How soon can built-up roofing be put over decking made of vermiculite concrete?
The concrete should be cured for at least three days or until it reaches the specified strength. Then it should be allowed to become substantially dry. It will be ready for application of built-up roofing when the surface is firmly bound and free of loose material and when it is hard enough to withstand the foot traffic of the roofing operation. It should also have a gray, cement-colored surface and look and feel dry. The hot-mopped bond coat can be applied smoothly to such a surface and will normally adhere well.