How to use expanding foam spray

Written by wendy adams
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How to use expanding foam spray
Insulate your home with expanding foam spray insulation. (construction detail,steel studs image by Greg Pickens from

Heat loss is energy loss and a house that is not correctly insulated creates costly energy bills year-round. Large areas like a vaulted ceiling, bedrooms or basement, can be sprayed with expanding foam insulation to add a flame retardant ring of protection from heat or cooling loss, insects and unwanted outside noise. The expanding polyurethane foam insulation is sprayed under pressure from a hose with a nozzle between wall studs and ceiling joists to seal and insulate the house. Do-it-yourself expanding spray foam insulation kits are available for home use.

Skill level:

Things you need

  • Masking tape
  • Plastic sheeting
  • Spray foam insulation kit
  • Protective suit
  • Goggles
  • Gloves
  • Respirator with filters
  • Foam saw
  • Putty knife

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  1. 1

    Use masking tape to cover electrical boxes and outlets. Cover windows, vents, doors, floors or anything that should be protected from the spray foam insulation with plastic and masking tape.

  2. 2

    Open the spray foam insulation and unpack all parts. Read the manufacturer's directions thoroughly to have a complete understanding of the components and the process of applying the spray foam insulation before starting your project.

  3. 3

    Position the spray gun 18 to 24 inches from the surface to be sprayed. Apply a 1-inch bead of spray foam insulation around the perimeter of the area between the wall studs. Use a side-to-side motion with the spray nozzle, starting at the top of the wall to completely fill the area between the wall studs.

  4. 4

    Allow enough time for the foam to expand before spraying more insulation on the area. Complete a section of the wall and check it for gaps before moving to the next section. Apply more spray foam insulation if necessary to completely seal the section.

  5. 5

    Cut off excess foam that extends beyond the wall studs with a foam saw. Use a putty knife to scrape foam off the surface of the wall studs. Protruding foam will hinder the installation of drywall or sheetrock. The expanding spray foam insulation must be flush with all wall studs and ceiling joists.

Tips and warnings

  • It is much easier to add additional expanding spray foam insulation than it is to cut off the excess. Use care with the amount of expanding insulation you spray to avoid expensive waste.
  • Do not spray foam insulation near a lit cigarette or any open flame. Wear a respirator with a filter while spraying foam insulation to protect your lungs from damage. Cover your eyes with safety goggles and wear protective clothing with rubber gloves.

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