Types of Caulk and Where to Seal Leaks

Knowing where to caulk and what type of caulk to use can help seal leaks in your home.
By MOTHER EARTH NEWS Editors
October/November 1991
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Because as much as 80 percent of air leakage occurs in areas other than windows and doors, caulking is an absolute winter necessity. In addition to checking windows and doors, be sure to inspect the areas where:

  • the wooden sill of the home meets the foundation
  • dryer vents and fan covers pass through the wall
  • furnace vent stacks meet the exterior
  • any air leaks in the basement might lurk
  • plumbing pipes and telephone wires enter the home
  • any two different outside materials meet
  • the fireplace chimney meets the siding.

As a general rule, caulk where a permanent seal is desired, and weather-strip when doors and windows must be opened.

After determining which areas need attention, it's important to choose the right type of caulk for the job. Before buying or using a particular caulk, read each label carefully for storage and application temperatures. Check the descriptions below, and then refer to the chart to determine the best caulk for the job. While the factors may be of varying concern depending on personal preference (amount of money you're willing to spend, lengths you are willing to go to to find a certain caulk, time you wish to spend redoing the job in a few years), it is important to check the temperature resistance of any caulk if you live in a very cold climate.

Oil-Resin Base. This is often the least expensive. It is not particular durable and tends to shrink and harden. It can be painted. This material is found in most stores. It should not be used for long-term application.

Latex Base. This will bond to most surfaces. It is more durable than resin-based material, and also paintable. Some shrinkage will occur. Adequate, but not the best material available.

Butyl Rubber. This paintable material will bond to most surfaces. It is more durable than the others, but it also shrinks. This is often the best choice for use on masonry surfaces, but not on moving joints or places where two different materials meet.

Polyvinyl Acetate. This will bond to most surfaces and is more durable, but it also shrinks and hardens. This sealant is surpassed by other compounds.

Nitrile Rubber. This bonds well to metal and masonry but not to painted materials. It is durable and paintable, but large amounts of shrinkage are reported. Its primary use is for high moisture areas.

Neoprene Rubber. This will bond to most surfaces and is expensive but durable and paintable. Moderate shrinkage is reported. This is especially good for use in concrete walls and foundations.

Silicone Seal. This will bond to most surfaces except concrete. It is very expensive and very durable but not paintable. Little shrinkage is reported. It remains very flexible. This is an excellent caulk for most jobs.

Polysulfide. This needs a primer to bond to surfaces. It is expensive and very durable and little shrinkage is reported. This is difficult to work with, however, and is toxic until cured. It can dry out in arid climates.

Polyurethane. This will bond to most surfaces. It, too, is expensive, very durable and paintable. Little shrinkage reported.

Hypalon. This requires priming for use on porous materials. It is expensive, very durable, and paintable. Little shrinkage is reported. An excellent caulk, easy to work with but, again, not always readily available.

Now that you've found the correct material for the job, you're on to the easy part, caulking your house for winter. Here's how:

  1. Before installing caulk, remove all loose material and dirt from the crack, or the caulk won't adhere to the surface. When caulking a wide crack (3/8 inch or greater), stuff it to within a fraction of an inch of the surface with a filler material urethane tan oakum a fiberglass batt) and then apply caulking material.
  2. Cut off the tip of the nozzle on the tube at an angle so that it gives you a bead of caulk no wider than you need. Next, pierce the inner seal of the cartridge. If necessary, smooth the newly applied bead of caulk immediately after applying it with a tool like a putty knife, or your fingers. You will soon acquire a technique that allows you to apply the caulk to the crack firmly and smooth it to an acceptable finish in one pass of the caulk gun. Caulk should adhere properly to the surfaces around the crack. Problems of inadequate bonding can be caused by poor cleaning of the crack area, incorrect caulk type, or improper placement.
  3. If the caulk that seals your storm is drying out or missing, caulk the top, sides and bottom of the storm-window frame from the inside (between the sash and storm). Leave the weep holes at the bottom of your storm window unplugged: they allow excess moisture to drain out.

Learn more about the characteristics of the different types of caulk in Caulk Characteristics.

To save even more energy around the house, try these do-it-yourself projects:

Insulating Pipes and Heating Ducts 

Oil Burner Tune Up 

Quick Checks for an Efficient, Winterized Heating System. 

Types of Weatherstripping and How to Weatherstrip Your Home 

Log Home Insulation Saves Energy 


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