Rotten Window Frame Repair in Boston

Frame rot is serious. But it's not always game over.

The window frame is the structural box that holds everything together — the jambs (sides), the head (top), and the sill (bottom). When rot reaches the frame, most contractors recommend full window replacement because the frame is what attaches the window to the wall. We disagree. With proper repair techniques, even significantly rotted frames can be saved as part of our full wood window repair service.

Can I repair a rotted window frame, or do I need a full replacement?

In most Boston-area homes the frame can be repaired. Decay is usually confined to the bottom of the jambs, the sill, and the exterior casing, while the rest of the frame is still sound old-growth wood. We cut out the rotted sections, splice in new wood or rebuild them with structural epoxy, and correct the leak that caused the damage. Full replacement is only the honest answer when more than 60% of the frame is gone or the rough opening behind it is compromised.

How frame rot starts

Frame rot usually starts at the sill (which collects water) and spreads upward into the side jambs. Water can also enter from above if the head casing or flashing fails. Once rot reaches the frame, structural integrity is compromised — windows may stick, racking, or even pull away from the wall.

Signs of frame rot

• Soft or spongy wood in the jambs or head

• Visible gaps between the frame and the surrounding wall

• Window sash that doesn't sit square in the frame

• Drafts even when the window is closed and locked

• Cracked or peeling paint extending beyond the sill

• Water stains on the interior trim

How to tell if your window frames have wood rot

Press a screwdriver into the wood at the bottom corners of the frame, where the jamb meets the sill. Sound wood resists. If the tip sinks in under light pressure or the wood crumbles away, that is dry rot. Check the exterior side as well: paint that blisters or flakes in one spot usually means moisture is trapped behind it. Decaying wooden window frames also change color, turning gray, dark brown, or greenish before they go soft.

Our frame repair process

Step 1: Source identification

Before any repair, we identify why the frame is rotting — usually a flashing failure, missing caulk, or a damaged sill. If we don't fix the source, the rot will return.

Step 2: Damage assessment

We probe the frame to map the full extent of rot — visible damage is often only 20–30% of what's actually there. This gives us an accurate scope.

Step 3: Repair methods

Depending on damage, we use a combination of:

• Wood splicing — replacing rotten sections with new solid wood

• Epoxy reinforcement — for areas where structural strength is needed but wood is partially damaged

• Section replacement — replacing entire jambs or head pieces when too far gone

Step 4: Weatherproofing

We address the original cause of the rot — install proper flashing, caulk seams, and seal the frame against future water intrusion.

How much does rotten window frame repair cost in Boston?

The price depends on how far the rot has spread, and we confirm it on site. Typical ranges:

• One piece of rotten trim or casing replaced in PVC: $145

• Both side casings: $290. Both sides plus the head: $375 to $435

• Rotten sill replaced in PVC, caulked and painted to match: $345

• Sash rot repaired and repainted: $495 to $795

For comparison, replacing the whole window runs $800 to $2,500 per opening. The assessment visit is free for wood, sill, and glass work.

When frame replacement makes sense

If more than 60% of the frame is severely rotted, or if the rough opening itself has structural damage, full window replacement may be the better option. We'll always tell you honestly when repair isn't the right call — no upselling.

Here is what a finished repair looks like: before and after a rotted wood window restored. Once the frame is sound again, weatherstripping keeps drafts and water out for good.

Get a free assessment

Rotting wooden window frames only get worse with time, and more expensive to fix. Call (617) 982-1211 for a free on-site evaluation in Boston, Brookline, Newton, and surrounding towns.