What fasteners should I use with Tyvek

Is it okay not to have a vapor barrier in the lightweight construction of a tiny house?

So I have a strange project. It's a little out of the box and I'm looking for alternative approaches that stick to the subject (if the plan outlined below doesn't work, that is).

Essentially, I'm building a mobile home, but I'm thinking of "tiny house". It is built on a 17-21 foot camper frame. The difference is that I try very hard to keep it as light as possible for two reasons:

  1. Camper frames are not designed for the heavy weight that a true Tiny Home construction requires.
  2. This needs to be easy enough for it to make sense to sign up for a weekend getaway. "Tiny Homes" give the scales far beyond what is reasonable.

I want to keep the "cabin" look even with a natural looking siding. I also try to keep it as simple as possible. More like an ice cream parlor that may never see real ice cream and is more likely to be used as a sleeping house. It is heated, cooled, etc. and sometimes not parked.

For the walls:
2x3 studs are used to frame maybe 2 'off center and rigid insulation is used to fill in the gaps. Outwardly is mine idea to use a skin siding that looks something like T&G. There's a product at lowes that matches the bill. This provides both sheathing and siding in one layer.

I would use a combination of 2 "and 0.5" layers of insulation to completely fill in the 2.5 "depth created by the studs. Some type of glue would be used liberally to bond the layers of insulation together, to the studs, and the siding Decorative interior trim (something thin and light, like 1/4 "siding) would be used and also applied with generous amounts of glue.

So it's like creating a large DIY SIP panel that includes the frame, siding, and interior trim. The purpose of all of this is to lower the materials needed and keep the weight down, but keep it very strong by joining all of the layers together. After all, it will be the forces that appear on the highway.

After all that, I am sure that I am naive on many aspects - about a vapor barrier, for example. My basic understanding of Tyvek is that steam can pass through it, but moisture cannot.

I won't have a jacket to put in a vapor barrier as the jacket and siding are one layer. Is this a terrible idea and are there any alternative approaches?

Installing windows is another problem.

Bottom line: I don't want to build what will be a rotting, moldy box in a year.

BrownRedHawk

Just one comment on the choice of fastening, many adhesives can far outweigh mechanical fasteners. I would suggest a combination of the two to get the right rigidity, surface contact, and mechanical clamping.

bib

Big problem with shelves, both front to back and side to side. The hoop construction is not really well suited for this.

mfarver

It may be worth noting that most recreational campers are already built this way. The sides of the vehicle are made from just a single layer of 1 "XPS foam, with some 1" square tube metal ribs in strategic locations for strength and rigidity. The inner lining and the outer skin are glued to the foam and steel ribs with full-surface adhesive.

iLikeDirt

Haven't you asked the same question elsewhere recently? That sounds very familiar to me.

You should stick to proven wall designs. 2x3s will be more difficult to work on. No sheathing means practically no resistance to wind. You almost never want a dedicated vapor barrier, especially if you plan on using rigid foam somewhere (this will result in a steam trap). Your plan with no outside sheathing is risky if you don't plan to put house wrapping or tar paper underneath.

If you really want to do this, here would be my inside-out recommendation:

  • Light wood paneling or whatever
  • 2x3s for structural framing with cavities filled with lightly compressed fiberglass or mineral wool mats ( Well Installed)
  • Diagonal steel struts for abrasion resistance
  • 1+ "foil-coated, non-structural foam wrap (use Polyiso if you live where it's hot; otherwise EPS) over the outside of the cleats to act as a thermal break. Resistive barrier layer
  • 1x3 or 1/2 "strips of plywood attached through the foam and into the studs to act as vertical strips of fur
  • Siding attached to the fur strip

This gives you a safe, compact and energy efficient wall.

Last thought: if you want a weekend camper, this is the one to buy. It will likely cost you a lot less money than doing all of this yourself.

slambeth

No, I haven't asked that anywhere else. although I'm sure that kind of question comes up a lot. Thank you for submitting, I'll look into suggested materials. I assumed the "go buy a motorhome" suggestion would come up. I have certain things I want to do with this project - and most of the campers from what I see are complete junk anyway, even the new ones. That's only $ 30,000 of total junk. I'll have fun building it too.

Ecnerwal

Skip the 2x3 studs. If you build "fast SIPs" you will get a better (lighter, stronger, better insulated) product by just building (or buying) SIPs and building using SIP methods. Modern construction adhesives make this a far more practical DIY project than they used to be, although it shouldn't be all that difficult or expensive to factory build.

Or get a used refrigerated truck body made of steel, fiberglass or aluminum SIPs and already built for highway speeds. Learn fine art painting in the time and with the money you save and people have to go right into it to see if it is boards or not.

slambeth

Maybe I'll simplify this and use 11/32 sheathing so I can put house wrapping on top, and then any siding I want (maybe T&G cedar). It will likely add 500-600 pounds to the walls, but it sounds like it simplifies things a bit and is worth it.