Green Roof Collapses in Illinois

[XemaSab]

Green roofs have become increasingly popular in the United States as a way to beautify and insulate buildings and reduce heat pollution in urban areas, but last week one drew attention for a far different reason: it collapsed.

A 700-by-50 foot section of a roof over a parking area buckled on Feb. 13 at a garden pond construction and supply company in St. Charles, Ill., west of Chicago. No one was injured in the collapse, which occurred on a Sunday afternoon when few people were working at the company, Aquascape Inc.

Nearly a week later, investigators were still waiting to try to determine why the roof collapsed, said Ed Beaulieu, a company vice president. “We have to shore it up to make sure it’s safe” before the investigators can examine the steel structure, he said.

Mr. Beaulieu said that the area had received a record snowfall and then, two weeks later, temperatures climbed above freezing. “The collapse happened right at the beginning of the thaw,” he said, leading to speculation that ice on the roof might have prevented meltwater from draining off. “But right now no one really knows.”

http://green.blogs.nytimes.com/2011/02/18/green-roof-collapses-in-illinois/?hp

[mopinko]

1. here's a clue about your theory-

water weighs the same whether it is ice, snow or liquid. so that melt water was not any heavier than it was when it was snow.
keep thinking there, folks.

[OnlinePoker]

2. It depends on where the drains are.

If the roof was sloped and all the melt water pooled into one area to drain (which were blocked by ice), that space would, indeed, have a lot more weight on it than was spread across the whole surface as snow. Looking at the supports under the roof, it didn't look too stable, but that's just an opinion from this non-engineer.

[mopinko]

3. people don't always appreciate the weight of these green

roofs. we were planning an addition to our house, and we asked for a green roof and the stupid architect never bothered to calculate the load. fortunately someone else told up the place wouldn't hold it.

and you are correct, i did not think about the movement of the water.