Caulking & Weatherstripping

As part of your regular maintenance schedule, be sure to check your facility's caulking and weatherstripping. These simple, cost-effective projects can actually save a substantial amount on your heating and cooling bills without requiring outside help.


Air can leak in and out of a building through cracks around doors and windows, joints between different materials, pipe and wire penetrations, and other small gaps and openings. These leaks can increase your heating and cooling bills, reduce the indoor comfort level, and cause moisture vapor damage.

As a general rule, you should caulk any cracks or openings between surfaces, which do not move relative to each other and where a permanent seal is desired.

Indoors or Outdoors?

Most types of caulk can be applied on either the indoors or outdoors. Caulk interior cracks, joints and other openings to help prevent conditioned air from leaking out of the building. In the winter, the heated indoor air contains water vapor, which can condense if allowed to reach a cold surface. The resulting moisture may damage insulation and other materials. Caulk exterior openings or penetrations to prevent moisture from entering the structure and to help "weatherproof".

As a general rule, protect the outside of the building against rain and weather, but allow moisture to escape. Inside surfaces should be made as airtight as possible to prevent conditioned air and water vapor from escaping toward the outside.

Caulking Materials

Caulking compounds come in a variety of types, some for general applications and others for more specialized uses. Elastomeric caulks, including silicone, latex and acrylics will remain flexible over time and are preferred over oil-based caulks. Be sure to check labels carefully to ensure that the type of caulk you select is suitable to your intended application. We recommend using a good grade of siliconized, paintable caulk in most cases.


Step 1

Clean the surface of paint build-up and deteriorated caulk with a screwdriver, putty knife, or wire brush. All surfaces should be clean and dry before application.

Step 2

Cut the tip of the caulk nozzle at a 45-degree angle. It is best to cut the hole a little smaller than you think you will need - you can always enlarge it later. The bead of caulk should be just wide enough to adhere to both sides of the crack or joint. Hold the caulking gun and cartridge at a 45-degree angle, squeeze the trigger slowly, and push or pull the gun and cartridge evenly along the joint.

Note: Fill cracks larger than 1/4" with fiberglass scraps, oakum packing or other suitable materials before sealing with caulk.

Step 3

Use a putty knife or the tip of your finger to tool the caulk into the crack and smooth the exterior surface.

Other Sealing Methods

Caulking materials, which come in rope form, can be pressed into cracks and later removed if desired. This is sometimes used in place of weather-stripping on old, loose windows.

Aerosol foam sealants can be used for sealing larger cracks and openings around pipe and wire penetrations, and at the foundation sill joint. These foams expand to fill the opening and provide a good, tight seal. Be sure to follow the manufacturer's instructions when using this type of product.


Weatherstripping may be used in joints or between surfaces which must be free to move, such as:

  • Where doors meet their frames

  • Where windows meet frames (depending on the type of window, these can include top and bottom sashes, center rails, and side channels)

  • Between swinging glass doors


There are a number of weatherstripping materials varying in cost, durability, ease of installation, and effectiveness. Most are sold either by the foot or in kits for individual doors or windows.

Spring Metal weatherstripping is one of the most effective and durable materials available, but it is more difficult to install than other types and more expensive. It can sometimes improve the operation of older double-hung windows because it provides a smooth surface to slide on.

Plastic or Vinyl V-Type weatherstripping is quite effective and easy to install. It works the same way as the spring metal type, but is less expensive and less durable (lasts approximately three to five years). It comes in rolls with a peel-off adhesive backing, and can be used on the side rails of double-hung windows without interfering with their operation.

Rolled Vinyl or Vinyl Bulb weatherstripping is inexpensive, easy to install, but will wear out after several years. It cannot be used on side rails of double-hung windows, but works well on doors, since it is bulky enough to make up for slight irregularities in fit.

Rolled Vinyl with Aluminum Channel is used primarily on doors. It is more expensive than plain vinyl but lasts longer. It should be installed so that when the door is closed the vinyl is compressed, rather than rubbed.

Adhesive-Backed Foam is one of the least expensive types of weatherstripping available, and the easiest to install; however, it wears out quickly and is not as effective as other types. One of the best places to use adhesive-backed foam is around attic hatches where the amount of wear is minimal.

Foam with Wood Backing is used almost exclusively on doors. It is inexpensive and fairly easy to install, but tends to wear out fairly quickly. The wood backing can be painted to match the door frame.

Door sweeps are used to seal the bottoms of doors where they meet the sill or threshold. They come in several types, including vinyl (least expensive and least durable), vinyl with aluminum backing, and retractable wooden types for use with thick carpeting.

Door Shoes are also used to seal door bottoms, but are attached to the under part of the door and work by being compressed. Many metal doors have this type of seal built in. Door shoes can be effective on any threshold that is not worn in the middle.


There are a great many different types of weatherstripping available and it's important to follow the manufacturer's directions for whichever type you choose.

Double-hung Windows should be weatherstripped where the top and bottom rails meet the sash, where the top and bottom sections meet, and on the side channels where the windows slide up and down. Spring metal and V-type work best. When using the adhesive-back V-type on wood windows, reinforce the adhesive with staples every 6"-8". Rolled vinyl and other compression-type materials can be used at the top and bottom sashes, but not on the side channels, as they will interfere with the operation of the window.

Casement Windows should have weatherstripping applied around all four sides. Spring metal and V-type work well, but if the window is quite loose in the frame, rolled vinyl or other compression types may give a better seal.

Horizontal Sliding Windows should be weatherstripped along the top and bottom channels, where the two sides of the window meet, and where the window closes against the side. Spring metal is preferred because it will stand up to considerable wear from the window sliding across the weatherstripping.

Metal-framed Windows are usually the most difficult to weatherstrip, due to the difficulty of attaching the weatherstripping. The adhesive-backed V-type will usually stick to metal if the surface is first cleaned with rubbing alcohol. Some metal windows have a built-in brush-type weatherstripping which can sometimes be replaced if worn.

Wooden Doors can be weatherstripped with either rolled vinyl, with aluminum channel or foam with wooden backing. Both should be installed so that the foam or vinyl is compressed rather than rubbed. Spring metal or the vinyl V-type also work well if the door is not too loose in the frame. The bottom of the door should be sealed with either a door sweep or door shoe. Severely worn thresholds should be replaced.

Metal Doors usually have a built-in seal, either a compressible gasket or, in the case of sliding or swinging doors, a brush-type weatherstripping. Many of these can be replaced when worn.