Small Cabin/Shed construction
Rodetyl
| Posted in General Questions on
Hello, I’m looking to build a semi remote small cabin in Alaska (Zone 8). It’s going to be 12×24 dry cabin on a skid foundation with a lean-to roof and heated with a wood stove. Ideally this is a temporary cabin for us, just a place to put up quick and live in while we build something bigger and more effecient in the future.
I’ve helped build a couple of small remote cabins like this here in Alaska and they’ve all been the classic cheap cabin with 2×4 walls, fiberglass insulation, Tyvek, and T11 siding. Even though I’m planing on this building becoming a shed within the next five years, I’m thinking I want to spend a little more money and get somewhat “Green” materials and have a proper building.
I’ve done a lot of research on the perfect wall and the science of building an air/water tight building but I’m not sure where to “draw the line” so to speak when it comes to building this cabin ( future shed).
As of now I’m planing on 12in I-joists for the floor and ceiling (16in OC), 2×6 walls (16in OC), R21 rockwool insulation in the wall cavity (and doubling the R21 insulation in floor and ceiling) and regular Zip sheathing (Zip-R isn’t available up here from what I can find). I was also planing on doing an all metal exterior.
One question I have is if I go this route, do I need a vapor barrier on the inside of the wall? As the zip will be installed on the exterior, I am thinking I shouldn’t use a vapor barrier. Hopefully someone can answer this for me!
I’m looking for opinions on the materials I plan on using and weather or not it’s a good combination of materials. Hopefully people with experience can let me know their thoughts and if anyone has any advice they’d like to share I am always fluid with my plans!
Other information to know:
– All materials will be hauled in on a sled pulled by snowmachine
– There are no “codes” or inspections out where I’m at but I want to build something that will be up to code (or at least close to it)
– I plan on having one 10ft door (2 x 5ft shed doors) as this will be used as shed in the future
– I thought about using rockwool comfortboard 80 on the exterior as a thermal break and to add fire resistance to the exterior but after doing the math, It costs to much (with the thought of this turning into a shed in the future) to add the proper amount of exterior insulation needed.
– I’ve lived in small cabins in the interior of alaska before (-60 degrees fahrenheit for a couple of weeks of the year) and all the cabins I lived in we’re insulated poorly. But because of the size of the cabin and the woodstove, I was always on the verge of being “cooked out”. I’m trying build something more efficient where I’m not using as much wood and just have a better performing building all around.
Thanks to all who have taken the time to read this, I appreciate it!
Tyler
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Replies
Tyler,
If you have access to reclaimed rigid foam, it would be great to incorporate it into your design. In any case, you want to focus on air sealing (tape and caulk) to minimize air leakage. That will do a lot to improve comfort and performance over a standard build.
If you end up without any exterior foam, I think you need a deeper rafter. There are design details on GBA, but the experts generally recommend 1.5 to 2 inches above the air permeable insulation. (I'm assuming the shed roof has sufficient pitch to promote ventilation. If it's a low-slope roof, you should consider a different strategy.)
Thanks for the reply! I was planning on a 4/12 pitch (possibly 6/12).
Your talking about promoting ventilation under the metal roofing and above the zip roofing osb right? If not that, are you talking about venting the rafter cavity space?
And the 1.5 to 2in of space above the insulation, so I should have 1-2in of space between the rockwool insulation and the exterior zip sheathing? That's the first I've seen that one but I'll look into that!
Thanks again for the information!
Tyler,
Check out this article: https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work.
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Zip is often used as roof sheathing. I've seen the 1/2" brown version on roofs, so maybe it's the 7/16" green you're thinking of.
That's what I thought, I've seen brown/red zip used on roofs and the green zip (7/16th) on walls as that's all it's rated for. I definitely could be wrong on that as well but I think the thicker zip is rated for the roof.
I corrected my statement on ZIP roof sheathing. Huber apparently changed its product line up at some point.
There's this site for info on building in Alaska.
http://cchrc.org/
And this Youtube channel.
https://www.youtube.com/user/ColdClimateHousing
As for being "cooked out" from using a woodstove in a small cabin, use a wood stove covered in soapstone. This will prevent the stove from blasting out heat for an hour or so and then letting the room get cold overnight.
https://www.stoves-pipes.com/NEO-1-6-SMALL-CONTEMPORARY-WOOD-STOVE-p/neostone-1.6-(ne16.sta).htm
Out of the box thinking if you really will just use this as a shed after the first year: Build a shed and park a trailer inside it that you can live in. Once you build the house, sell the trailer.
I like the idea, only problem is that it's off the road system about 8miles down a pretty rough trail. Everything I'm going to building with will be brought out by snowmachine and sled
Well, on not wasting insulation, exterior foam with interior batt insulation, you can later strip the batts out leaving a modestly insulated shed
But my first thought is really build the house first, to hell with the shed.
Build your 12x24 not as a shed but as half a house. When you are ready, add onto the original
Consider improving the trail into the home site so one can more easily commute in/out before any building begins. You'll experience "burn out" along with putting stress on your personal relationships if the task is too difficult.
Many cabin projects are poorly planned and rotting in the woods in short time. Just go camping!
Not to mention that if the trail is too rough, you'll get really tired of the constant round trips to bring just a few pieces and then the temptation to overload the sled will be too much and then you're bound to lose some materials to damage along the way.
For most builds, 8 miles is a long slog with a pickup truck and paved road to the big box store. Snowmachining over 8 miles of rough trail just to drag a few 2x4s will get old real quick.