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View Full Version : Deck roof construction calculations


pwd77
Sep 7, 2009, 03:23 PM
I'd like to put a roof over my deck. Its easy to find tables to calculate timber for decks, but not for roofs.

Is the load calculation the same for a roof/deck cover as a deck (e.g. 10 lb/sf dead load, 40 lb/sf live load)? Does one treat the live load of a roof (snow) the same as live load for a deck?

24336
the deck is 12' deep, and there is a beam down the center that I can use to support the posts of the cover. I plan to cantilever out 2-3' (3' shown).

Why does it matter? I'd like to use light lumber (2x6) AND space the posts(~10') out so they don't get in the way too much.

thanks!

jon123
Sep 9, 2009, 06:03 AM
beam down center? Hmm.. you must make sure you are up to code in your area, consult with your towns building dept... it looks like you will need a bld. Permit for such a project even if it is just a replacement project.. the girder beam has to be up to spec. the roof cantilever should be within maxium load for 2x6 @16oc sheathing minimum thickness I think for low pitch is 3/4 plywood or compatible materials. Your footings will likely need inspection too.. in my opinion, you can take that sketch with you downtown and explain/ask a town inspector what is needed or required for such a project. I'm sure up in the air work like that is worth getting a permit

zippit
Sep 9, 2009, 06:11 AM
Can you shoot some pic's of your existing structure ?underneth as well

pwd77
Sep 9, 2009, 07:14 AM
Thanks, Jon, zippit
I live in the boonies, so there are no permits, but no one to ask questions either. Armed with information (from helpful replies like yours) I can call neighboring cities.

I'll put up a few pictures to better show the situation later today, zippit

jon123
Sep 9, 2009, 03:09 PM
You know pwd.. a closer look at your sketch shows that you intend to secure your roof rafters to the siding/sheathing?. you maybe better off cutting and laying you rafters along the original roof rafters.. cutting a small birdsmouth to rest on the top plate and secure your new rafters by nailing into the original roof rafters.. you will be better off with a roof that continues through without any breaks.. but whatever floats your boat.. I've seen small awning/shed rooms done that way too.

pwd77
Sep 9, 2009, 06:58 PM
you know pwd.. a closer look at your sketch shows that you intend to secure your roof rafters to the siding/sheathing?.. you maybe better off cutting and laying you rafters along the original roof rafters .. cutting a small birdsmouth to rest on the top plate and secure your new rafters by nailing into the original roof rafters..you will be better off with a roof that continues through without any breaks .. but whatever floats your boat..i've seen small awning/shed rooms done that way too.

Good point, I think I would have to have a pro do that, and it would look much cleaner and be taller (good). May I'll wait on this...