A high-tech monitoring system could offer advance warning of an impending roof collapse.

It's the day after Thanksgiving, the biggest shopping day of the year. Outside the weather has turned nasty, and snow and ice are piling up on your roof, causing structural stress. As the shoppers in your center merrily pick out their holiday gifts, the roof sags, bends ... and finally collapses, causing vast monetary damages, bad press, and even potential lawsuits from injured customers.

Unlikely? Yes, but not impossible. Roof collapses are rare, to be sure, but insurance companies and unlucky building owners could tell you many stories with similar unhappy endings. Most center owners are aware of this, but their prevention program usually consists of little more than periodic inspections and regularly scheduled roof replacement.

Regular maintenance is always a good idea, but one company has come up with an idea that provides an extra measure of safety.

Safe Roof Systems of Mattapoisett, Mass., has developed a device that can detect the slightest distortion in a roof's shape through the use of lasers. Jeff Canty, president and CEO of Safe Roof Systems, invented the DMD 1000 system in 1995 and received a patent for the device in 1996.

Realizing that lasers were already being used for fine measurements in other fields, it seemed logical that this technology could be used as a warning system for stressed roofs.

Even if this technology is space-age, the concept is fairly simple. A laser and receiver are mounted on the roof, with targets attached to the bar joists. If the roof sags, either due to structural failure or increased loading by ice and water, the targets interrupt the laser beam and trigger an alarm. The system is so sensitive that it can detect movements as small as 5/1000ths of an inch!

The DMD 1000 was first installed in buildings in 1998. The second building ever to use the system, Showcase Cinema in Manchester, Conn., saw fairly immediate results. On Jan. 14, 1999, mere months after the system had been installed, a nasty winter storm hit the Manchester area. Eliot Finn, senior project manager for Showcase Cinemas, wrote to Safe Roof Systems and described the situation.

"The downspouts froze, the building was full of ice, and then came the rain," says Finn. "The on-site manager was notified by your system and was able to take quick action in getting a roofer to site to pump the water off the roof...There is absolutely no question in my mind that the monitoring system provided the cinema manager with the needed information ... to rectify the problem before it became catastrophic."

Showcase Cinemas estimates that more than $1 million in damage was avoided thanks to the DMD 1000 system, not including the lost revenue that would have occurred from having the theater closed for eight to ten weeks. Patrick Watson-Hogan of Old Colony Construction Corp. also wrote to Canty, saying that from now on they "would highly recommend the system to any owner, just as added security and peace of mind." Two things that any building owner can appreciate. For more information, call Safe Roof Systems, (508) 748-1500.