12x12 Tiny Cabin Build - 2023

Adam Roby · March 15, 2023, 08:34:18 AM

I've decided to build a small cabin this summer, with the eventual plan to dismantle the old cabin and possibly replace it with a 3-walled lean-to tractor port of sorts. The old cabin fell into some rough times during COVID. Because of the border closure, I was not able to tend to it for close to 3 years, and racoons managed to get in and destroyed the place.

The new build is small, some may consider it just a shed, but I want it to be my tiny home away from home.
I plan on wrapping it with chicken wire before the siding and roofing, as well as the perimeter of the floor and under the floor. I will also be adding 1/4" mesh steel around all soffits and vents, to hopefully deter the mice as much as possible, and keep the racoons from destroying this building as well. I am building this alone with no access to water or electricity, and it will be completely off grid. As such, I will be building it a bit non-standard in that I will make 4' wide wall sections at home in my garage, which will fit in my 4x8 trailer, and assemble them like Lego at the build site. I am hoping I can get it dried in before the end of summer, considering I have other commitments which can take up some weekends (family, cottage we rent out, hunting season, etc.).

I will be using 9 foundation screws, and step one is just making sure I can screw them into the land. That process should start as soon as the ground is defrosted enough to get started. I've already purchased them, so I am committed now. I have to say, SketchUp is a fantastic tool to plan these kinds of builds. You run into so many virtual issues that you can address and modify now before the build even starts. I think my plan makes sense now, and I have almost everything detailed and measured out, as well as the materials and costs calculated.

I was originally going to have the main beams lie directly on the foundation screws to avoid any kind of pivot points, but I need to keep access under the building to insulate in the future, and I believe it will help keep the critters out. All supports will include 3/4" plywood gussets over the supports in all angles, which should help mitigate any lateral movement. Being a small building, it should be easy enough to keep level. I will post more images as the build starts.

Not sure on colors yet, but I did this as a test to see how it might look (vinyl siding with metal roof).

MountainDon · March 15, 2023, 07:53:40 PM

Is it possible to change the design to use foundation screws along the two eve sides with no central ones? That's just my preference for minimizing how much crawling under the building I might need to do in future years.

March 15, 2023, 10:07:30 PM

Do you mean if ever I need to level the building?
6 screws would probably be sufficient, but I am a bit skeptical of the 5000 lb claim of the foundation screws.
My thinking was that the center one would be the fixed one that is never adjusted, and I would use all the surrounding screws for the adjustment, thereby removing the need to crawl under (it is a grid of 3x3, 8 are on the perimeter with only one in the center. I would also have to beef up the main beams to support a 12' span instead of only 6. Do you think my logic is flawed there? It is definitely not too late to change the plans.

Adam Roby · March 16, 2023, 05:52:30 AM

I slept on it, and realized you probably mean just the center beam can changed, keeping all outer beams the same. That would mean 8 foundation screws instead of 9, and only the center beam can have a larger size. In reality, the perimeter is where all the weight should be, and the center screw will only really deal with floor bounciness... I will do some more drawings today, thanks for the suggestion,

NathanS · March 16, 2023, 07:40:17 AM

All the weight (not a whole lot of it) goes to the to eave walls. At 12' your floor doesn't need a center support just some 2x10s or 2x12s, all 3 of the center screws aren't necessary - as long as you're doing joists and rafters.

They make marine boat woodstoves that would be perfect for a little space like that.

Just my opinion, you could lay down some solid CMU blocks and frame right on those. If the building moves its light enough to jack up with a car jack and shim.

I would consider framing the entire floor and subfloor with pressure treated. Insulate on top of the subfloor with 2"XPS. Anything underneath will turn into nest material for animals, I think.

March 16, 2023, 09:58:28 AM

Quote from: NathanS on March 16, 2023, 07:40:17 AMI would consider framing the entire floor and subfloor with pressure treated. Insulate on top of the subfloor with 2"XPS. Anything underneath will turn into nest material for animals, I think.

I was contemplating that when the floor would have been much closer to the ground (had I left the beams lay directly on the foundation screws). Since moving it up, I should have 18-20 inches above ground, and I seem to remember one of the Don's mentioning that was a safe zone for non-treated. The only insulation I plan on adding is spray foam, I wonder, could that be used as nest material? I was also concerned having pressure treated on the floor (off-gassing), since insulation will only happen in 1-2 years, and I will be using it in the meantime.

Blocks are also difficult for me as I have a bad back, after my last surgery my doctor advised against any heavy lifting. I tend to work like a madman for 16 hours straight, then have to lie on a sofa for 2 weeks to recover. That was also driving the foundation screw idea.

jsahara24 · March 16, 2023, 11:49:21 AM

I believe 18" is the separation needed to use non PT lumber.

I just had the floor of my cabin spray foamed, we did 2". Amazing the difference it made, highly recommend. For a small occasionally used cabin I don't think you need any more than 2". And I don't see how animals could get into it, but I guess I'll have to report back on that.

NathanS · March 17, 2023, 07:30:29 AM

I'm not sure about the spray foam. Before I enclosed the eaves on my house, starlings would dig into and nest in the polyiso insulation. It's incredible the damage animals can do. Chipmunks actually chewed through the wood after it was enclosed and I believe they nested in it too.

Adam Roby · March 17, 2023, 06:35:36 PM

Quote from: NathanS on 3/16/2023, 8:40:17 AMThey make marine boat woodstoves that would be perfect for a little space like that.

I remember seeing someone with one of those on here a couple years ago. It was a very attractive unit.
I was leaning more towards a small direct-vent propane heater. They sell the 11,000 BTU units at a decent price. They also take very little room, which helps in such a small structure. Still haven't decided though.

Something like this:

Adam Roby · March 18, 2023, 01:10:08 PM

If I went with the recommended 2"x10" without center beam, would the supported ends need to be double up, or could they be like this?

NathanS · March 20, 2023, 06:43:25 AM

https://up.codes/viewer/new_york/irc-2018/chapter/6/wall-construction#R602.7

By the book, I believe you would want to use the spans for table 602.7 "Roof, ceiling and one clear-span floor"

A doubled 2x10 can span 6' 1" in 50psf snowload.

Alternative would be to add another screw to shorten the load bearing wall span.