I am in the central valley of California. I have coated many flat mineral capsheet roofs with a reflective elastomeric coating here in my area.
In December 2004, I went to Yuma, AZ. and coated the flat roof of an adobe style house. In pressure washing prior to the application, I would guess around 3 double handfuls of granules had come loose and gathered near the roof drain during the cleaning. This amount was what I expected to see and the same amount for a 700 sq ft roof here in the central valley of Cal. This roof was 1 1/2 years old.
In October of this year I went back to Yuma and coated the roof of the house next door to the first one. The houses are the same except the one this time was 150 sq ft larger. This one was a very different story than the first. They were both built at the same time.
The house had developed several roof leaks last winter and had to be repaired. Every seam where the capsheet touched the stucco facade had been re-sealed. There were also large patches, (about 2' x2') in 2 locations.
Here is the kicker to this story. There were large piles of granules loose and blown into corners and a few other areas. So many more granules came loose during the pressure washing I had to get a broom and shovel to remove them before I could finish with the pressure washing. I would estimate enough granules were already loose or came loose during the washing to fill a 2-gallon pail. This was a surprising amount of decomposition in one year's time, using the roof next door as a baseline for the estimate of granule loss.
I contacted the developer that built the homes and they sent a foreman out to see what I was going to do. He said their group had built a few hundred of the adobe style homes but were no longer building them because of warranty call backs, roof and stucco repairs. Everything on and in the new homes had a 3-year warranty and the roof leaks and stucco cracks were costing them alot and giving their company a bit of a black eye.
The roof that was coated last December looked exactly like it did the day it was done, had developed no leaks last winter and the owner said his electric bill had dropped an estimated 35% since it was done.
These are the first roofs I have coated outside of my area. Is the decomposition problem like this on every flat roof in high temperature areas?
The flat roofs there are not lasting 2-years! I expected it would be little worse than my area but I had no idea it would be that bad.
Antone have experience with flat roofs in desert areas? Is this the norm or did I have a faulty roof? With what the foreman said, I expect this is the norm in that area.