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Suggestions for utilizing upright tube framing of trailer

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posted 4 years ago

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Hi there,
I am looking for general suggestions on how to be utilize a trailer that has existing steel framing on the walls. The tube frames are 2″x2″ and the height from ground to the ceiling is 130.5″ (therefore the walls are 8′ tall). Here is a link to an image of the trailer:

https://ibb.co/8msxHb3

I would like to cut out at least some of the front wall and turn the gooseneck landing into a bedroom.

What I am unsure of is how to best insulate and frame the house. Should I attach 2x4s to the steel frame? Should I remove the ceiling entirely? Any suggestions are much appreciated.
Thanks

William Bronson

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posted 4 years ago

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Cool project!
Is this intended to be mobile or sedentary?
Does the existing roof leak?
Did the walls?

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Tay Ob

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Hi William,
For the most part sedentary, though I expect to move it once it is built to a location where I can live for an extended period of time.
I haven't gotten my hands on it yet, but I don't think there are any issues with the roof. As for the walls, the trailer originally came without walls attached to the frame.
Thanks!

William Bronson

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posted 4 years ago

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If you are going to have a loft, reinforcing the walls will be important.
I might add two by material in between the existing steel members, for more places to screw things to.
I think I would be inclined to add a peaked roof over the existing roof.

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John C Daley

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posted 4 years ago

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Assuming there will be no loft;
- use existing ceiling as a liner for the house.
- Add a structure on top which you can insulate using the ceiling as the bottom.
- If you are not going to take it on roads, I suggest installing cool room panels on the outside of the frame as the weather proof and insulating segment.

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D Nikolls

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The current and desired outside width and height will be a huge factor.

What are those dimensions now?

What are you aiming for? Max legal size for a private owner, or for a commercial tow company without a pilot car, or some greater specific oversize dimension?

I built mine max legal road size for me to tow, 8.5wx13.5h. I'd go for commercial width and an overheight permit if I was doing it again...

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Eliot Mason

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Tay: As others have indicated, the final allowed width of this is critical, as is the current width.

The 2x2 steel is a problem for interior walls ... not only is a 2" cavity thin on insulation potential, but its also really hard to run any electrical in there (well, the electrical runs are do-able, but you'll be really limited on electrical boxes ... and if they do fit there will be almost no insulation behind them. so you might be lookin at furring strips on the inside or outside to increase your wall cavity.

Since steel is a nearly perfect thermal bridge (at least in comparison to wood!) I suggest adding a a layer of insulation on the outside - if possible.

I'll second the suggestions to have a pitched roof - a flat roof is a future leak, and doesn't have much insulation potential.

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Tay Ob

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posted 4 years ago

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Thank you for the suggestions!

There won't be a loft above the main deck; I plan to knock down part of the front wall and build stairs to a bedroom above the gooseneck.

The current height (ground to roof) is 130.5" and the limit is 160". The current width is 93" and the limit is 102". So I will be going for the max legal size for a private owner.

I am thinking of cutting out the existing roof entirely and framing a pitched roof instead. With sheathing, siding, roof overhang, and gutters, I should be getting close to the width limit. By cutting out the existing roof, My ceiling height will be extended a bit, which would otherwise start to become limited due to adding the floor framing, etc.

To give more room for insulation and make it easier to attach the sheathing, etc., I plan to attach 2x4s to the existing metal frames. I like the idea of not having to worry as much about the structural integrity by using the existing frame, but I am open to ideas.

How does this sound?

Thanks again!

Eliot Mason

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posted 4 years ago

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Tay - hard to tell much about the existing structure from the one photo. It looks like that is not just a commercial trailer as there is a doorway framed in ... and commercial trailers don't have that much support in them anyway.

A simple question ... why keep any of it? Its better to have a unitary structure than one cobbled together. It seems you plan to have floor framing ... so extend the floor framing outboard and place your walls on that. If you replace the whole roof assembly with a pitched roof you'll be extending the wall structure vertically, but its better to have all those loads just come down in compression instead of into shear where you attach to the existing steel tube. Building a 2x4 wall is really no more difficult or expensive than adding furring strips to all that steel - and you'll have complete freedom to place windows and doors.

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Tay Ob

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posted 4 years ago

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Thanks Eliot!

Yes, that is the alternative; remove the upright structure all together and just frame from scratch. I'm definitely interested in hearing other opinions on this!

For additional stability, perhaps I can leave a few metal uprights where I am confident they will not interfere with any windows, etc?

Another question I have is regarding the gooseneck platform. Most gooseneck trailers that are built specifically for tiny homes seem to have a rectangular steel platform on the gooseneck, but as you can see from the photo, there is only the triangular metal frame there. Is it ok to frame a floor directly onto this if I bolt it directly to the steel frame and attach it to the wall framing from the rest of the house? or do I need to weld a steel platform down first?

Thanks again!

John C Daley

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posted 4 years ago

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I dont like redoing things.
If you add 4 inches of coolroom panels to the existing frame, you will have width of 101".
And that material does have metal coated both sides.

Windows etc can be installed within the existing structure and very quickly your walls would be complete.

D Nikolls

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I don't like redoing things either... but I also don't like walls that don't breathe, though the coolroom panels would be quick!

It's hard to tell how robust that framework is from here, but seems a shame to remove if its in decent shape..

Plus, the width is a great fit for external insulation. Which happens to be a great way to get better whole wall insulative values in the same thickness..

I would use rockwool, it comes in panels for this application, not the batts for inside walls. Sheets of this over WRB over plywood, then furring strips for a rainscreen gap, then steel siding.

On the inside of the ply is the structural part; the current steel plus any reinforcements needed... with additional insulation and your vapour retarder on the inside of all that. All assuming a cold climate...

Yes to welded steel support for the gooseneck platform, otherwise the floor joists up there will need to be pretty big to handle the cantilever... eating up precious height and adding weight... no, I don't know how big is big enough..

Tay Ob

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posted 4 years ago

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Thanks Nikolis!

I finally got to see trailer in person and the steel framing seems pretty sturdy; I may just have to do some rust removal and put on a fresh protective coating. I also measured the width of the trailer and the whole width is 96" (it was 93" inside of the framing). This may change your opinion on the insulation.

Can you send a link for the type of rockwool panels that you are referring to please? Are you suggesting putting it on the outside of the metal framing? How does the sheathing/siding attach to this? Sorry, I am a bit unsure of the ordering of materials you suggested from the inside out.

I am on Vancouver Island, so it is a relatively cold climate, and moisture is definitely an issue. What will I need to do in order to prevent, say, condensation on the metal from affecting the other materials?

I would also like to have a wood siding and plenty of windows. Is this possible with the method you suggested?

Thanks again.

R Scott

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posted 4 years ago

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Triple axle, so it's probably a 25,000 lb 12,000kg rated trailer. Doesn't look that long, 25 foot deck? But pictures are deceiving.

Good thing about a deckover is a completely flat floor, no wheel wells to deal with. Bad thing is the deck starts a foot and a half taller, taking away interior height.

There is a LOT of room under the deck of that trailer, plenty to insulate and put mechanicals.

Easy to add a deck to the tongue, but be careful not to go too wide. I wouldn't make it square, but a taper to 5ish foot wide at the front. Otherwise it hits the back window of the truck when it turns. Leave more space if you want to park in remote areas for turning on a hill, or make it bigger if you know you have a special extra long tow vehicle. You probably could use the extra wall framing metal to build it.

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R Scott

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posted 4 years ago

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For reference, the gooseneck ball to window is three feet on my truck, a short bed. A long bed has another 8 inches or so. To get more room, you would need a 4500 with a 10-12 foot flatbed, but you have to be careful because many 10 footers have the same wheelbase as a standard long bed, all the extra length goes behind the axle.

Many campers are very deceptive in their loft. They "look" square but the bottom is rounded back so it has clearance low but the top juts out above the cab in a tight turn. A sort of prow made to not look like one.

Tay Ob

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posted 4 years ago

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Thanks Scott! I wouldn't have thought of that.

Tay Ob

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So my current plan is to keep the existing steel framing on the walls, yet cut out the roof and build a pitched roof with lumber. I am think I will use 2x4 studs in amongst the steel wall framing in order to frame in windows and a door as well as provide some additional room for rockwool insulation. This will allow me to easily attach the sheathing to the outside and also attach interior wood to the inside. However, my main concern with using the steel framing is the moisture that will collect on the metal due to condensation. This will be in direct contact with the sheathing and some of the framing, which would likely result in rotting relatively quickly. Does anyone have some suggestions on how to prevent this? Can I wrap the metal in something? Thanks!

Tay Ob

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Part of what I am debating is whether it is better to (1) insulate the steel and have it on the interior side of the framing or (2) have it on the exterior part of framing to prevent any contact between the interior walls and the metal. (1) has the advantage of reducing the cold air in contact with the metal, which reduces the chances of condensation, however, the bottom of the steel frame will still be in contact with the cold air since this part of the trailer will be exposed. On the other hand, (2) won't allow the inevitable condensation from contacting the warmer wood on the interior walls; is having condensation in contact with the sheathing an issue?

I'm not sure which one is better? or if it is just safer to remove the steel all together?

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