Caulking is a year-round job. In the spring, you caulk the exterior to get it ready for painting. In the summer, you recaulk tubs and showers that mildewed during the winter and spring. In the fall, you find yourself caulking windows and doors and other potential sources of winter air and water leaks. Finally, during the winter when the ceiling begins to drip, you stock up on caulking for the roof.
There are three basic types of caulking: silicone caulk, butyl caulk and latex caulk.
*Silicone caulk: The most expensive of the basic three is silicone caulking. It is best for sealing metal, glass, tile and other smooth, nonporous surfaces. Of the three, it is the most flexible and shrinks the least. Silicone is especially well suited for sealing dissimilar materials.
Be careful. Silicone is not meant to be used on masonry or stone and doesn't do well on redwood or cedar. Most silicone caulks are not paintable, and because acetic acid is the solvent that keeps them damp, silicone caulks have a sharp, irritating smell.
*Butyl-rubber caulk: This group of caulks works best on concrete, concrete block, brick, stone, gutters, flashings and chimneys. What makes butyl caulk special is its ability to be used in extremely wet areas. This makes it great for jobs underground and on the roof. Butyl caulk also works well on aluminum siding.
Although butyl caulk can be painted, it comes in many colors. Unfortunately, it is difficult to work with. It is stringy when applied, requires paint thinner at cleanup time, shrinks a lot and is slow drying.
*Latex caulk: The most popular of the three is latex or acrylic caulking. Latex is water soluble and that makes it easy to use and easy to clean up after.
It is best used on highly porous surfaces like wood. Since latex caulk is used on both inside and outside surfaces, it is available in an interior and an exterior grade. The exterior grade is a bit more dense and therefore slightly more expensive. Exterior grade latex can be used inside, but interior grade is not for outdoor use.
Tips for use
When caulking, remember that the width of the bead will be about 30 percent wider than the diameter of the hole that you cut in the end of the caulking tube. Start with a small hole. Run a test bead on a scrap of wood. Enlarge the hole at the end of the tube with a razor knife, a little at a time, until you get the desired bead width.
It is important that caulking touch on three sides, the bottom and two sides of the groove being caulked. Each surface helps to hold the caulking in place. If a groove is deeper than a quarter of an inch, we recommend that you use a foam backer rod, string, cloth, paper or some other flexible filler as a base.