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carlveil
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# Posted: 24 Sep 2021 05:45pm
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Hi, Everyone, i gave been reading you for a while now and i'm finally ready to build. I'm uploading a cross section or my plan and i would really like your opinion. Now before you ask why i am building 12' x 24' , it's because it is a rebuild and i can't change the dimensions except for the height but again i'm limitée to 1 1/2 story. On the plan, i believe the use of 2x10s for the rafters and Floor joists is a little overkill so i would use 2x8 16"oc. Thanks in advance.
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carlveil
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# Posted: 24 Sep 2021 05:51pm
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I know most of you are not big fans of kneewalls but it's either that or gambrel roof and my wife doesn't like the style.ðŸ˜
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toyota_mdt_tech
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# Posted: 24 Sep 2021 08:37pm
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The 2X8 should be fine for joist, as for rafter, at 16" OC, 2X6 is fine unless you want space for insulation and venting. I have an attic so no roof insulation and 2X16, with the ridge, load bearing ridge beam?
ICC can help spec that all out.
It looks overkill, 1/2" sheeting for walls works fine, 5/8 for roof, but 1/2 works too. Floor, 3/4" T&G, glued and screwed.
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gcrank1
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# Posted: 24 Sep 2021 08:40pm
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My Cabin I was a 12x24 with a 12x12 loft, Swiss chalet style. The two of us found that size to be quite nice, though over time and aging/infirmities the loft with ladder only access became more of a storage space.
But hey, ya gotta put the extra stuff a cabin inevitably accumulates somewhere so you have room to live.
Kneewalls? Objection? Not from me. Its a cabin, not a house and the roof loads will be split on the 12' wide. Tie it up well at the loft joists and I dont think it will want to come down in a hurry.
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carlveil
Member
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# Posted: 24 Sep 2021 09:11pm
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Thanks toyota_mdt_tech , it is not a load bearing ridge and i plan to insulate from the exterior with foam boards.
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carlveil
Member
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# Posted: 24 Sep 2021 09:20pm
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Quoting: gcrank1 Kneewalls? Objection? Not from me. Its a cabin, not a house and the roof loads will be split on the 12' wide. Tie it up well at the loft joists and I dont think it will want to come down in a hurry.
Well the joists would sit on a 2x4 on a notch in the 2x6 studs and will be nailed with those studs.
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carlveil
Member
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# Posted: 24 Sep 2021 09:26pm
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I suppose it is better having full height walls like on the plan than having a separate wall on top of the full loft floor.
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carlveil
Member
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# Posted: 24 Sep 2021 09:34pm
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I did not mention it but i am from Québec so we get a lot of snow, (and wet snow in the last couple of years). That's why i needed to be sure it's strong enough whitout a ridge beam. And there would be a window at each end in the loft.
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ICC
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# Posted: 25 Sep 2021 09:24am
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You do not mention the spacing of the rafters. That influences the selection of roof sheathing thickness. Also to be accurate one needs to know the snow load in lbs/sq ft. That info should be available from local building authorities or maybe the province.
I use the AWC calculator to check the sizing. (that page takes a while to load) The species of the lumber is also needed as is the lumber grade.
The higher the snow loads the greater to outward horizontal forces at the rafter tails. Those push the wall tops out which is why rafter ties should be at wall tops and why kneewalls are not good design from a structural viewpoint.
The floor joist and ceiling joist/loft floor sizes are also dependent on species and grade of lumber and the joist spacing. Without that data we are guessing if a 2x10 is proper. Probably is okay but if you want to know for certain enter all that data into the AWC calculator.
The AWC is a US tool but the results should be valid in Canada too. Physics does not change at the border, even though the actual governing regulations might differ somewhat.
3/4" roof sheathing seems un-necessary. Even in 125 lb/sq ft snow areas here we use 5/5", usually on 16" centers. Walls don't need to be more than 1/2" as a rule.
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carlveil
Member
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# Posted: 25 Sep 2021 09:57am
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Thanks ICC, i Will check that calculator, am i wrong to think that the roof being steep 12/12 helps with the outward forces on the wall? From wath i have found, snowload would be 50 psf.
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ICC
Member
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# Posted: 25 Sep 2021 02:24pm
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Quoting: carlveil am i wrong to think that the roof being steep 12/12 helps with the outward forces on the wall?
The steeper the pitch the less the outward forces, so you are thinking correctly
A 2x6 of the usual species/grade available at the lumber stores should have no structural issues if used for rafters on a 12 ft wide bldg with even a 60 PSF snow load. Check but I think that would be about right. L/240 deflection
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carlveil
Member
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# Posted: 25 Sep 2021 02:41pm
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Thanks again, i:m more confident now. I'm gonna post pictures of the project and surely i Will have other questions.
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