I just recently got a warm flat roof installed by roofers. They have used desmapol roofing. I see that once they have finished the roof, pretty much all board joints are kind of showing a small peak which may end up with water pooling. I took my friend who said it could be because the boards are not nailed to the joists. When the builders constructed the roof I specifically asked them if the obs (the board that goes on top of insulation) needs to be nailed to the joists but all they did was tape the joints between boards. The roofer says the desmapol product would allow for greater movement, but what I would like to know is if it is mandatory to nail the boards and insulation to the joists before laying desmapol. Please don’t confuse with the board that sits below the insulation,that has been nailed. My question is more on the top layer OBS. Please help.
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