
- Matching an existing casing profile vs. a standard one
- Whether the exterior leak is fixed already or we fix it in the same visit
- How many windows in the same visit; condensation damage is usually on several
Tell us whether the water is a leak or condensation and whether it is fixed. If you are not sure, send a photo of the outside of the window too and we will say what we see.
How long it takes
One window, trim only: half a day. With a rough sill repair and drywall patch: a full day. Several windows with condensation damage: two to four a day. Painting adds drying time.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Condensation damage at the bottom
The stool is swollen, the apron is peeling and the bottom few inches of the casing legs are soft. Everything above is fine. We replace the stool, apron and the lower casing with a scarf joint or the full legs, in PVC where the window sweats every winter.
Leak from outside
Stain at a top corner, a soft head casing or a leg soft its whole length. The water is coming through the wall. We find the entry on the outside, fix the drip cap, flashing or caulk as its own line, then replace the interior trim and patch the drywall.
Swollen MDF trim
MDF casing and aprons swell at any cut end that gets wet and never go back. We replace the swollen pieces in primed pine or poplar in the same profile, and the rest of the room keeps its MDF if it is dry.
Stain-grade trim
Oak, maple or pine trim that went dark from water. Sanding rarely takes the stain out of the grain. We replace the affected pieces in the same species and leave them ready for stain, quoted as its own line, and match the color to the rest of the window.
Window Trim Water Damage Repair — Casing, Stool and Apron Replaced: questions, answered
Can water damaged window trim be repaired or does it have to be replaced?
Swollen MDF and soft pine have to be replaced; there is no putting the fibers back. A stain on solid wood that is still hard can sometimes be sealed with a stain-blocking primer and painted, if the wood is dry all the way through. We check it with a moisture reading when we pull the trim. Most of the time the stool and apron are replaced and the casing is replaced only where it is soft.
Should I fix the leak before replacing the window trim?
Yes, always. New trim on a window that still takes water is swollen again within a season. If the water is condensation, the fix is lowering indoor humidity and getting air moving across the glass, not carpentry. If it is an outside leak, the drip cap, flashing, brickmould or caulk gets fixed on the outside first. We do that exterior work as its own line, or you have it done, and the trim is the last step.
Why is the paint peeling on my window trim every winter?
Condensation. Warm indoor air hits cold glass, water runs down to the stool and soaks into the wood at the joint, and the paint lifts as the wood swells and shrinks. It is worst on older double-pane and single-pane windows and in houses with a humidifier running. The trim can be replaced with PVC at the stool so it stops peeling, but the water will keep coming until the humidity is lower.
Will the water stain come back through the new paint?
Not if the new trim and any stained drywall get a stain-blocking primer first. A water mark on drywall or on old wood bleeds through regular latex paint in a few weeks. We prime everything that was stained with a shellac or oil-based stain blocker before it gets its finish coat, whether we do the painting or you do.
Is there damage behind the trim I cannot see?
Sometimes. Water that swells the casing has usually also run into the drywall beside it and the rough sill under the stool. We open it up, check the framing and the insulation, and show you what is there before the new trim goes on. A soft rough sill is cut back and replaced; wet insulation comes out. If the window frame itself is soft, that is a window replacement, and we tell you so before spending money on trim.
Does homeowners insurance cover water damaged window trim?
It depends on the cause and the policy. Sudden damage from a storm or a burst pipe is usually covered; slow leaks and condensation usually are not. We photograph what we find behind the trim and list the work on the invoice so you have what the adjuster asks for. Whether to file is between you and your agent.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners and for the builders and dealers we sub for. Counts come straight from our job log; no customer names.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 26, 2026 · JMB Builders LLC, MN license BC809005 · All window trim pages
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Based in Zimmerman, scheduling across the Twin Cities metro. Closest first: