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Small Cabin Forum / Cabin Construction / Need some help on 8x28 build
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Goatboy
Member
# Posted: 25 Feb 2014 18:30
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Hey there,

Long time listener, first time caller.

I'm looking for some advise on a fairly unique build I am doing.

I own some land but zoning is preventing me from building any more homes with a foundation. having a trailer parked on the land is fine. No building inspectors or anything like that where I live.

Buying a new trailer bed is in the $6000+ price range. I'm planing to build on top of a trailer bed that previously had a mobile home on it on this property. I demo'ed the mobile and roof that was built over/on-top of the mobile. The trailers tires are toast and I'm not able to move the trailer anyways. My water/power/septic is already in place to the trailer location, which is another reason i'm building on this spot. The trailer is in good shape I just need to nock off some surface rust and re-paint it. The main of the trailer is 2 steel C beams with 8 smaller cross sections tying it together. Not sure what the weight rating is (6-8000 maybe) but I would imagine that is for the tires and suspension only, not the frame.

Here is what I have so far.

The home is going to be 28x8 w/14x8 loft. About 12ft from trailer bed to peak with a shed style roof. I'm going to tie in the house to the trailer and I have some tiny home plans that I purchased and modified by lengthening and moving some windows around.

So I guess i'm looking for some input on how the best way to build on the trailer as a foundation would be?

My current plan is to do a sub floor with 6" joists @ 24" apart, crossing the C beams and with an overhang of 18" on either side. the spacing between the beams is 60". 2x4 framing and a metal roof. I would prefer to have a foundation of just concrete blocks supporting the beams which is what the previous owner did when it was a mobile home but i'm not sure if the 18" overhang is too much? should I double up the joists to give greater support to the over hanging walls?

Hope this all makes sense, obviously i'm a noobie so I apologize for my ignorance ahead of time.

Any input is very much appreciated.

ps. most tiny homes on trailers are smaller with a different style trailer bed and meant to be moved periodically. Otherwise I could just follow a classic tiny home build.

-Goatboy
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bldginsp
Member
# Posted: 25 Feb 2014 20:00 - Edited by: bldginsp
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I fiddled with such mobile home trailers for a while, I'm no expert, but here goes-

Supporting them on concrete blocks with 2x wood between the blocks is standard, the more you put in the better for long term stability I suppose. The blocks go under the long beams as you showed, and then the walls are supported entirely by the cantilevered steel arms welded to the frame, in standard mobiles. But, the walls were usually 2x2s with aluminum skins, and 1/4" plywood inside, and the roofs were pretty light too. So point is I would not support your 2x4 walls and heavier roof on the steel outriggers alone. Your idea to cantilever 2x6s is a good one, and if you also land the rim joist on the steel outriggers I'd say you have plenty of support for whatever you build on it. If you want extra insurance you could use 2x8 for the joists, but its probably overkill.

I'd put block supports every 4 feet or so, because you are making one heavy unit, and it has to handle snow load. If you have a lot of snow maybe the 2x8 floor joists is not such a bad idea. Mobiles were not designed to take any snow at all, just their own flimsy walls and roof.

If you can, getting some basic calcs on this might be very revealing. Figure total wall and roof and snow load and get a cantilever calc on 2x6 and 2x8. You have no way to get a calc on the load capacity of the steel outriggers unless your 3d cousin is a steel engineer. Then, calc total building weight with max snow and figure how much area of dirt you need to cover with the blocks, given a minimum soil bearing capacity. Got your work cut out for you, but remember you are building a very heavy building with snow on a frame and blocks that probably took 1/4 the weight before.

Next step would be to provide support directly under the walls, but then you are leaving 'trailer repair' land and entering 'cabin construction land' if you catch my drift.

Goatboy
Member
# Posted: 25 Feb 2014 22:51 - Edited by: Goatboy
Reply 


Thanks for the reply bldginsp, I really appreciate you taking the time.

The snow is a very rare thing around these parts and it rarely accumulates for more then a few days when it does snow. That being said I should probably prepare for a just incase scenario. Im also planing to build as light as possible as far as materials go.

I guess it would be smart to do some calculations before i start building haha.

I was surprised when I was peeling the floor joists that they where all running along the beams instead of across them. Ya the walls were supported entirely by the outriggers and the previous owner had built an additional roof with 2x6s and 2 layers of shingles all resting directly on the trailer top. its amazing the 2x2's and outriggers held up.

thanks again, I will post updates and pictures once I start building in a few weeks.

bldginsp
Member
# Posted: 25 Feb 2014 23:29
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Interesting idea from the perspective of building without permits. So long as you leave the axles and wheels, it's a mobile which is not covered by the building codes, but rather by other state agencies, and will they find out or care? Would a building department try or be able to stop you? So, theoretically, you could build a nice new building with no permits. Of course, you are limited to the dimensions of the trailer, and 8 feet wide feels like a sardine can after a while, but for temp use that's not so bad. And, of course, you have to find a trailer for cheap and be willing to rip it and dispose of the old structure. Hmmmmm... Is there a trailer in my future?

Goatboy
Member
# Posted: 25 Feb 2014 23:58
Reply 


Ya some ups and downs to doing things this way but for me it makes sense.

Also i'm putting a minimal amount of cash in so as long as its safe, and i'm debt-free then i'm happy.

I actually like the idea of having a very limited space to live in. Lots to do outside during the day. All I really need is a comfortable roof over my head at night.

I will post a lay-out and plans in a few days to give a better idea of what i'm looking to do.

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