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Windows · Seal the opening

Drafts at the frame rather than the sash

Air leaking around the frame means the rough opening was never sealed properly. That is fixable without replacing the window.

Quick answerEvery window sits in a framed opening that’s a little larger than the window. That gap is supposed to be sealed. If air pours in around the trim rather than where the sash meets the frame, the gap was left open or the sealant has failed. Pull the interior trim, seal the gap with a low-expansion foam or backer rod and sealant, and reinstall the trim. The window itself is fine.

Where the draft comes from decides the fix. A leaky sash needs weatherstripping or adjustment. A leaky frame needs the opening sealed. Neither one needs a new window.

1Why the frame leaks

  • The gap was never sealed. Older installs often stuffed the gap loosely, or left it empty.
  • Sealant has failed. Caulk at the exterior trim shrinks and cracks over time.
  • A rushed replacement. An insert window set into an old frame without sealing between the two.

2How to check what you’re dealing with

  1. Find the leakOn a windy or cold day, move the back of your hand or a lit incense stick around the trim, then around the sash. Note where the air moves.
  2. Check the interior trimGaps between the trim and the wall, or between the trim and the frame, point to an unsealed opening.
  3. Check the exteriorLook at the caulk where the window trim meets the siding. Cracked or missing caulk lets in air and water.
  4. Look for waterStains below the window mean the opening is leaking water as well as air. That needs flashing, not just foam.

3Fixing it

Do it yourself

  • Caulk gaps between interior trim and wall
  • Remove interior trim and fill the gap with low-expansion foam made for windows
  • Use backer rod and sealant for narrow gaps
  • Renew exterior caulk at the trim

Hire a pro

  • Water stains or rot show around the opening
  • Flashing is missing at the head or sill
  • Many windows leak and you want them all sealed at once
  • Upper-story windows
Use the right foam and work lead-safe

High-expansion foam can bow the frame and jam the sash. Use foam labeled for windows and doors. In a pre-1978 home, removing painted trim can release lead dust; paid work should be done by a lead-safe certified firm.

4What drives the cost

The number of windows, whether trim can be removed and reused, height, and whether flashing or rot repair is needed. Sealing an opening costs much less than replacing a window.

Windows cost

Drafts and water stains around the frame?

Talk to a window contractor who will seal and flash the opening.

877-360-4657

5Questions

Will new windows fix the draft?

Only if the new opening is sealed properly. Seal the existing opening first; it’s the actual problem.

How do I tell a frame draft from a sash draft?

Test with your hand or incense. Air at the trim and wall is the frame. Air where the sash meets the frame is the sash.

Can I just caulk the outside?

Exterior caulk helps with water. The main air seal belongs on the inside, between the window and the rough opening.

Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.

877-360-4657