Weighing in on the weight of the snow

Posted at: 02/21/2014 5:16 PM
Updated at: 02/21/2014 5:44 PM
By: WNYT Staff

There has been a lot of concern over roof collapses lately.

The Capital Region has seen two so far because of snow.

One of them happened Thursday night in Troy, and rain is only making the snow heavier.    

If you do have a ton of snow on your roof it's never a bad idea to rake it.

Go out and grab one like this at your hardware store.

It'll do the job, but structural engineer’s say there's no need to hit the panic button.

When the roof gave way at this century-old building in Troy on Thursday night, no one was surprised.

Many say it's one of the worst winters we've had with snow and ice.

Over in Coeymans, snow fell from the roof of the post office onto an awning, causing it to come down.

With rain mixing with snow on top of roofs, some people feel it's a only matter of time before more roofs come crashing down.

Chad Ahr is not one of those people.

“I ride around and look all the time. There's a lot of snow out there. Everything looks pretty good right now,” he says.

Ahr is a structural engineer with Bellevue Builders Supplies in Schenectady.

He builds trusses; the skeleton looking structures that keep your roof up.

He says most modern homes built in the last 30 years, have them.

‘Your house will be fine, unless you have three feet or more of snow on the roof,” says Ahr.

Three feet on average, you'd be waist deep in snow.

Ahr's explaination is that trusses are built using this snow load map that takes a 100 year snow average.

It's different for every area.

For New York State, it starts out on Long Island where roofs are designed to sustain 20 pounds per square foot of snow.

“Just above the city, 30. As you get up to the Hudson Valley, 40. Our immediate area is 50.”

Fifty pounds per square foot translates to about three feet of snow.

Ahr says these trusses also have a safety factor.

He showed us computer models where they could sustain more than double the rating weight without failing.

Again, if you do have a ton of snow on your roof, you might consider raking it.

Ahr says all those calculations are for pitched roofs.

He says everything changes when you add the rain and a flat roof.