After a recent snow storm, we have accumulated almost 3 ft of :confused: snow on our house and garage. We are suppose to receive another foot before the week is over. Does anyone know how much a house roof can take? Is it time to start shoveling? Our home was built in 1982 and is a very sound structure with properly pitched roofs. There have been some roof collapes in the area, but just weaker carports, older sheds, and flat mall roofs.

Any opinions or advice? We really don't want to do it if it isn't necessary, but of course will do it immediately if there is risk of collape.

Thanks for all advice.

If the snow was "wet" snow versus the dry snow, then I'd look into getting it off the roof if you are expecting more on the way. It is the weight of the snow that is the question here. Snow is extremely heavy and definitely can do some damage.

If you feel okay with your roof's sound structure, then by all means don't remove it. But if will make you feel better removing it safely, then do so. In that scenerio it's better to be safe than sorry as you have no idea just how much snow will actually fall shortly and the weight of it added to the already 3' sounds like it could be a lot of extra stress on your roof.

The only person who can give you a truly accurate answer would be a structural engineer. We do not know the pitch of your roof or the size and types of decking or rafters. Even if you gave us this info I don't believe any of us are qualified to calculate the load bearing strength of a roof. Some hardware and home stores sell a snow shovel that has a 20' handle and can be dragged down the roof to pull off snow. I have one that just makes a thin cut under the snow and allows it to break free and slide down the roof.

Actually with that much snow in my opinion from experience with garage and home collapses remove it before it gets worse

Your house will also be designed for a certain snow load which will depend on the area you live in. i.e. houses in areas expecting more snow will have stronger roofs... so we can't give you an answer that 3' is OK... or too much.

If you are concerned, I like Ballengerb's idea of a long snow shovel. I know far too many people (2!) who have fallen off their roofs and seriously hurt themselves.

The local department of land use should have the design snow load information. If it's above that + expected accumulation, remove it quickly.

I cannot find the question that someone posed about snow on the roof. If I may, quickly... check in the attic and look see if the roof rafters are "trussed" some older homes are NOT! These are the types of roofs that are more likely to cave in under stress of heavy snow. Also if the rafters are only 2X6 without trusses. And,. even if the snow on the roof is "dry", it could well rain on it and multiply the weight factor! If one is really worried about it from his own observations, by all means, get the snow off!

Post moved. Black Bear, is this the right place?

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Originally Posted by RickJ

Post moved. Black Bear, is this the right place?

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Thanks for finding the right "question" site for me... I am getting used to this site!

Bb:
I did the calcs about 15 years ago. My expensive textbook in inaccessible at the moment. I did well in the class. I never did like analyzing trusses.

Another answer about snow on the roof... if the roof is more than one story (ranch style) by all means, get a pro to do it that is "insured" it will be well worth the price! As for me.. I have a small ranch... and when my cleaning off the roof is done... I like to freak out the neighbors by jumping off the roof into the snowbanks... it isn't that high really... ;o))

Contact the building department. They should have a copy of the plans from when the house was built. The plans should contain the answers your looking for.

I was asking a structural engineer about snow weight on a roof and he says that the building code in B.C. is rated for 3,500 lbs per square feet of roof. He says that it has to be over 3 feet in height before you should be concerned to lighten the load from the snow.
Hope this eases your concern.

It does depend on where you live. Each town/city/state has a snow load requirement. It can range from 30-10-20-10 to 70-30-20-20. The later loading being up in Maine, upstate NY etc. The wet vs dry snow aspect is incorrect. Snow is calculated as it's worst case scenerio. That would be wet. Your pitch, width, loading, type of wood used etc. determine the strength of the truss. If you do not have the original truss designs (with the specs)in your hands with the arch or structs, I wouldn't trust what you were told for a 'properly pitched' roof. Any pitch from .25" to 12" is a properly pitched roof. Whether it's up to proper building code is the correct question. Since 9/11 and a few other events, IBC/IRC has been taking it's place as the determining building code. If you worried about it, shovel off the snow at 2 feet. I've seen too many collapsed roofs from snow drifting and people not realizing their house or building was in danger. Minnesota Vikings Dome is a great example.
Anyone at the WTCA or http://www.sbcindustry.com/index.php should be able to point in a better direction. Asking a structural engineering is like asking the blind to lead the blind. Struct.Eng. Know nothing about truss design and don't trust one to be correct. I've corrected many engineers and architects about wrong loading on a project, which is frightening. Find the local truss manufacturer in your state or region and speak with the design manager. They have more training and knowledge then an engineer. Good luck and keep your shovel ready.