What is the effect of ponding water on a built-up coal tar roof?

Answer 1

Talking to your local roofing supply can find you a pitching solution. This usually involves a creating , out of foam board , a dedicated pitch plan for your roof. the pieces will come numbered and re-establish a drainage plane, then resurfacing over the foam buildup.

Answer 2

Water left on the roof in a pond will eventually find its way into the surface of the tar paper, then it will deteroriate that tar paper causing the molecules in the tarpaper to expand apart. This process will be repeated many times and then eventually the layers of tarpaper will detoriate to the point at which they will fail.

I dont advise building up the high spot with felt or adding additional layers of tarpaper in that area. What will happen is that pond will find another spot to make its home so that is not advisable to do. And you will wind up with many end areas which are easily penetrated by water and will begin to curl upward.

What i do advise is to consider adding an a finely crused stone to ponded areas as they appear, filling those with stone. Thus it will not hold nearly the water after a rain and the little water left will evaporate very rapidly due to the huge surfaces of the crushed stone. For a residential house, you can buy a black crushed stone the consistency about 3/32 of an inch and its apperance will be entirely satisfactory.

Answer 3

Ponding is never good on a rooftop. Roofs are designed to drain water, you need to find out why yours isn't and fix the reason. May need to build up the area where the pond is (felt paper and more tar on top) to get the water to drain off... need to make a high spot instead of the lowspot it is...