I’ve been searching through my code book with no luck. What a read ! its like pulling teeth. What I want to know is what lumber to use for a shed roof (rafters) on a carport addition I want to build that is 30 ft square. It has a low slope roof (about 2/12) There is going to be a beam with a post in the center of three 16 foot 2×10 glued and nailed. (cut to 15 ft of course)
Do I need to use a 2×10 or 2×12 to span the 15 ft to the beam at 16 ” centers. I live in B.C Canada so snow load is a concern. Although not to much Where I live.
Thanks for your help
Replies
"not too much" is not too specific.
You need to have specific number for live load to get a specific answer
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For snow We get three or four feet at the extreme but the last few years 2ft and under is a safe bet.
that is not the specific I meant. Live loads are measured in pounds per square foot. Local building codes vary on this. In southern states ( where charlie must be from, given the lightweight design he suggests) you can get by with as little as a 15# live laod design. In some northern snow areas, design loads can be from 70 to 110#/ sf. You need to ask your local authorities what min. live load they require for a roof.
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In southern states ( where charlie must be from, given the lightweight design he suggests)
nope...I'm in the great state of Minnesota... where snow is a plenty. I was just having a go at the lad. I actually tore apart a carport that had that framing on it....2x4 24" oc with 3/8" osb with 30 yr fiberglass shingles, pitched just under 3/12... it was only 15 mos old (HO built it) and was leaking/saggin like crazy. HO couldn't understand why???"knowledge without experience is just information." Mark Twain
" it was only 15 mos old (HO built it) and was leaking/saggin like crazy."perfect example why she shouldn't build it that way but find out what her required snow loads are and design to that.
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I'd just use 2x4 24" oc with 3/8" osb...
I would consider engineer I joist if it is going to be enclosed.or if you like the look of them...
but as Master Piffin has stated, without load considerations it would be hard to dictate size and spacing.
There is going to be a beam with a post in the center of three 16 foot 2x10 glued and nailed. (cut to 15 ft of course)
this doesn't make sense to me...but it is late...are you saying that the carport is going to have a post from the footing up to the beam directly in the middle of it?
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your drawing is right the rafters will come down and sit on the beam with a two foot lap.
First, you need to know what the 'ground snow load ' is for your locality.
then the 'roof snow load can be found. (safety factored)
Your best bet is to contact a 'truss 'builder in your area and get a quote.
The trusses are built to withstand the loads. They are quite less costlier than you think.
And you will have 'peace of mind' when that big heavy snow storm dumps 3' of the stuff on your roof.