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Small Cabin Forum / Cabin Construction / Who's got 2x8's for their floor joist?
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WILL1E
Moderator
# Posted: 3 Mar 2021 13:11 - Edited by: WILL1E
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My original plan was for a 16' wide cabin this spring. Given the sky high lumber prices, i may need to dial things back a bit.

The cost savings is at least 27% if i go down from a 2x10 to a 2x8 joist system for my post/pier foundation system.

If i would go down to a 14' wide building using SPF lumber and the 40/10 loads, 2x8's would be sufficient to span the 2 beams. The span calc says 12'3". My question is, how spongy would that be in the middle for a single level cabin? Trying to determine the neccesity of adding a 3rd beam.

Nate R
Member
# Posted: 3 Mar 2021 13:29
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My house is 2x8s, 16" OC, and span is about 11'6". I think it's reasonable.

AKfisher
Member
# Posted: 3 Mar 2021 14:05 - Edited by: AKfisher
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My cabin I used 2x8's, they span a little over 7'. No spring.
Joists and Foam.
Joists and Foam.


snobdds
Member
# Posted: 3 Mar 2021 14:08
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Why not use TGI's and go with the original design. Besides,they're better in every way.

You only build once, build what you like.

gcrank1
Member
# Posted: 3 Mar 2021 16:18
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You could go 12" OC, but still be limited by the span. A few more joists to have a solid floor would make you happy rather than regret.
But...our 1st was 12x24 and our current one is 16x24. We Sure Do Like the 16 wide now!
I do remember thinking after building the 1st one that I wish I had done it 16.

lburners
Member
# Posted: 3 Mar 2021 16:26
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I have 2x8s with blocking mid way on mine.I just have the platform done at this point and cant feel flex but don't have the weight of the building on it. The blocks did seem to make a big difference though.
Im thinking about going rough cut 2x for my rafters. As an example 2"x8"x16' at box store is 30+$ and measures 1.5"x7.25"x16'. Rough cut is 16$ and is actual 2"x8"x16'.

ICC
Member
# Posted: 3 Mar 2021 17:34
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I would give some long hard thought into the width before making it narrower than first planned. We used the barn floor to draw things out before we built our first serious cabin. We had been thinking of keeping it small, a 12 wide x something. After laying out counter space for the kitchen, the wood stove, sofa, bed, etc we ended up at 16 feet wide and have never been sorry.

I know the lumber $$ today makes one wonder, but I would think about maybe not finishing the floor inside, or the inside trim, or something before downsizing unless I was very sure the smaller size was what I really wanted.

Just my 2 cents.

2x10, #2 SPF @16"OC can span 15'5" on the AWC calc. If you set those 2x10 joists on two beams inset just a half foot from the long side walls or so the floor would be very solid. That is what we ended up with 20 years ago, except our beams are a concrete block wall, but the dimensions and loads will be similar. That cabin has ceramic tile flooring on hardibacker on top of 3/4 Advantec. No cracks anywhere and that is a cabin that goes through several heat it up and cool it down cycles every winter.

gcrank1
Member
# Posted: 3 Mar 2021 19:33
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Boy, that barn floor layout idea is great; if only I could find my barn floor
The room(s) sure do tighten up once you put stuff inside!
Just for a sense of it, our 16 wide sure seems more than 4' bigger than the 12 was.

Brettny
Member
# Posted: 3 Mar 2021 19:41
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Spring in a floor is one thing. Sag over time is another. If prices are to high to build now dont. Wait it out. At $36 a sheet of 7/16 OSB idk how anyone can build anything thinking there going to get 3X what prices where about a year ago.

I say wait and save more money. If you cant maybe a camper would be better suited.

gcrank1
Member
# Posted: 3 Mar 2021 20:23
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Hear ya there!
We have a bunch of things we 'want to do' and were planning on for this year, but Not Now. If we didnt have the shack already there we wouldnt be building other than maybe a 'storage building' because after using it as the micro/mini cabin it would always be, well, our storage building on site.
That and a 10x10ish moveable deck and we'd be good to ride this thing out.
Sad thing is that as long as people are willing to choke and pay the price Im afraid the price is going to stay high; ie, what ever the market will bear is the limit.

toyota_mdt_tech
Member
# Posted: 3 Mar 2021 23:22 - Edited by: toyota_mdt_tech
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I have 2X8 floor joist, no span is over 12 feet, this is about max at 16" OC for 2X8. Zero spring, sheeted with 3/4" T&G PLYWOOD, glued and screwed.

rpe
Member
# Posted: 4 Mar 2021 07:27
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I used 2x8's on my 14x24 build. Beams are centered about 6" in from each side, so 13' span. This is rough-cut lumber, so actual 2"x8". Two rows of blocking, and some strategic twinning of joists in a couple spots where higher loads expected. No significant bounce. I went with 14' width, to allow for 16' rafters on the shed roof.

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