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optimistic
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# Posted: 25 Jan 2023 02:15pm
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Hey all! long time. Quick question..
I am planning on extending my 12x12. I hope to add another 12x20. It will just be a big living room essentially (with fold out sofa). Ceiling height will be about 10ft. I am thinking to make two 20ft double 2x10 (glue and bolted) from 2x 2x10 with 12ft 2x10 joists between to span the 12ft. Each of the beams will be carried by 5x 4x4 sitting in those cement bases (so I will have 10 all together)
https://www.homedepot.com/p/11-5-in-x-8-in-x-11-1-2-in-Concrete-Deck-Block-10550005/1 00350712
Should be fine right?
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Brettny
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# Posted: 26 Jan 2023 10:24am
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What's the foundation like of the current building? 2x10 will be fine for floor joits, just bring in the beam/girder a bit on each side.
As for how you make the beams/girders.. you really want support under each break in the lumber. They do sell 20' lumber so i would use that. I would also use doubled up 2x12x20' for the beam so you can use less blocks/posts.
Also 4x4 posts really have no business being in a foundation. Use 6x6 and notch them to accept your beam/girder.
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NorthRick
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# Posted: 30 Jan 2023 02:33pm
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Quoting: Brettny Also 4x4 posts really have no business being in a foundation. Use 6x6 and notch them to accept your beam/girder.
I have 4x4 posts holding up my 12x16 cabin. Longest ones are about 3', shortest about 1'. We get some significant snow loads - over 80 psf some years.
That said, a 6x6 notched for the beam to sit in and get bolted to the 6x6 is a great way to go.
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gcrank1
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# Posted: 30 Jan 2023 08:04pm - Edited by: gcrank1
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Ime, buildings are heavier than we expect a box full of air to be.
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Brettny
Member
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# Posted: 31 Jan 2023 06:01am
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Quoting: NorthRick have 4x4 posts holding up my 12x16 cabin. Longest ones are about 3', shortest about 1'. We get some significant snow loads - over 80 psf some
How are you securing the top and bottom of the 4x4 post.
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NorthRick
Member
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# Posted: 1 Feb 2023 07:44pm
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Quoting: Brettny How are you securing the top and bottom of the 4x4 post.
One of those pyramid shaped deck blocks with one of those adjustable brackets that fits into the hole in the deck block.
On the top they are through bolted to the longitudinal beams with 45* 2x4 braces on the longer posts.
I keep meaning to take a few photos of the foundation since the topic comes up so often but never seem to remember when out there. I do have a photo of the snow load though.
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Brettny
Member
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# Posted: 1 Feb 2023 08:22pm
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What your describing wouldnt be my first choice for a foundation with the snow load I see in the pic.
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NorthRick
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# Posted: 2 Feb 2023 04:34pm
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Quoting: Brettny What your describing wouldnt be my first choice for a foundation with the snow load I see in the pic.
I understand why you would say that, but there were a number of factors at play at the time and, it seems to be working.
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