Bathroom Window Trim for Moisture — PVC Stool, Jambs and Casing
The wood trim around the bathroom window is peeling and soft, or there is a window in the shower with nothing but drywall around it. We trim it in PVC that can be wet every day.
Bathroom window trim that handles moisture is cellular PVC: a stool sloped toward the room, PVC jamb extensions and casing, joints glued with PVC cement and the window sealed with bathroom silicone. JMB Builders installs PVC window trim in bathrooms and inside showers across the Twin Cities metro, replacing swollen wood or finishing a bare window. Priced per window, quoted from your photos within one business day.
- Priced per window, PVC stool, jambs and casing
- Sloped stool inside a shower
- Quote from photos in 1 business day
- Licensed MN contractor BC809005
A bathroom window lives in steam. The glass is the coldest thing in the room, it sweats every shower, and the water runs down onto the stool. Wood trim there swells at the horns, the paint lifts along the bottom, and the caulk line at the window goes dark. A window inside a shower or over a tub is worse: it gets sprayed directly, and wood or MDF trim there fails in a couple of years no matter how it is painted.
Cellular PVC trim fixes this. It cuts, nails and paints like wood, and water does nothing to it. The stool is the piece that matters most, so inside a shower it is cut with a slope toward the room so water runs off instead of sitting at the window. Jamb extensions and casing are PVC too, joints are glued with PVC cement so they cannot open, fasteners are stainless or coated, and the joint to the window frame gets a bathroom silicone that stays flexible. Painted with a light acrylic or left white, it looks like the trim on every other window in the house.
JMB Builders installs PVC trim on bathroom, shower and tub windows across the Twin Cities metro. We pull the failed wood, check the rough sill and the framing under it, and build the opening back in PVC. On a window in a tiled shower we coordinate the trim with the tile so the PVC jambs and the tile meet in a sealed joint. Painting is quoted as a separate line, or leave it white.
What you supply
- A photo of the window from the room and a close-up of the worst spot, usually the stool ends or the bottom of the casing
- Whether the window is in the shower or tub area or elsewhere in the bathroom
- A photo of the trim on another window in the house if you want the PVC to match its profile
- Your paint color if the PVC is being painted; painting is quoted as a separate line, or leave it white
What JMB supplies
- Cellular PVC stool from thick stock, flat in a dry bathroom or sloped toward the room inside a shower
- PVC jamb extensions ripped to the wall depth and PVC casing in a standard profile
- PVC cement at every joint and stainless or coated fasteners
- Removal of the old wood trim and repair of the rough sill or framing if it is soft
- Bathroom silicone at the window frame and at the tile, paintable sealant at the wall
- Coordination with the tile where the window sits inside a tiled shower
- Photos of the finished window in your job folder
- Painting when you want it done, quoted as its own line
How it is priced: per window
Quoted in writing from your photos within one business day. What moves the number:
- A window inside the shower or tub surround vs. one on a dry wall in the bathroom
- Replacing failed wood trim vs. finishing a new window with nothing on it
- Rot in the rough sill or framing under the old stool
- Stool only vs. the full opening — jambs, casing, stool and apron
- Meeting existing tile, or trimming before new tile goes in
- Matching a specific casing profile in PVC vs. a standard one
- A second bathroom window in the same visit
If the shower is being retiled, tell us the schedule. PVC jambs go in before the tile so the tile can be sealed to them.
How long it takes
A PVC stool and apron on a bathroom window: about two hours. Full PVC trim-out of a window in a shower, including pulling the old wood and repairing the sill: half a day. Painting after the sealant cures.
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
PVC stool and apron only
The casing is fine, the stool is not. The old stool comes out, the rough sill is checked, a PVC stool goes in with horns notched to the existing casing and a PVC apron under it. The quickest fix for the common bathroom window.
Full PVC trim-out
Jamb extensions, casing, stool and apron all in cellular PVC, glued at the joints and sealed to the window. For a bare window in a new bathroom, or a wood trim-out that has failed all the way around.
Window inside a tiled shower
PVC jambs set to the wall depth with a sloped PVC stool, installed before or fitted to the tile, with silicone at every joint between PVC, tile and window. The window itself should be vinyl or fiberglass; a wood window in a shower is a separate conversation.
Solid-surface stool with PVC jambs
A quartz or solid-surface remnant for the stool, matched to the vanity top, with PVC jambs and casing around it. A cleaner look in a finished bathroom, priced with the remnant fabrication.
Bathroom Window Trim for Moisture — PVC Stool, Jambs and Casing: questions, answered
What is the best trim for a bathroom window?
Cellular PVC, sold under names like Azek and others. It cuts and installs like wood, takes paint, and does not absorb water, so it never swells or rots at the stool ends where wood trim always fails in a bathroom. Use thick stock for the stool so it does not look thin, glue the joints with PVC cement, and seal the joint to the window with bathroom silicone. Painted a light color it is indistinguishable from painted wood.
How do you trim a window that is inside the shower?
PVC jambs to the wall depth, a PVC stool sloped toward the room so water runs off, and PVC casing or a tile return at the face. Every joint between the PVC, the tile and the window frame gets a bathroom silicone. If the shower is being retiled, the PVC jambs go in first so the tile is set and sealed to them. The window itself should be vinyl or fiberglass; wood sashes in a shower rot from the inside.
Can PVC trim be painted?
Yes, with a good acrylic paint, and it holds paint well because it does not move with moisture the way wood does. Light colors are the safe choice; dark paint on PVC can make it heat up and move in direct sun, which is rarely a problem on an interior bathroom window but worth knowing. It can also be left white with no paint at all. Painting is its own line on the quote.
Why does the wood trim around my bathroom window keep peeling and swelling?
Condensation runs down the glass after every shower and sits on the stool, and the end grain at the horns soaks it up through the paint. Repainting seals it for a season and then it swells again. Replacing the stool with PVC ends it. Running the exhaust fan during the shower and for a while after keeps the glass drier and helps every surface in the room.
Should the window sill in a shower be sloped?
Yes. A flat stool inside a shower holds water against the window frame. We cut the PVC stool with a fall toward the room so water runs off it onto the tile and down the drain. On a bathroom window outside the shower a flat stool is fine, and it is more useful for setting things on.
Do you need to replace the drywall around the window too?
Sometimes. If the drywall at the bottom of the opening is soft or has mold behind the old stool, that section comes out and is replaced with cement board or moisture-resistant board before the PVC goes on. We see it when the old trim comes off and quote it then, with photos, rather than covering it up.
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 24, 2026 · JMB Builders LLC, MN license BC809005 · All window trim pages
Where we work
Window trim near you
Based in Zimmerman, scheduling across the Twin Cities metro. Closest first: