We have about 3'-4' of snow on the ground and I'm seeing a lot of people hiring roofers to clear the snow off their roofs. Is this necessary to prevent collapse? I'm in New England and it's a fairly new house (1980's). The trusses are 2x8 and 16" to center.
Right now there's about 1.5' of snow on the roof as best I can tell. We have another 1-2' coming tonight and tomorrow.
Thanks.
2015-02-08T15:03:37Z
Also, it's a 2-story house and there's really no way to use a roof rake. I don't particularly want to get up there, either.
redstapler522015-02-08T15:14:12Z
You should be ok with that much snow. A roof can hold a lot of weight. A quick check on whether you may be in danger would be to go up to the second story and open and close the interior doors. If any of them rub the door frame and didn't before you got all the snow, you need to clean your roof off ASAP. Snow can weigh up to 20lbs per cubic foot.
The building codes calls for a roof design between 25 and 50 pounds per square foot. Fresh snow can weight about 6 to 12 pounds per cubic foot. So 1.5 feet of snow would put a load on your roof of between 9 and 18 pounds per square foot. At 2 foot of snow the load will be between 12 and 24 pounds per square foot. If it gets to 2.5 feet then the weight will be approximately 15 to 30 pounds per square foot. That is the time when I would start to think about getting someone to get some of the snow off.
The problem will develop when the first warm storm comes in and you get rain on the snow. The snow will hold a great amount of water before it melts. This may make a 10 pound load of snow per square foot suddenly be 200 pounds and then is when the roof will collapse. Either remove the snow your self or hire it done before the storm comes in.
Just a shot in the dark, but won't sun exposure melt the snow before it has a chance to build? I'm unsure of the load a roof can withstand but I am very certain weight was taken into consideration when building your home.
Are you sure they're not having it remove for other reasons? Such as heat containment or drainage issues?
Part of the calculation is based upon the angle of the roof - the pitch. This is factored in for the 100-year snow design load when they build houses to building code. If you are concerned, you could hire a structural engineer to assess your building.