How to Fix a Drafty Exterior Door
Difficulty: EasyTime: 1–2 hoursUpdated 2026-08-31
If you can see daylight around a closed door, feel cold air at your ankles or watch a candle flame bend in the entry, the seal has failed. Replacing compression weatherstripping, fitting a door sweep, adjusting an adjustable threshold and shimming hinges fixes the large majority of drafts for well under a hundred dollars.
What you’ll need
- Replacement weatherstripping (Q-lon, V-strip or foam tape)
- Door sweep or threshold insert
- Screwdriver and drill
- Utility knife and measuring tape
- Incense stick or a candle for draft testing
Find Where the Air Is Getting In
Close the door and run a lit incense stick slowly along the perimeter on a windy day. Where the smoke pulls sideways, you have a leak. Alternatively, close the door on a strip of paper — if it slides out with no resistance, the seal isn't compressing at that point.
Check all four sides plus the bottom, and also the gap between the door frame and the surrounding wall, where old caulk and dried-out insulation are common culprits.
Replace the Weatherstripping and Sweep
Pull out the old kerf-in weatherstripping and take a piece to the store to match the profile. Cut new lengths slightly long and press them into the groove without stretching, mitring the corners for a continuous seal.
At the bottom, either fit a new door sweep to the door face or replace the vinyl insert in the threshold. Many aluminium thresholds in GTA homes are adjustable — turn the screws in the threshold cap up until it just contacts the sweep.
- The door should close with light resistance, not slam freely.
- Foam tape is fine as a temporary fix but compresses permanently within a season or two.
- Caulk the exterior trim-to-siding joint with a paintable exterior sealant.
- Add insulation in the gap behind the interior casing if it's empty.
When the Door Itself Has Moved
A door that seals at the top but not the bottom, or catches on the latch side, has shifted. Tightening or replacing hinge screws with 75 mm screws that reach the framing pulls a sagging door back into square.
If the slab is warped, the frame is rotted at the base or the brickmould is deteriorating, sealing is a temporary measure — replacement is the real fix.
When to call a pro instead
- A rotted door frame, sill or brickmould
- A warped or delaminating door slab
- Doors that need the frame reset or re-shimmed
- Sliding patio doors with failed rollers or seals
- Full door and frame replacement, including exterior finishing
Tell us the job and we’ll connect you with trusted local pros. Free, no obligation.
Frequently asked questions
- How much heat does a drafty door lose?
- Gaps around a single exterior door can be equivalent to a fist-sized hole in your wall — noticeable on both comfort and heating cost through an Ontario winter.
- Which weatherstripping lasts longest?
- Kerf-in Q-lon and silicone bulb seals outlast foam tape by years and keep their compression through freeze-thaw cycles.
- Why does my door only leak in winter?
- Cold contracts materials and shrinks seals, while the stack effect pulls outside air in at lower levels of the house, making bottom-of-door leaks far more noticeable.