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TNwoodsman
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# Posted: 23 Dec 2025 02:27pm - Edited by: TNwoodsman
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Hey guys I am soon to start the foundation of my 18x24-ft cabin. Some of the background info is 10 ft side walls. 12 by 12 pitch. Foundation will be 3 rows of 4 posts that are PT 6x6.
It will be fully sheathed. Floor joists are 2x10 with 2 x 2x10 rim boards on the exterior and 2x10 floor joists.
Originally, I was going to place a 24 foot 6x6 on the exterior posts and then place the 2x10 joists on top of the 6x6 beam that spans the 24 feet side. To me this seemed super strong. Is this way overkill? Should I just place the 2x10s on my 6x6 posts? The posts are one on each end and two in the middle every 8 feet to total 4 6x6 posts along the 24 foot side.
I love the sound of the 24 foot 6x6 beam but that won't be cheap and super heavy and harder to load/haul. If I went this route, I would anchor the 6x6 beam to the 6x6 posts and then anchor the 2x10 rim boards to the 6x6 beam.
If I may ask one more question....ridge board will be 2 2x10 with 2x8 rafters. Does this sound sufficient? Roof will be sheathed with osb or plywood and then metal roof.
Thanks for any and all input!
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DRP
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# Posted: 23 Dec 2025 04:47pm
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We've had several threads recently with wobbly piers, misplaced piers, piers without footings. Pier foundations are non code for good reason. The pic below is the code alternative, a "permanent wood foundation".
Do you know the local frost depth?
How much slope is there across the footprint?
6x6's are graded as posts not beams. I can do the math but at that span and load they will not be strong enough. Going back to the foundation I mention above, it supports the floor(s) uniformly along its length... before we go sizing members let's find out what the design and loads are.
10' sidewalls sounds like you plan on a loft above?
Are there porches or decks attached to the building?
What is the design snow load? If you don't know you can get it here;
https://ascehazardtool.org/
Use risk category I.
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TNwoodsman
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# Posted: 23 Dec 2025 05:03pm - Edited by: TNwoodsman
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Thank you for the reply.
The frost line is 10 to 12 inches in that part of southern TN/bordering Alabama.
We get about 2 or 3 snow falls a year at best here in southern TN. Usually a couple of inches.
According to that link, 18 lb/ft2 was the snow load value.
I was going to do a loft with 2x12 southern pine using jack studs and supported underneath by framing from kitchen, bathroom, and bedroom walls.
I was going to have a 4 foot porch.
I should mention that I am framing with 2x6s, 16" OC.
Happy to answer other questions.
Thank you!
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