How to Use Expanding Foam

What is expanding foam?

Expanding foam is a liquefied substance which expands and hardens upon contact with air. It is usually packaged and distributed in canisters and stored under high pressure in order to allow it to maintain its liquefied state until use. It grows greatly in size and must be used in correct amounts to avoid over application. It comes in a number of versions such as waterproof or fire resistant, and other specialty types. The base may be formed from latex, polyurethane and other substances.

Uses of Expanding Foam

Naturally, expanding foam has a number of useful applications. It can be used as insulation due to the expanding volume and its ability to coat a wide area of a surface. Expanding foam also serves as a sealant either for minor repairs such as plugging cracks and holes, or for major household uses such as sealing around windows and doors. This allows it to both seal out unwanted pests such as insects and animals, as well as to assist in insulation by creating a barrier against air seeping between cracks and openings.

Expanding foam is also used as an adhesive since it has binding properties. Many companies also make this variety, which could then be used both as insulation and adhesive, particularly on building or construction projects or home renovations. Specialised fire resistant foam can also be used as a fire suppressant and may be included in fire fighting equipment. The foam is used to seal off the affected area and block oxygen from reaching the fire thereby killing the flames.

How to use expanding foam


  1. Locate all cracks, holes and surfaces to be treated: it is best to do this first so that the canister of foam can be used in a single go since any remaining foam is likely to harden in the can.
  2. Clean surfaces to which foam will be applied: this allows for better adhesion.
  3. Cover other nearby areas, furniture and articles: this will prevent accidental exposure to the expanding foam, which may prove difficult to remove thereafter.


  1. Using gloves, remove the cap/cover and insert the guiding straw into the nozzle.
  2. Shake the can vigorously to ‘wake’ the contents.
  3. Holding away from face, apply foam to the required surface by depressing the spray nozzle.
  4. Apply in an even fashion, preferably in light layers.
  5. Leave to expand and dry for approximately one hour.

Important things to know about Expanding Foam

  • Expanding foam can be purchased in different sizes, so you will need to ensure that the correct size is purchased, as the size of the expanding foam will determine the surface area it will cover.
  • Read labels of expanding foam containers carefully before application.
  • Avoid overuse as the foam once expanded and dried will be difficult to change or remove. Apply additional foam if required and if the surface will be exposed to sunlight, it is recommended that the foam be painted or coated, once it has dried.

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