Installation of SPF involves different procedures based on the existing roof structure. It is important to be familiar with all state and local building codes to assure the appropriate materials and procedures meet the necessary requirements in your area.
Roof Surface Preparation
Proper preparation of the substrate, as well as professional application of the foam and elastomeric coating, is certainly the most important process in achieving a successful SPF roofing application. SPF requires a clean, dry surface, free of contaminants, for proper application and adhesion. Often a re-roofing application will involve removal of some, or all, of the existing roof system to provide a clean surface to apply the SPF. Existing SPF systems will need to be cleaned, primed, and recoated every 10-15 years. If the roof has been maintained properly, then a quality SPF roof could last up to 50 years or more.
Once the surface has been properly prepared for SPF application, the "A" and "B" components (isocyanate and polyol resin) are pumped from separate 55 gallon drums, into a specially designed proportioning machine. The materials are heated to a specific process temperature and proportioned to the correct ratio. The two liquid materials are kept separate until they pass through the machine, through the heated hoses and out to gun, where they are finally mixed and sprayed onto the substrate. The SPF is applied to a specific thickness defined by the specification. SPF is typically applied in ½ inch to 1-inch layers, or "passes." Roof specifications or sloping designs that require more foam are applied in multiple passes. The SPF is sprayed down as a liquid, quickly rises in seconds, and can be walked on in minutes.
Spraying foam requires at great deal of training and experience to assure proper mixing of the foam is being achieved while maintaining a high level of productivity and quality of workmanship. Several companies in the industry provide this training to new and intermediate contractors.
Proper weather planning is also a must. Although there are many systems available to meet the various climate conditions, like most other roof systems, SPF cannot be applied onto a wet or damp substrate, or adhesion will be jeopardized and the potential for failure is almost definite. Be sure to check your weather forecast for rain before starting the job.