What is Foam Sealant?

Lori Kilchermann

Foam sealant is a type of chemical spray that expands when applied to a surface. Foam sealant goes on as a thick and heavy, semi-soft liquid that begins to grow and become stiff as soon as it makes contact with the environment. As the foam sealant cures, it becomes a very light and extremely porous material that has highly-effective insulating properties. When applied into a crack or hole, the foam sealant expands to fill the entire space and prevents any air leakage.

Foam sealant is sprayed from a can and used as insulation.
Foam sealant is sprayed from a can and used as insulation.

In hard-to-reach areas, foam sealant can often be more easily applied than other sealing or insulating materials. Applying only a small amount of material is required as the foam sealant grows to several times its initial size as it cures and dries. Care must be taken when using this product due to its very sticky make-up. The foam can be difficult to remove once it makes contact with another surface. It is most easily trimmed to size once dried using a razor-blade knife.

Foam sealant can be applied over large areas with a spray gun.
Foam sealant can be applied over large areas with a spray gun.

Protective clothing and gloves should be worn when applying foam sealant to any area. The sticky chemical bonds instantly with anything it touches, making clean-up difficult. If contact is made with skin, it is recommended to wash the affected area immediately with a paint thinner or solvent followed with plenty of hot soapy water. Clothing which comes in contact with the foam sealant should be discarded.

Commercial grade sealant can be applied to large areas such as a basement wall or to a ceiling by a professional application team. Often used in large buildings to insulate concrete or steel panels, the foam also has effective sound-deadening properties. For most homeowner use, the sealant is sprayed from a small aerosol can and is used to seal gaps around plumbing as well as air leaks around windows and doors.

In some new construction, household wall electrical outlets are sealed against wind leaks by spraying the socket with the foam. Many plumbing lines are also covered with the foam to eliminate flexing and rattling. Spray sealant has replaced fiber insulation for being the sealant of choice in new window application. The expanding properties of the foam create a much better insulator and eliminate any potential for gaps and leaks. Many times the foam will be applied around the entire perimeter of the window opening and will act as a gasket with the window being placed directly on the foam and then fastened with screws or nails.

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