Types of Caulking and Glazing Compounds
Silicone Rubber: lasts 12 to 30 years or more and offers the best adhesion for use in seams, cracks and gaps up to 1/4". It adheres very well to all clean surfaces. Pure silicone does not allow paint to adhere, so impurities are added for adhesion in some formulations. It is available in many colors and clear.
Butyl Rubber: lasts 8 to 10 years, has some shrinkage, and is for use in seams, cracks and gaps up to 1/4". It is available in many colors.
Acrylic Latex: Silicone Blend lasts 12 to 20 years and features easier application than the preceeding rubber caulks. It is intended for use in seams, cracks and gaps up to 1/4". Depending on the manufacturer, it may not take painting.
Acrylic Caulk: lasts 8 to 10 years. It features easy water clean-up and is for use in seams, cracks and gaps up to 1/4". It goes on easily and has no offensive odor. It is available in many colors.
Latex Caulk: lasts 2 to 10 years, features water clean-up, and is intended for use in seams, cracks and gaps without expansion or contraction up to 1/4". Most are paintable. Many are available in colors.
Oil Base Asphalt Caulk: lasts 1 to 4 years. It is dispensed as a soft and tar like compound for use in seams and gaps on the roof around chimneys, stacks and pipes to 1/4". It hardens rapidly in cracks.
Caulking Cord: usually considered a temporary weather-stripping product. It lasts 1 to 2 years, peels from a roll and is then pushed into place. It is usually a temporary filler around storms and air conditioners. It comes in rolls and unused portions can be stored for years.
Oakum: twisted hemp treated with tar. It is cut to the needed length pushed into place. It is used to stuff large gaps before using caulking over the oakum.
Glazing Compound: lasts indefinitely. Application requires some practice with a putty knife, and is used as a seal between the window glass and frame, an often overlooked area needing repair.
Linseed Oil Putty: has basically been replaced by glazing compound in recent years. It is harder to work with, offers less adhesion and cracks faster.
Where to Use Caulking
Unfilled gaps and cracks in the foundation, around windows and doors, in vents, and so on, can let winter cold air and summer heat in exactly as if a window was left open. In fact, a 1/8 inch opening around just two door frames can let in as much cold air as a 12 inch window opened 6 inches all winter long.
Caulking is used around outside window and door frames, and to fill outside wall and foundation cracks. The money you spend on caulking is usually recovered in one heating season or less. This one season "pay-back" period means that money for heating fuel is saved equal to or greater than what you spent for caulking and weather stripping materials.
A clean joint is the first and most important step. Clean away all old caulk, loosen paint or dirt, and apply new caulk to dry surfaces. The easiest and most common way to use caulk is to buy caulking cartridges, for which you will need a caulking gun. A rough estimate is that you will need 1/2 cartridge per window or door, four for the foundation sill, and at least one more for around faucets, vents, pipes, electrical outlets and the like.
Cut off about 1/2 inch of the cartridge tip on a 45 degree angle and puncture the tip seal with a nail. You can use the nail later to act as a stopper for any unused caulk. With a little practice on a joint that's not visible, you'll soon be able to lay a uniform wide bead that overlaps both sides for a good seal. Finish the surface with a moistened finger if you like, but it's not necessary. Remember to use a filler, like oakum, for wide joints before you caulk.
Some but not all the places you should look when surveying you home before caulking are around doors and windows, dryer vents, faucet pipes and wires, where porches attach to the house, seams between masonry and siding, chimneys, and inside corners.
Before applying caulking compound
Clean the area of paint build-up, dirt or deteriorated caulk with solvent and a putty knife or large screwdriver. Drawing a good bead of caulk will take a little practice. First attempts may be a bit messy. Make sure the bead overlaps both sides for a tight seal. A wide bead may be necessary to make sure caulk adheres to both sides. Fill extra wide cracks like those at the sills (where the house meets the foundation) with oakum, glass fiber insulation strips, etc. In places where you can't quite fill the gaps, finish the job with caulk.
This article has been contributed in part by Michigan State University Extension