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Coast
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# Posted: 31 Jan 2024 01:14am
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I found this site researching design ideas and questions on my new build. What a great source of info, thank you all! I have some questions and am open to suggestions/advice with my project described here.
We bought a property in western Washington with no utilities with the intention to build a cabin in 5-10 years. Until we can build the future cabin, We are planning to build a tiny home on wheels as it doesn't require a permit. I'm not getting a permit because we won't have water or septic for a few years, which are both required for a permit. Structures on wheels don't need a permit in this county, and we are only camping out there a weekend or 2 a month.
My plan is a 10x20 building with an 8 foot back wall and 13 foot front wall with a shed-style roof. There will be a loft in the back 8 feet of the cabin, about 6'6" off the floor, supported by 2x6's 16" OC running the 10' width of the building. Studs will be 2x4 16" OC, roof will be 2x6 24" OC. The building will be dry, no utilities initially, our cooking will be done outside. This will be a place to sleep and to stay out of the rain if necessary. I know 10' won't be road-legal without special permitting, but I will never be taking this trailer off the property, it doesn't need to be road-legal to fit the parameters fo the code definitions for permitting purposes.
The property is 10 miles from the Washington coast and near the rainforest. Snow load will be very light. It's very wet at times of the year.
Some questions:
1. This will be a somewhat tall building for it's footprint, should I be concerned about wind shear or not with the dimensions I've given?
2. Siding: I've built small buildings in a more arid region w/ just T1-11 on studs. I'm thinking this will require a tyvek vapor barrier and am thinking 1/2 plywood on the studs, then tyvek, then T1-11. Am I thinking right on this? I'm also not initially going to insulate the building unless necessary, as the woodstove will likely cook me out w/ insulation and I don't want any extra incentive to mice.
3. Floor insulation: I wasn't planning on insulating, again not too worried about heat and want to keep this simple, but read up on condensation forming under furniture. Found some very conflicting info on reflective insuation like reflectix. Seems like a cheap and easy option to put on the joists under the subfloor that doesn't have any real downside and might help keep critters at bay. What are peoples experience with this? Enough to keep condensation at bay?
That's it for now, but plan on adding updates and questions as they come up in our build over the next year. Thank you!
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909
Member
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# Posted: 31 Jan 2024 09:36am - Edited by: 909
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1. I used 2 x 6 x 12' on the front wall and 2 x 6 x 10' on the back wall. Roof spans 10 feet. 16 foot rafters. Shed roof overhangs about 34 inches all around. 5/8 ply sheathing. Hurricane ties at everywhere. Metal roof. Snow slides right off.
2. I used vapor barrier inside. Acoustic sealant and blue tuck taped the seams. R24 on the 2 x 6 walls. 1/2 ply exterior sheathing. Housewrap with red tuck tape on the seams. Butyl flashed the windows and doors. Cultured stone siding. Mice don't like rockwool. With so many siding options, some of the premium wood or composite siding costs almost as much as stone. Metal is a very inexpensive and popular option here, but it will get dirty ( think of how a car would look if it never got washed ). It dents easily. And metal also blocks cell signal. The siding you decide on will depend on your budget and personal style.
3. I used 2 x 10 PT for floor joists and insulated with R24 in the bays. 3/4 SPF ply ontop . And 1/2 PT ply underneath. In hindsight, I wish I installed more insulation. Doesn't matter how warm you get your cabin, if you have a cold floor you'll feel it right in your bones. Nothing beats a warm floor.
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gcrank1
Member
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# Posted: 31 Jan 2024 10:48am
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Over the road width here is under 14' iirc needs no special permitting, but a building that large/heavy you don't want to be hauling (the frame and axles would need to be huge). I heard about a guy who did as you propose and just bolted a salvage single trailer axle/wheels under his floor beams, lol.
Funny how a 'temp' cabin turns into 'more'.....
Build like you mean it, not like cheap shed. The amount of work will be similar but materials more, but the satisfaction will be more too.
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DaveBell
Moderator
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# Posted: 31 Jan 2024 10:52pm
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Quoting: Coast There will be a loft in the back 8 feet of the cabin, about 6'6" off the floor, supported by 2x6's 16" OC running the 10' width of the building.
Show me what the IBC code says about the live load on 2x6's 16" OC running the 10' width. Each joist should supported underneath by its own added
wall stud to the floor. Nailed to existing wall studs. Do not depend on the wall studs by themselves holding up the loft.
Quoting: Coast should I be concerned about wind shear
Quoting: Coast thinking 1/2 plywood on the studs, then tyvek, then T1-11
Yes, Then paint two coats on the T1-11.
Mice. Three of them got into my RV and pee'd and pooped everywhere. The smell made the RV trash. Build some wood boxes 12"x12"x4" (maybe four for one on each side underneath) and buy the peanut butter scented glue traps from Amazon. Drill holes on each side box for entry. 34 mice later, my RV is headed to the dump some day.
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DaveBell
Moderator
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# Posted: 31 Jan 2024 11:04pm
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Don't forget drip edge for the roof. My shelter roof, 2x10's 12 foot long, 16" OC, birds mouth cuts resting on 2x12s with H-1 Hurricane ties, 1 foot overhang, 5/8 plywood, felt underlayment, low side drip edge, metal roof panels with metal screws - rubber washers not crushed, silicone caulk sealing metal sheets to each other, then high side drip edge.
The code provides minimums, nothing wrong with over building.
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Coast
Member
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# Posted: 1 Feb 2024 01:37am
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Thanks 909, was looking at using hurricane ties to be safe, glad to get some input affirming that. I've never used house wrap before, so just read up on tuck tape based on your comments, makes sense, thank you for that. Appreciate the advice on warm floors.
DaveBell, I tried looking up the IBC code on 2x6 live loads and only found info that seems to show a 10 foot span will be fine, based on how I'm reading it, but I'm not confident I'm understanding what you're getting at. Studs under the joists makes sense and was my plan to be safe, so good to get feedback on that.
I didn't have a plan for drip edges, but do now. Thank you.
I really appreciate the advice and tips so far, shows that you don't know what you don't know! But that's what I was hoping to get out of this, so thank you very much. Keep it coming!
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Brettny
Member
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# Posted: 1 Feb 2024 05:50am
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They make simpson 6 or 8in screws that are cheaper than hurricane ties and do the same thing. There also way quicker to install. You basicly just screw a 6 or 8in screw diagonally into the top plate into the birds mouth.
You dont need to put plywood down under a metal roof. Most pannels are rated for perlins every 2'. I would use a proper metal roof underlayment, tar paper isnt.
Also T1-11 is sheething so you can put it right on the studs. No need for two layers of sheething. You can still put house wrap over the studs prior to the t1-11.
What are you doing for windows? If you can get new construction windows with a nailing flange and J channel. It allows you more area to properly weather seal. This can be prety important with a 13' tall wall.
I would also put every board together thinking about how a mouse could or would get in. They almost always find a way so minimize any gaps or cracks in the building phase can really help. They CAN climb rough siding like t1-11.
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909
Member
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# Posted: 1 Feb 2024 09:52am - Edited by: 909
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I wanted to thank Dave for mentioning to silicone the roof panel seams.
And for the mousetrap idea, one under each corner of the house.
Wrapping house wrap alone can be very difficult, and challenging without a second pair of hands.
I used wood scraps (screwed together in an L shape, with an adjustable shim) to lift, pinch and hold the housewrap (while you walk away adjust ).
I did a continous wrap all around with as few seams as possible.
Please be careful. You'll be 14 feet high in the air. Working off a ladder. Holding a heavy roll of house wrap. Building on raw land, we often work on questionable soil, with poor footing, and alone.
Always wrap from the bottom up, and overlap.
Please wrap it as tight as possible.
Wind is your worst enemy.
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Brettny
Member
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# Posted: 1 Feb 2024 09:56am
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You could also put the house wrap on prior to standing up the wall.
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gcrank1
Member
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# Posted: 1 Feb 2024 10:15am - Edited by: gcrank1
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On my first build in '83-'84 I used a modified post & beam construction with cdx plywood sheathing, then 1" blue DOW styro, then my barnyard siding (didn't know about housewrap then or I would have probably used it.
I had not intended to insulate the inside walls and liked the post & beam look. If I had stud walls I probably would have still done the styro and used batts as normal too (as time went on, a wall at a time).
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ICC
Member
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# Posted: 1 Feb 2024 01:32pm
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Quoting: Coast , I tried looking up the IBC code
If you are building a one or two family residence, including a part time use cabin, refer to the IRC in most states (not WI). IRC is simpler as the IBC also covers commercial properties.
For spans there are IRC tables or you can use the AWC span calculator. Google can find that as a web page or an app
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DaveBell
Moderator
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# Posted: 1 Feb 2024 05:48pm
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Thanks ICC, no wonder why I couldn't find the tables.
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Coast
Member
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# Posted: 3 Feb 2024 10:31pm
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What are thoughts on making the back short wall 8 ft for standard plywood sheathing vs 8' 4.5" or 9 foot for a taller dimension loft? 8 ft is obviously cheaper materials and less cuts, but will the head height up top in the loft be worth it when all is said and done? I'm trying to remember this is the 5 year plan before the final build.
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MJH
Member
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# Posted: 3 Feb 2024 11:51pm
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Quoting: Coast What are thoughts on making the back short wall 8 ft for standard plywood sheathing vs 8' 4.5" or 9 foot for a taller dimension loft? 8
Not exactly sure how you are planning to build but if you are using traditional floor joists and are trying to get by with one 8 foot sheet in the back you will have to likely go shorter than 8 feet. Covering the rim joist with the plywood will make things much stronger and also more protected.
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