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Liamey
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# Posted: 12 May 2013 03:30pm
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Hi,
It's been a while since I was last on, but i am pleased to say that I now have my Crown Land permit.
I hope to build a 16x24 cabin storey and a half. I do have one question though.
I had planned on 6x6 PT posts with triple 2x10 piers (3 piers with 4 posts 12" offset). 12 posts in total.
Now I have read that if i use the right sized floor joists cantilevered on top of the beams I might not need a central pier - is this right? Would 2x8 floor joists be able to span 14 odd feet?
Any input you have would be greatly appreciated 
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soundandfurycabin
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# Posted: 12 May 2013 04:22pm
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What you are calling piers are actually the beams. 14' is a bit too far for 2x8's. You might get that distance with select structural grade lumber and a 12" joist spacing, but the floor would probably still be a bit bouncy. Better to go with 2x10's at 12" spacing or 2x12's at 16" spacing.
A second reason for not using 2x8's is that with 2x8's the cantilever would be limited to 16", but with 2x10's or 2x12's you can go up to 24". Either way though, the cantilevered joists are not supposed to support a second storey. The building inspector might allow the loft if you marked it on the plan as "storage space" rather than living space. This is from the B.C. Building Code, but Ontario's will be nearly identical:
9.23.9.9. Cantilevered Floor Joists
1) Floor joists supporting roof loads shall not be cantilevered more than 400 mm beyond their supports where 38 mm by 184 mm joists are used and not more than 600 mm beyond their supports where 38 mm by 235 mm or larger joists are used.
2) The cantilevered portions referred to in Sentence (1) shall not support floor loads from other storeys unless calculations are provided to show that the design resistances of the cantilevered joists are not exceeded.
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Liamey
Member
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# Posted: 12 May 2013 04:54pm
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Thank you for the quick reply - much appreciated. I almost have the land cleared so still a little time to get this right. I'm in Newfoundland and there is no building code for a remote cabin. However I would like to make it safe.
The extra storey would be a half storey and even that would be partial (enough for a bed - everything else would be open). Envision that small cabin plan (something like build this cabin for under $1000) on the net where there is a small deck with bedroom loft over it (everything else open so not an entire floor on top.
Would I be better not canterlevering? My though for doing this was to have the posts somewhat under the cabin away from the elements (snoe etc)
I really would like the strongest foundation structure using the post and beam method bearing in mind we receive a fair amount of snow in the winter. Might i be better having 3 beams with 4 posts on each not cantilevered but rather flush between the beams?
Any thought son this would be greatly appreciated before i start to dig holes.
Thank you
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soundandfurycabin
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# Posted: 12 May 2013 05:24pm
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If there's no inspection then I'd sure go with the cantilevered joists and have no concerns about a lightly loaded sleeping loft. Keep in mind that you still need the same footing area, so with 8 posts instead of 12, each footing should be about one and a half times bigger. The two beams also will carry more weight so they also need to be larger. The other option is to increase the number of posts from 4 to 5 per side.
Good luck!
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ICC
Member
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# Posted: 12 May 2013 05:54pm - Edited by: ICC
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Quoting: soundandfurycabin 1) Floor joists supporting roof loads shall not be cantilevered more than 400 mm beyond their supports where 38 mm by 184 mm joists are used and not more than 600 mm beyond their supports where 38 mm by 235 mm or larger joists are used.
Wow! That is a whole lot more generous cantilever allowance than what the USA codes permit!! Without having an engineer look at and approve we are limited to a cantilever being no greater than the depth of the floor joist for something like the entire sidewall as you describe.. Our wood is the same. In fact it is often a CanFor product. Just a different way of appraising the strengths or design I guess. Or perhaps a special rule for utility buildings? ???
What's the snow load possibility? That can be greater than a second floor. I'd be careful and use small cantilevers, if any, if the snow load gets over 30 psf.
How's the wind? High winds getting under a building can also be a problem. Skirting the bottom around the posts can protect them and keep the wind out. Metal roofing work good for skirting.
Use this to help size the floor and ceiling joists and rafters
G/L
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gunslinger22
Member
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# Posted: 26 Jun 2013 02:13pm - Edited by: gunslinger22
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Any idea what constitutes a temporary foundation in BC?
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