How to Caulk Properly

Some important tips…

• Get a good quality caulking compound suited to the task — cheap materials are often difficult to apply or not very durable.
• Follow the instructions on the cartridge and note the recommended cleaning product (water or specific solvent).
• While caulking your doors and windows, take the opportunity to install or replace weatherstripping and seals to minimize air leaks as much as possible.
• Remember that a building needs some fresh air intake — if you think your home has issues in this regard, consult a heating system specialist.
• Caulk in dry weather preferably and avoid doing so when the temperature is below 5°C (41°F), as the caulking compound will harden and be difficult to apply.
• Have enough caulking cartridges on hand — a standard cartridge produces a bead 6 mm (1/4 in.) wide and 7.6 m (25 ft.) long.

1. Identify the area to caulk

• Visually inspect the most common sources of air leaks (e.g., electrical outlets, trim, windows, fireplaces, chimneys, access hatches).
• Look for signs of poor sealing (tears, water marks, etc.) — if needed, take a photo of suspicious areas.
• Slowly move a candle or thin sheet of paper around windows and at wall-floor and wall-ceiling junctions. If the flame or paper moves, there is likely an air leak.
• Spider webs are also a good indicator of air leaks because spiders tend to build webs where air circulates.

2. Clean the area to be caulked

• Make sure the area is free of dust, paint chips, and old caulking product.
• If necessary, remove cracked and dried caulking with a retractable blade knife and clean the area thoroughly with a brush.
• Replace damaged wood and re-nail boards if needed.
• Insert filler material such as oakum or foam backer rod into very wide gaps (more than 6 mm or 1/4 in.).

3. Prepare the caulking cartridge

• Cut the tip of the cartridge at an angle with a retractable blade knife.
• Break the protective seal by inserting a wire or long nail into the cartridge.

4. Apply the caulking compound

• Hold the gun at a right angle and follow the crack or joint while gently pressing the trigger.
• If needed, use a disposable stick to push the compound into the gap to fill it completely.
• Make sure the compound covers the crack on both sides; add more with the gun if necessary.
• When you finish applying the compound, do not release the gun trigger abruptly to avoid mess.

5. Smooth the joint

If you're using a water-based or silicone caulking compound, dip your fingers in a bowl of soapy water then run them over the compound to smooth the joint; the soap will prevent the compound from sticking to your fingers.