Caulking is a year-round job. In the spring, we caulk the exterior of our home to get it ready for painting. In the summer, we recaulk tubs and showers that may have mildewed during the winter and spring. In the fall, we find ourselves caulking windows and doors and other potential sources of winter air and water leaks. Finally, during the winter, when ceilings tend to drip, we go for our stash of roof-patch/caulk.
There are four basic types of caulking: latex, butyl, silicone and polyurethane.
1. Latex caulk is the most popular because it 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 wallboard and 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 denser and therefore slightly more expensive.
Exterior grade latex can be used inside, but interior grade is not for outdoor use. Latex caulk does not expand and contract and has a tendency to shrink and crack. Latex modified with silicone improves on plain latex with the combination giving some elasticity to the mix.
2. Butyl-rubber caulk works best on concrete, concrete block, brick, stone, gutters, flashings and chimneys. Butyl caulk is special because of its ability to be used under extremely wet conditions. 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 takes forever to dry enough to be painted. Butyl caulk is difficult to work with. It is stringy when applied, requires paint thinner at cleanup time, shrinks a lot and, as we mentioned, is slow drying.
3. Silicone caulk is more expensive than latex and about the same price as butyl caulk. Silicone is great for sealing metal, glass, tile and other smooth, nonporous surfaces.
Of the three mentioned so far, it is the most flexible and shrinks the least. Silicone is especially well suited for sealing dissimilar materials.
Silicone is much like butyl caulk and can be very difficult to deal with, requiring a solvent such as alcohol for cleanup. If you intend to paint over a bead of silicone be sure that you purchase “paintable” silicone.
Most silicone caulks are not paintable. Silicone is not meant to be used on masonry or stone and doesn’t do well on redwood or cedar.
Because acetic acid is the solvent that keeps them damp, silicone caulks have a sharp, irritating smell.
4. Polyurethane caulk is our idea of the ultimate sealant. Our claim is somewhat bold considering the fact that there are so many types of sealants on the market. However, we feel that urethane sealant has taken all the best attributes of all other sealant types and put them it into a convenient, single component cartridge ready to solve your most difficult caulking project.
Urethane caulk can be difficult to apply. It has a sticky, puttylike, consistency and requires mineral spirits for both tooling and cleanup. But it will cure into a paintable rubber capable of stretching more than 300 percent. Some manufactures boast as much as 1,200 percent elongation.
Plus, it has very high tensile strength. It can adhere to almost any type of surface including concrete, wood, glass, plastic and metal. Its incredible ability to adhere to so many dissimilar surfaces is just one of its fantastic features that is important when trying to create a seal between materials that expand or contract at different rates.
On top of everything else, urethane caulk has excellent chemical resistance.
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 of any groove: the bottom and both sides. Each of the three surfaces help to hold the caulking in place. If a crack or groove is deeper than a 1/4 inch, we recommend that you use a foam packing dowel, packing string or packing cloth as a base.
When working with caulk be sure to have the proper solvent on hand to clean up messes and messy caulking lines. Also, an ample supply of paper towels is a must: Start with a full roll for most projects.
For tips from James and Morris Carey, go to www.onthehouse.com or call the listener hotline, 800-737-2474, ext. 59. The Careys are on KRKO (1380-AM) from 6 to 10 a.m. every Saturday.
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