Real-Life Roofing Horror Stories

Building Operating Management, May 2004 by Warseck, Karen

From UNDERSIZED DRAINS TO SUPER-SIZED BLISTERS, these frightening tales show dangers of projects gone awry

It's a familiar scene from late night television: An unwary peasant, out on a moonlit night, hears an ominous sound and turns. . . There stands a vampire or werewolf. But not all horror stories are safely confined to the television set or movie screen. When it comes to the roof, blisters and leaks can be almost as terrifying as the demons of the night - and far more real.

In many cases, these real-world roofing horror stories teach important lessons, partly because they are recurrent nightmares for facility executives.

Consider this example. A leaky structural standing seam metal roof was only f O years old - not old for a metal roof - but it had leaked on and off since it was installed. Because of the nature of the primary tenant, even a small amount of leakage was unacceptable.

The owner hired a roof consultant to provide plans and specifications for reroofing the building. Because it was not feasible to remove the structural standing seam metal roof, leaving the building wide open to the weather, three separate schemes were designed to get the best price for the new roof. all were lightweight to avoid overloading lhe pre-engineered structure.

Because the owner also wanted to eliminate the interior gutter system, a source of much of the leakage, the drainage was redesigned to take advantage of the existing overflows, making them the primary drainage. The construction documents detailed three new overflows at each drain to be added to the precast concrete parapets to assure that water on the roof would be quickly removed. The new deck was to be supported by steel angles attached to the concrete walls.

The roof was bid without the involvement of the consultant and installed. Fifteen months later, it collapsed following a night of heavy rain. The original consultant was called back to determine what had happened. One look at the building from the outside told the whole story. Both the overflows and the steel angles intended to support the new deck had been eliminated by value engineering between the owner and the roofing contractor, who was not familiar with the design and didn't understand why it was done the way it was.

Because the overflows were not installed, the estimated 9 inches of rain from the previous night could not exit through the main drainage fast enough. The weight of the water accumulated at the drain, where it overstressed the deck and the structure, and the building came down at a cost of about $2 million.

Moral 1: Keep the person who designed the roof involved until the roof is installed. Moral 2: Value engineering is just another name for "let the buyer beware."

ARSENIC AND AN OLD ROOF

Picture a hazardous waste containment facility with large tanks of arsenic being stored until it could be properly disposed. The vats were sitting on concrete secondary containment. The owner hired an unlicensed consultant to design a new roof for the building. The project was bid and awarded to a reliable contractor who followed the consultant's documents to re-cover a built-up roof and even added a little extra gravel to the roof to be sure it was well covered.

After the new roof was installed, there were approximately 10 pounds per square foot of built-up roofing and 17 pounds per square foot of recover roofing material on a structural steel deck designed for 20 pounds dead load per square foot and 20 pounds live load per square foot. In addition, re-cover drains were installed that reduced the size of the drainage pipes to about one-third of the required amount.

Because the size of the drain was reduced, the water built up on the roof to the overflows during the next heavy rain - four inches of water at approximately 5.2 pounds per square foot. Guess what ended up with the arsenic in the secondary containment? You do the math.

Moral: Hire a competent consultant who makes sure the structure can withstand the weight of the designed roof.

A 30-FOOT BLISTER WAS ONLY THE START

A property manager was frantic. Her predecessor had installed a new roof on the building six months earlier. Now this brand new roof was already leaking badly, and the manager was beside herself about what to do. An inspection of the roof revealed very large blisters - one extended more than 30 feet. Further investigation revealed that the new roof had been installed over an existing membrane, but the existing, poorly installed pitch pans had been left in place. Water had gotten into the old pitch pans and spread out from there. Wrinkles in the membrane left long thin tubes between the plies to funnel water into the roofing. After only six months in use, a moisture survey discovered that nearly 80 percent of the roof was completely saturated.

The property manager then looked at the contract to try to resolve the problem with the contractor who had installed the roof. To her horror, she found that the previous property manager had failed to get a signed contract from the roofing contractor. That property manager had spent $57,000 to replace a roof without a signed contract.