Over time, wood dries out and shrinks. If you have wooden window frames in an older house, the wood might have shrunk enough to pull away from the caulking that seals in the window panes. Even if you have metal or vinyl windows, caulking snafus can happen, and the caulk itself could be old or misapplied.
Aside from letting the warm air out of your home, old or bad caulk can cause paint to peel and can let moisture into the window frame, which can lead to wood rot.
Recaulking an old window isn’t difficult. You’ll need a caulking gun loaded with the right kind of sealer (ask an employee at your local hardware store for a recommendation), a putty knife, some paper towels or rags that you can pitch afterward and a steady trigger finger.
Source: Cure for the Common Cold Room
Photo via Dean in SF
Step 1: Clear Out Old Caulk.
Use the putty knife to clean out any old caulk from around the window or frame. You want to start with a work surface that’s empty and fairly clean.
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Step 2: Cut the Tip Off the Caulk Tube and Break the Seal Inside.
You should leave a hole just wide enough to fill the gap with caulk. Once you’ve cut a proper-sized hole, push a long nail, a chopstick, a broken wire hanger or one of your neighbor’s thin screwdrivers into the tip until you feel the seal inside pop open.
Photo via Nathan Friedman
Step 3: Apply the Caulk.
Putting steady pressure on the caulk gun’s “trigger,” run a bead of caulk into the gap you’re trying to fill.
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Step 4: Smooth the Seal.
Using a wet finger or a damp rag, push the caulk into the gap and smooth it out into a nice, curved seal.
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Step 5: Clean Quickly.
Clean any extra caulk off your hands, the window, the caulk gun and any tools you intend to return to your neighbor before the caulk dries.
Photo via Rakka