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Caulk It Up

It seems drafty in my home and some caulk around the windows is dry and hard. Where should I check for areas to caulk and what is the best caulk to use?—Karen H.

If the caulk feels dry and hard, it is probably time to replace it. Even though you may not see cracks and gaps, the caulk is probably not adhering to the window frame or walls.

Wind and temperature changes make a house move quite a bit. The purpose of caulk is to be flexible so it stays attached to the housing materials and continues to stop leakage.

One simple way to find areas that need caulking is to hold the back of your hand near windows and doors on windy days. You will be able to feel serious leaks. Or move a lighted stick of incense around the windows and doors and watch the trail of smoke.

Windows and doors are the most obvious locations for leakage, but they are not always the worst culprits. The sill area, where the walls rest on the foundation, is often the area of greatest leakage.

Check for gaps where the main electrical service, telephone, and cable lines enter your home. Holes for plumbing penetrations for outdoor faucets are often much bigger than the diameter of the water pipe.

Check ceilings around recessed lights, vent fans, ceiling fans, etc. You will probably have to get into your attic and move some of the insulation to check these. While you are there, check for gaps where plumbing vent pipes pass through the attic floor.

There is an overwhelming number of types of specialty caulking, but you should be able to get by with just a few different types.

Also check out the inexpensive caulking tools. Some of these simple tools, for removing the old caulk and for applying a smooth layer of new caulk, can make the job much easier. Since the old caulk is hard and brittle, it was probably not silicone, so a caulk remover (softener) chemical should make it easier to remove the caulk. These chemical removers are not as effective on silicone.

Two main categories of caulking materials are “kitchen and bath” and others. Kitchen and bath caulk has special additives to fight mildew. These will be effective any place there is a high moisture level.

For indoors, where there are not great temperature changes, any latex caulk will be effective. It will have a life of about 20 years or more. It is also paintable. Instead of painting the caulk, kits are available to mix the paint with the latex caulk to tint it for a perfect match.

The most common type of caulk used by homeowners is acrylic latex with silicone added. It costs a dollar or two more per tube than plain acrylic latex, but it lasts about 10 years longer. The addition of silicone makes the caulk more flexible and it adheres better to more materials. It is still paintable and cleans up with soap and water.

Silicone caulk is best used where high flexibility is required, often outdoors. Most silicone is not paintable, so it is available in several colors. It is a bit more difficult to lay a smooth bead with silicone caulk, it has an odor as it cures, and cleanup is more difficult.

For large gaps, expandable urethane foam caulk is a good choice. It also adds insulation value to the gap. It is available in low- and high-expansion formulas. The low-expansion type is better for most applications.

Write for Utility Bills Update No. 937, tips on proper caulking. Include $3.00, a business-size SASE, and Update number. Mail requests and questions to James Dulley, Kentucky Living, 6906 Royalgreen Drive, Cincinnati, OH 45244. Go to to instantly download.

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