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Small Cabin Forum / Cabin Construction / Square Footage
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paulz
Member
# Posted: 9 Dec 2011 21:50
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Greetings and thanks for all the great information on small-cabin.com!

I have my land, milling my own wood for my cabin. I have settled on 300 sq. ft. mostly because my local building codes allow that size of a building without a permit. I see many go with 14x20 but I've been thinking 15x20 to get the full 300 sq. ft. What is the reason for the all the 14x20s, just the even numbers?

Thanks!

Just
Member
# Posted: 9 Dec 2011 22:26
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store bought lumber dosen't come in 15 ft. lengths .you would have to by enough lumber to build a 16 x 20 cabin and through away the excess. plus a 2 x10 floor joist can only span 14 feet by code, but you will not have these problems as you will have no inspection and you are using your own lumber !! good luck !!

Nirky
Member
# Posted: 9 Dec 2011 23:54
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In my jurisdiction the square footage is not determined by exterior dimension, but rather by interior floor space.

soundandfurycabin
Member
# Posted: 10 Dec 2011 04:49
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There can be advantages to sticking to certain spans and widths just because they define cut-off points in the building code. For example, in the building code for my area, the ridge beam spans are based on building widths of 32', 28', 24' and 16'; and, footing requirements are based on a max joist span of 16'.

Lumber is sold is 2-foot increments and plywood comes in 4-foot wide sheets, so staying with even dimensions might save a bit of cutting. But floor joists have to be trimmed to length anyway, and the joist and floor sheathing cutoffs can be used elsewhere. ex. If you cut your joists from 16-foot lumber, the cutoffs could be used for mid-span blocking.

A lot of siding materials are also sold in 2-foot increments but that's not going to be much of a factor when you have windows and doors breaking things up anyway.

Foundation forms are designed for 2-foot increments. If you are hiring a foundation contractor to pour a basement, you might save a bit of cash by sticking to a 2-foot grid.

The upshot is that there are some reasons for people to stick to even widths, but those reasons really aren't all that compelling. If an odd width works better for your plan, go for it.

paulz
Member
# Posted: 10 Dec 2011 09:22
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Thanks for the replies guys. I did call my building dept. and asked how they determine the square footage, they said outside dimensions, I guess that's the norm rather than exception. I really would like to get the full 300 I'm allowed. 14x22 gets you 308, and knowing me I'd probably get called on it.

MtnDon
Member
# Posted: 10 Dec 2011 11:22
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Yes, for determining permits and costs, outside measurements are used more often than interior. It's easier to measure the exterior than a bunch of interior spaces.

So make it a tad narrower or shorter. Our cabin is 15' 9 1/2" wide as measured before the siding was applied to the sheathing.

Rob_O
# Posted: 10 Dec 2011 13:49
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Quoting: soundandfurycabin
plywood comes in 4-foot wide sheets


But to make things more confusing a 4' sheet of tongue&groove subfloor only covers 47.5" so your 16' wide cabin becomes 15' 9.5" if you 're buying off the shelf (that number look familiar?)

MtnDon
Member
# Posted: 10 Dec 2011 14:08
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Someone has been paying attention.

Actually I still had to trim a little off the final sheets but that was easy by snapping a chalk line then cutting it all ain one pass. Better than trying to pice in an inch or so too.

Personally I don't mind a little material waste if it allows me to achieve exactly what I want or makes something else easier to put together.


If I was aiming for 300 sq ft I'd first ask if the measurement is taken off the final siding materials dimension or the rough sheathed wall. Then size it something like 13.75 x 21.75 = 299.06

soundandfurycabin
Member
# Posted: 10 Dec 2011 16:23
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Quoting: Rob_O
a 4' sheet of tongue&groove subfloor only covers 47.5"

That depends on how it's manufactured. If they just offset the center plys, then it will remain a full 4x8 on the face. But it's a good idea to confirm ahead of time if you are counting on full-size sheets.

MtnDon
Member
# Posted: 10 Dec 2011 17:33
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This has been mentioned before. Every manufacturer's T&G product I've ever seen has been 47.5, more or less. But no doubt I've not seen them all. Different manufacturers also mill different pattern T&G's. Also might be worth mentioning again that the T7G will not fit together to provide a joint that appears butt tight. That's done on purpose to provide the required expansion clearances.

tusk
Member
# Posted: 13 Dec 2011 18:58
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consider 12 x 25... depending on what rooms you need, you may find this the most efficient dimensions.

if you'd like a crude floor plan, I have several with 12' widths.

tusk

tex
# Posted: 22 Jan 2012 17:38
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Could you send me the floorplans for 12' x 25'?

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