Exterior Trim
Exterior Trim Repair: Signs of Rot and When to Replace It
Exterior trim frames the windows, doors, corners, and roofline, and it is usually the first wood on a house to rot. Catching it early keeps a small repair from turning into new sills, casings, or even sheathing. Here is where to look and how to decide between repair and replacement.
Key points
- Rot starts where water sits: window sills, the bottom of door casings and corner boards, and fascia under a clogged gutter.
- Peeling paint, soft spots, gaps at joints, and dark stains are the early signs.
- Small soft spots can be repaired; trim that is soft through or rotting behind the surface should be replaced.
- Replacing trim is the time to fix the flashing behind it, or the rot comes back.
Where trim rots first
Water does the damage, so rot shows up where water collects or soaks in:
- Window sills and the bottom corners of window casings.
- The base of door casings and the threshold area.
- The bottom of corner boards, close to the ground or a roof.
- Fascia and rake boards behind gutters that overflow.
- Any joint where caulk or paint has failed.
How to spot it early
Look for paint that peels or bubbles, dark stains, open joints, and wood that dents when you press it with a screwdriver. Check after a hard rain, when wet wood shows its color, and pay extra attention to the sides of the house that take the weather.
Repair or replace?
A small soft spot on an otherwise solid board can be cut out and patched. When the rot runs through the board, comes back after a repair, or reaches the sill or the sheathing behind, replacement is the better fix. Replacement also gives you the chance to switch to a material that holds up better, like PVC trim.
Fix the water, not just the wood
New trim over the same problem rots again. A proper repair checks the flashing above windows and doors, the drip edge, and the caulk joints, and primes wood trim on every side before it goes up so water cannot wick in from behind.
Frequently asked questions
Can rotted trim just be painted over?
No. Paint hides rot for a season, but the wood keeps breaking down underneath. Soft wood has to be cut out or replaced.
Is it worth replacing trim with PVC?
In spots that stay wet, like sills, the bottom of corner boards, and fascia, PVC is a common upgrade because it does not rot.
Does trim replacement need a permit?
Trim replaced as part of siding, window, or roofing work is covered by that permit. For stand-alone trim work, the town building department decides.
Need exterior trim repaired or replaced?
Cedar House Carpentry handles exterior trim across Cape Cod and the South Shore with our own in-house crew, fully licensed and insured.
See our Exterior Trim work · Find your town · (774) 470-7150