“Foam” is a closed cell plastic insulation spray applied to a minimum thickness of one inch.  It is usually sprayed in only one to two inches thick, primarily because of the cost.  There are two important factors to take into consideration about these roof systems.  One, the foam by itself is not waterproof and with limited exposure, the foam is damaged by the ultraviolet(UV) rays of the sun.  The waterproofing is a liquid coating applied over the foam.  These coatings are made of acrylic, urethane rubber, silicone, or other products.  The absolute minimum thickness of the coating is 25-30 dry mils.

Uses:

This system is often used to “Foam Slope” onto an existing structure and to help move ponded water to drains or scuppers.  It also has very good insulating qualities at over 6.5 per inch.  If used on poorly insulated structures it can substantially reduce energy consumption.

Approximate Life Span:

Given that foam is inorganic, its life expectancy should be indefinite provided it is kept “properly coated.”  You can expect about 20 years for maximum life expectancy if new coating is applied every 5-7 years.

Caution:

• Foam should not be used on roof areas that have heavy foot traffic.  For example, roofs with a lot of mechanical equipment, unless fortified for that purpose.
• Never spray foam over a wet roof.  Be careful, because most roofs that leak show internal moisture content.

Limitations:

• Ponded water will destroy the coating over the roofing material in a short period of time.  Water ponds on the roof must be corrected.
• No less than 25-30 mils of waterproof coating should be installed, depending upon the type of coating.  This is a NRCA minimum.