How often should you re-caulk your windows and doors?

Failed seals let in drafts, water, and waste heating/cooling.

Failed sealant lets wind-driven rain into the wall around the frame, where it rots timber and wets insulation without showing inside until the damage is advanced. The energy loss is smaller but constant, and around a whole house the gaps add up.

1. Inspect on a cold or windy day. Draughts are far easier to feel when there is a temperature difference. Run the back of your hand around each frame.
2. Remove the failed sealant. This is most of the job. Use a sealant removal tool or a sharp knife and take it back to clean substrate. Some products can go over a previous application and others cannot, so check the label, but nothing bonds to a bead that has already let go.
3. Clean and dry the joint. Wipe away residue and dust, using the cleaner the sealant maker recommends. Let it dry completely.
4. Fit backing rod in deep joints. Natural Resources Canada advises a backer rod or foam rope in joints of 6 mm (1/4 inch) and larger before caulking. It sets the depth so the bead can stretch instead of tearing.
5. Mask both sides if you want a clean line. Tape, apply, tool, then pull the tape while the sealant is still wet.
6. Apply in one continuous pass. Keep steady pressure and a consistent bead, pushing the sealant into the joint.
7. Tool the bead immediately. A wet finger or a spatula presses the sealant into contact with both faces. This step is what makes it stick.

• Cracking, shrinking or splitting along the bead
• Sealant that has lost adhesion and lifted from one side
• A draught you can feel at the frame edge on a windy day
• Staining, peeling paint or soft timber below a window
• Daylight visible at the frame perimeter

• Applying new sealant over a bead that has already lost its bond
• Using the wrong sealant: products differ in flexibility, paintability, sun resistance and what they stick to, so read the label for exterior use on your materials
• Filling a deep joint solid with sealant instead of using backing rod, so it tears rather than stretches
• Sealing over rotten timber, which hides the problem while it continues
• Sealing weep holes at the bottom of frames, which are deliberate drainage and must stay clear

• The elevations that take the most sun (south-facing in the northern hemisphere, north-facing in Australia) tend to fail first
• Large temperature swings mean more joint movement and shorter sealant life
• Quality varies: the Natural Resources Canada sealant table lists durability from 5 to 10 years for some caulks up to 20 years or more for others

If the timber beneath is soft, or the frame itself has dropped or racked, sealant is not the repair. That needs a joiner or window specialist.