Exterior window trim replacement cost: rot, PVC and aluminum capping

Replacing rotted exterior trim around one window usually costs about $250 to $1,000 in 2026 when the framing behind it is sound, and $1,000 to $2,800 or more when the rot has reached the sill, the jambs or the wall. For a house with several bad windows, total projects often land between about $900 and $3,500, according to national data from HomeAdvisor and Angi. Where your job lands depends on one thing more than any other: how far the water got before somebody noticed.

Newtown SquareJul 2024

The numbers

Siding contractors and carpenters typically charge $65 to $105 per hour for this work nationally. Second-story windows, windows over porch roofs and windows in stucco or brick take longer.

We price trim work window by window, with a separate unit price for sill and framing repair, because you will not know how deep the rot goes until the trim comes off.

What exterior window trim is

Around the outside of a window you usually have:

• Brickmold or casing: the flat or molded boards around the sides and top.
• Head trim or drip cap: the piece over the top, often with a metal drip edge above it.
• Sill: the sloped piece at the bottom that sheds water away from the wall.
• Apron: a board under the sill on some houses.

On older houses all of these are wood. Newer houses often have PVC, aluminum or vinyl trim built into the window.

Why window trim rots

Window trim rots where water sits. The usual causes:

1. Paint failure. Once the paint cracks, bare wood soaks up water every rain.
2. No head flashing. Without a drip cap over the window, water runs down behind the top trim.
3. Flat or back-sloped sills. Water sits instead of running off.
4. Caulk in the wrong place. Caulking the bottom of the sill to the wall traps water behind it.
5. Gutters and downspouts spilling onto the window below.
6. Leaking windows letting water into the frame from inside the wall.

Fixing the trim without fixing the cause means doing it again.

Your three choices

Replace in PVC

PVC trim, such as AZEK, does not rot, holds paint well and can be cut and shaped like wood. It is our usual choice for replacement exterior trim. It moves with temperature, so joints have to be glued and fastened right. Our AZEK and PVC trim guide explains how we install it.

On the stucco farmhouse in Newtown Square, weathered wood rake trim was replaced in white PVC, including the returns. That is the before photo at the top and the after photo below.

Newtown SquareJul 2024

Wrap in aluminum

Custom-bent aluminum capping is fitted over existing wood trim. It looks clean, never needs paint and costs less than replacing trim. It only works over solid wood. Wrapping rotted wood traps moisture and hides the rot until it reaches the wall. We remove soft wood first and only wrap what is sound.

Rebuild in wood

On historic houses, or where a profile has to match, wood is still the right choice. Use rot-resistant species, prime all six sides before installing, and flash the head. Wood trim needs paint every five to eight years.

When rot goes deeper

Once the trim is off, we check the sill, the jambs and the sheathing with a pick. What we find decides the rest:

• Sound wood behind the trim: new trim, flashing at the head, caulk and paint.
• Soft sill, sound frame: replace the exterior sill, or rebuild it in PVC. See our guide on rotted window sill repair.
• Rot in the jambs or the window frame: the window itself may need to be replaced.
• Rot in the sheathing or studs: cut out and replace the bad wood, then flash and trim.

On a stucco house in Lower Merion, the sills had rotted where water sat against the stucco. We cut them out and fitted new PVC sills and trim, sealed to the stucco with a joint that can move.

Lower Merion TwpSep 2025

Trim and siding together

If you are already planning new siding, do the trim at the same time. The siding has to come off around the window to replace trim properly anyway. On the Broomall house, new window trim went in with the new white lap siding beside the brick chimney.

BroomallMay 2025

If you are not re-siding, trim can still be replaced on its own. It just takes care to work around the existing siding.

How we replace exterior window trim

1. Score the caulk and paint lines and remove the old trim without tearing the siding.
2. Probe the sill, jambs and sheathing for rot.
3. Cut out and replace any soft wood behind the trim.
4. Install head flashing or a drip cap so water sheds over the top.
5. Cut and fit new PVC trim with glued joints and stainless or coated fasteners.
6. Leave the bottom edge of the sill open so water can drain.
7. Caulk only the joints that should be sealed, and paint if needed.

Lead paint on older houses

If your house was built before 1978, the old trim likely has lead paint. Removing it is covered by EPA lead-safe rules. The work must be done by a certified firm with plastic below the work area, careful removal and cleanup. It adds some time and cost and is required by law.

How to make it last

• Keep gutters clean and downspouts pointed away from windows.
• Repaint wood trim before the paint cracks, not after.
• Check the caulk at the head and sides every couple of years.
• Look at the bottom corners of sills each spring, where rot starts.

Permits and contracts

Replacing exterior window trim does not usually need a building permit in Pennsylvania. Historic districts may require review of exterior changes, especially changes in material or profile, so check before you switch wood to PVC on a historic house.

Contracts for home improvement work over $500 must be in writing in Pennsylvania, and you have three business days to cancel after signing.

How to spot window trim rot early

Trim rot is cheap to fix when it is small and expensive when it is not. Walk around the house once a year, in spring, and check:

• The bottom corners of each sill, where the sill meets the side casing. This is where rot starts nearly every time.
• The top of the head trim, where water lands first if there is no drip cap.
• Paint that is bubbling or cracking in a line along a joint.
• Dark stains or green growth on the trim or the siding below.
• Caulk that has pulled away, leaving a gap you can see light or dirt in.

Press a screwdriver gently into anything that looks suspect. If it goes in easily, mark the window and get it looked at before the next winter, when freeze and thaw make rot spread faster.

Choosing color and profile

New PVC trim can be painted almost any color with the right paint, but very dark colors absorb heat and make PVC move more. If you want dark trim, ask about PVC made for dark colors or plan the joints carefully. On older houses, we try to match the profile and width of the original trim, because skinny modern trim looks out of place on a house that had wide casings.

Questions people ask about exterior window trim

Can I replace window trim without replacing the window? Yes, if the window itself is in good shape. Trim is a separate part and is replaced often on its own.

Is PVC trim better than wood? For most exterior trim, yes. It does not rot and holds paint. Wood still makes sense on historic houses or where a profile has to match.

Should I wrap my window trim in aluminum? Only if the wood underneath is solid. Wrapping rot hides it and makes it worse.

How long does trim replacement take? A few windows can be done in a day. A whole house of trim, with sill repair, often takes several days.

Is the estimate free? Yes. We look at every window, probe the sills and give you a price per window with a unit price for any rot repair.

See our exterior trim, fascia and soffit service, the PVC rake trim project in Newtown Square and the rotted window sill repair in Lower Merion.

Ask us to look at your window trim