Use caulk to permanently seal air leaks in spots such as the cracks and gaps between exterior window and door frames and your home’s siding. Generally speaking, you can seal openings up to 1/4 inch with caulk alone. For larger gaps, you’ll need to add a backing material before caulking or use a spray foam sealant instead.
Older wood windows may have glass panes that are held in place with putty and glazing points. If the putty is cracked or missing, it is a likely air leakage location and must be re-puttied. (Broken panes should be replaced.) Although caulking may be used to repair/replace window putty, it may be difficult to apply neatly and make future repairs a challenge.
When shopping for caulk, you may be overwhelmed by the choices, so be sure to read the labels on the tubes and choose the caulk that will work best with the materials you’re sealing. Most types of caulk are sold in tubes that fit a caulking gun. In addition, some caulks come in aerosol cans; they’re a good choice for filling gaps up to 1/2 inch. If your budget allows, spend a little more for a higher-quality caulk. The benefit will be a longer-lasting seal; inexpensive caulks may last only a few years, while premium caulks will last much longer. Also note that some caulks are for indoor use only, and that some are paintable—while others are not.
Before caulking, note the following points:
Follow these tips to get a neat, uniform bead of caulking:
Once you have applied the caulk, it takes time for it to dry, or cure. Curing time is described two ways. The tack-free time tells you how quickly the fresh caulk’s outer surface will dry—or skin over. The total cure time indicates the time required for the caulk to become completely stable—or reach the point where no further drying or shrinking will occur.
Most caulks pose no known health hazards after they’re fully cured. However, some high-performance caulking compounds contain irritating or potentially toxic ingredients, and you should apply them only when there is adequate ventilation; carefully read the manufacturer’s instructions and take the appropriate precautions. In addition, make sure pets and people do not come into contact with fresh caulk.
Use expanding foam for large gaps
Expanding foam is ideal for filling larger cracks that caulks can’t handle. It comes in aerosol cans and takes a short time to cure. The foam is very sticky and attaches itself quickly to whatever it touches, so be prepared to pick up any messes fast.
Try these materials for special jobs
In addition to the types of caulk and spray foam sealant described above, you may need to use fillers to plug extra-wide gaps. Fillers come in a wide variety of materials—cotton, fiberglass, foam, and sponge rubber—and you can find them in the caulking department of your local hardware store or home center. However, these fillers are not designed for exposure to the elements; you’ll need to caulk or seal over them.
Steps to caulking
Laying a consistent bead of caulking can take some practice. Follow these steps to provide a good seal: