I had decided on covering my flat roof (68 sqrs) with the Durolast membrane. Part of the attraction was that I could cover over my old SPF foam roof quick and easy.
The contractor and sales rep dangled this cover method as a way to get the job while minimising most talk of old roof and wood replacement. As the crew started, it became quickly obvious that the wood decking was all rotted out and therefore was a total tearoff.
During the tearoff, A layer of lightcrete was removed which was meant to provide a slight slope, though I didnt know that at the time. The contractor said the purpose of the lightcrete must have been to provide rigidity. When we got down to joists and structure, we noticed that many of old joists sagged in the middle.
Only rotted out joists were replaced and the sags ignored. Decking was nailed down, and two layers of inch and one half ISO board layed down and then the Durolast membrane layed over that.
Everything looked good until the first rain when I saw new giant ponds all over. The averaged about inch and one half to 2 inches deep and were like 8 ft by 30 feet in size. Turns out the removal of the lightcrete plus the saggy joists created a sort of bathtub effect over every room. The joists are 2x8, 18 inch on center, 12 ft span.
The contractors solution to the ponding was to cut out a “trough” by removing a piece of the ISO board out of the 2 layers so that the water had a path out. (this is a flat flat roof, no parapet walls)
I thought this was a real hack way fixing things.
I wanted a uniform 2 layers of ISO board throughout and not having “missing teeth” all over. I would have preffered that the contractor build up the dips with thin layers of styroboard but because he would have to lift off the durolast membrane to do that and so he didnt want to. Then we argued, work stopped and now I’m not sure what to do next. The durolast itself is not affected by ponding but I find it hard to believe that ponding of this size is nothing to worry about. Drains are out too.