jbinnall24 October 11, 2011
While taking the order for a recent commercial inspection I was informed that the roofing material was polyurethane. The person who was ordering the inspection from me was no stranger to commercial building, nor am I. I had to ask, are you sure they said poly? The reply was yes. So I said ok and left it at that.
Immediately my mind raced to the application of polyurethane foam to foundations of older homes that I have seen during home inspections, but did not imagine someone would use it on a roof.
Polyurethane roofing has actually been around for some time now and is used as an over-coating option for existing roofs or applied to new roofs as well as to the foundation walls of homes.
It is, simply put, a two part liquid applied under pressure to a surface which expands and forms a seamless coating. Then an elastomeric coating is applied to the top of the foam to keep water out. The coating must be elastic due to expansion and contraction.
I have seen this applied to many foundations in my area while performing a home inspection but this is the first time I have seen it on a roof.
The benefits laid out by the proponents of this are that it is seamless, flexible, light weight and has a good “R” value if the closed cell foam is used. A claimed “R” value of 7.14 per inch of foam.
I don’t want to get the Poly roofing industry on my case here but I have a few issues with this type of application, primarily when used over existing roofs.
First, as you can see in the pic to the left, the top coating can be easily punctured. The material must be applied to a clean and oil free surface. I don’t know too many existing roofs like that.
If a leak does occur, how can we trace it? The coating material does require ongoing maintenance as stated by every company I looked into, and lastly if you had to tear it off…my goodness!
So there you have it. A look at polyurethane roofing from both sides of the coin.