How to Spray Foam Roofs

Sprayed Polyurethane Foam roofing (SPF) is a method of applying a seamless foam roof membrane in commercial and residential roofing construction. According to the specialist spray foam roofing consultancy, American Polytech, “foam roofing has many advantages over traditional roofing methods.” This includes insulation properties that enable SPF roofing to have a thermal resistance value of 7.14 for every one inch depth of foam, and this out performs all other roof insulation materials currently on the market. SPF roofing is lighter than traditional roofing and offers application flexibility for installations on uneven roofs or over existing roofing material.

Things You'll Need

  • Brush
  • Cloths
  • Detergent
  • Water
  • Roofing spray foam (polyol and isocyanate)
  • Spray foam proportioner
  • Spray foam gun
  • Spray foam hosing
  • Full face respirator
  • Rubber gloves
  • Protective suit
  • Measuring tape
  • Elastomeric top coating
  • Elastomeric spray gun or roller
Roof spray foam can go over traditional roofs without removing the tiles.
Roof spray foam can go over traditional roofs without removing the tiles.

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Step 1

Check that the spray foam roofing system conforms to fire safety regulations and tests to a Class A rating by ASTM E-108. Check with state authorities that the roofing system conforms to all building regulations and requirements. Check with building regulators for the minimum depth requirements for spray foam roofing.

Make sure the spray foam roof product tests at a Class A fire and safety rating.
Make sure the spray foam roof product tests at a Class A fire and safety rating.

Step 2

Use a brush and sweep all debris, moss, aggregate and accumulated dirt from the roof. It is important that no loose material is on the roof that prevents the foam from adhering to the surface and providing a water tight membrane. Take time to prepare the roof as this prevents the formation of foam blisters that need repairing after the application.

Spray foam roofing needs a clean surface to adhere effectively.
Spray foam roofing needs a clean surface to adhere effectively.

Step 3

Clean any grease or oil marks off the roof with a cloth using detergent and water. Oil and grease marks prevent a tight seal for the spray foam and cause blistering. Allow all wet areas to dry out completely before applying the spray foam roofing.

Remove grease and oil before applying spray foam roofing.
Remove grease and oil before applying spray foam roofing.

Step 4

Check the connections on the spray foam equipment. The spray foam proportioner pumps solution into the hosing and up to the spray gun, so make sure all connections are tight and leak-free. Add the polyol and isocyanate components that form the spray foam compound to the proportioner as the manufacturer directs.

Check all hosing connections before spraying roof foam.
Check all hosing connections before spraying roof foam.

Step 5

Wear a full face respirator, rubber gloves and a protective suit. Use the spray gun and apply the spray foam evenly over the roof to a minimum one pass depth of 1/2-inch. Use a measuring tape at the edges for accuracy.

Step 6

Allow the membrane to dry for 15 minutes before applying a second pass. Build up the level to the requirements of the base membrane it attaches to, commonly this is at least one and half inches, and comply with building regulations for the minimum depth requirement.

Wait 15 minutes before applying a second coat of spray foam roofing.
Wait 15 minutes before applying a second coat of spray foam roofing.

Step 7

Check that the surface of the spray foam is smooth when it is dry. If it looks like the texture of orange peel or popcorn, it needs another coat.

Orange peel textures need further coats of spray foam.
Orange peel textures need further coats of spray foam.

Step 8

Apply an elastomeric top coat to the spray foam roof in dry conditions. This protects the foam from weather damage and UV-rays. Use a spray gun or roller on the top coat depending upon which product you buy.

Use a flexible elastomeric top coat over spray foam roofing to protect it from UV-rays.
Use a flexible elastomeric top coat over spray foam roofing to protect it from UV-rays.

References

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