Real-Life Roofing Horror Stories

Building Operating Management, May 2004 by Warseck, Karen

The result of the gaps was that the membrane was no longer being supported by the boards. Because the rest of the membrane was firmly adhered to the insulation boards, the movement of the roof caused the membrane to stretch and relax at its weakest location - the insulation joints. It was the same effect as bending a piece of wire back and forth - eventually it snaps. Moisture was getting into the system at the broken membrane and running through the gaps in the insulation boards, causing the long thin blisters in areas that had not yet split.

The only way to fix this roof would have been to cut every joint, fill the gap with insulation and patch the membrane. It was readily apparent that it would be more cost effective to reroof. Because of code changes between the time the building was purchased and the time it was reroofed, the costs escalated - to the tune of $400,000.

Moral: What appears on the surface may not be what's going on underneath.

LITTLE ROOF, BIG PROBLEM

The biggest roof problems can appear on the smallest roofs. Consider a 40-by-20-foot building with a coal tar pitch roof. The roof was installed over a dead-level deck. Water ponded heavily. The roof had a leak that no one could find. Unfortunately, the roof was above equipment for the local electric company, and the water ended up in the electrical works.

The problem was that there wasn't any problem, at least none that was readily apparent to an observer on the roof.

An examination of the interior of the building around the location of the leak found nothing suspicious. Water staining, for example, would have indicated the source of the water entry. Since the water was puddling on the floor near a wall/floor intersection, the consultant initially thought the water might have been coming from below. The walls had been recently painted, obliterating any water staining that might have revealed where the leak occurred. Only a concrete patch that was lighter than the surrounding floor was out of the ordinary. Nearby was the outline of a wall that had been removed. Neither showed that there was a leak anywhere near.

Results of a roof survey were not conclusive. The membrane and flashings were in good condition and not an apparent source of leakage. A moisture survey found no areas of wet roofing. In addition to the roof, the walls and windows were checked, but even these steps didn't reveal anything that would explain how water was entering the building.

By pure accident, the roofing consultant involved tripped on a small loose spot on the roof. What appeared to be an unbroken patch turned out to be only a flap artfully hiding a hole through the deck. Everyone had been walking around this hole without noticing it was there. It turned out that at some point in the past, someone had removed a bathroom from the substation and installed equipment and a wall that hid the vent pipe hole from view. They removed the vent pipe but since the remaining interior pipe was cased in a wall, they never patched the roof. The coal tar pitch had cold flowed around the opening enough to stop water from spreading throughout the roof, but not enough to stop water from going down the hole in the ceiling, into the wall and out onto the floor.