Spray foam and coating applications are becoming hotter topics in the commercial roofing industry. With these types of roofing applications, a spray foam insulation or coating is typically applied over an existing roof system. These roof systems are marketed on the concept(s) of lower disposal costs, higher insulation values and long-term roofing warranties for less cost. It should be noted that there are a myriad of spray foam and roof coating applications and that there are coating systems which do not utilize spray foam insulation.

There is no question that the concept of coating over an existing commercial roof for lower cost and less landfill space has appeal in the present market place. At question, is the track record of these types of systems. It is our opinion that a spray foam system is not a stand-alone commercial roof application on low-slope substrates. Nearly all spray foam roof assemblies occur over a pre-existing roof. In lieu of this reality, leakage will only occur when water finds its way not only through the newer foam application, but also through a deficiency in the pre-existing roof.

We have seen spray foam applications which are 15 – 20 years old, and we have seen many spray foam applications which falter within the first five years. Once foam does fail, a complete re-roof down to the deck is generally required, because it is very difficult to know where the point of water entry is with a spray foam system. There is certainly an all or nothing risk factor with spray foam applications, especially when the existing roof is not prepared properly before the spray foam is applied.

Applying a liquid-spray coating over an existing flat roof is a relatively new development in the commercial roofing industry. These systems generally utilize a preparation process and then a two-part coating. Many roofing contractors are trying to understand these systems better in lieu of their potential appeal in certain situations.

It is our opinion that the risk of failure is too high with spray foam applications, and we have been reluctant to promote them.

With liquid coatings, we are taking a wait and see approach with these roofing systems. While these applications definitely save labor, the material and preparation costs can be equal to a typical single-ply roof application. Should the cost of these systems continue to recede however, it will be very tempting to recommend them in the market place, even though their track record is still unproven. Lastly, it should be noted that coatings can be a viable roofing option on sloped metal roofs.