Large Foamy

[loaderman]

I am interested in building a mobile guest house. And have been thinking about styrofoam walls and came on this.

Any one built 7&1/2' walls?

Say 2 layers of 1" foam overlapping seems. Canvas on th outside and 1/8" hardboard on inside? or something better?

Looking at 8.5' wide and about 24-30' long

[GPW]

Loaderman , while that’s BIGGER than any of have thought of , it seems entirely possible with the correct framing inside ... Seems it might require some Engineering to pull it off ... Interesting thought ...

[atahoekid]

I agree... Good thought on the overlapping seams, should give it a bit more strength. I'd have to say a bit of framing would be required and with an area that large, the wind load and a snow load (if that applies) might need to be figured in... I'd say it certainly is worth looking into the idea and weighing it against more conventional methods. Doubt that you could get it to pass a code inspection though. Those folks seem to have no imagination and if it ain't in their book, it doesn't pass, irregardless of what common sense, logic and empirical evidence shows. Ask me how I know!

[linuxmanxxx]

I had posted on the big thread previously that I was planning on using 3/4" doing the overlap to make my walls. Use the 3/4" instead of the 1/2" and then you only need to place a single 1x2" runner vertical between the sheets on the inside for strengthening and stiffening the walls and when you do put the inner plywood up make sure you lay a line of tigtbond3 on the 1x2 runners and I'd recommend the 30NF contact cement for the foam to plywood and you'd have some seriously strong light walls and just keep going to the 8 to 9 inner panels wide would give you the size you want. That big every inner wall you build will also add to the strength of the overall structure and you could just use normal single 3/4" sheets for the inner walls with the thinnest panelling/luan you can find on both sides would be very strong for supporting the roof structure. I like the idea sounds cool as heck and pretty much what I had planned but not near as big.

[loaderman]

Thanks,

Yeah a full foamie probably to hard.
Maybe 1&1/4 by 2" studs every 4 feet on the joints of the interior paneling then 3/4" by 2" studs at the 2' mark.

Inside use 1/8" panelling, on outside use canvas and tb2?

do an arched roof side to side with rafters every 2' lined up with studs. Maybe a bow truss and 3" styro (3-1") on top. But I would like the ceiling inside to curve for more headroom and only do 7' walls. How could I make those rafters/truss?

[Rusty O'Toole]

There is a factory near here that builds prefab warehouses etc. out of corrugated sheet steel bonded to 6" styrofoam and that is it, that is the wall. Fastened to a structural steel frame.

For a project like yours the simplest and cheapest way would be wood paneling on the inside, 2" of styrofoam, Masonite on the outside.

Masonite will last 10 to 20 years if kept painted. There are some Masonite sided trailers built in the 30s still in good condition, but were stored indoors or under shelter when not in use.

Next cheapest, paneling/foam/chipboard or plywood, with some kind of siding, vinyl siding like a house, aluminum or plastic siding like a trailer.

2" thick foam core walls would be plenty strong for your use. Include some 2X2 spruce where you want to put doors and windows or where you want to fasten anything to the walls such as a partition or cupboards.

Make a test piece of styrofoam with paneling or masonite or chipboard on both sides. Lay it on a couple of saw horses and stand on it, you will be amazed how strong it is.

This is basically the same idea as the Mosquito bomber of WW2. 2 Merlin V12 2000 HP engines on a fusilage made of 1" of balsa wood with 1/4" plywood on both sides. Unbelievably strong, they had the best record of any bomber of bringing their crew home alive.

[mezmo]

Hi Loaderman,

It sounds like you're looking to build a 'Tiny House' style unit.

Since Foamies are in their developmental stages here, we have to look
everywhere for ideas and 'direction'/inspiration. A unit as large as you are
proposing will definitely be a first here and you'll will need to consider many
areas for it's structural integrity and longevity. I'm not going to enumerate
them all as they will arise as you begin planning in earnest.

I just want to mention that your proposed build is very doable.

Also, look into SIPs [Structural Insulated Panels] for ideas and techniques
that you may be able to use for the build. What you, and others so far,
are proposing is basically a thinner version of them.

I would advocate you do a thicker wall though - say 2in - for such a large
body. It will be stiffer and provide more insulation factor and be easier
to work on. Also I'd advocate you do a perimeter panel frame as well as
internal perimeter frames around all openings. I'd even go for 1/4 ply
inside and out. A bit heavier true, bit still easier to work with, and it is a
guesthouse, so total weight isn't as high of a concern as it would be for
a unit meant to travel all the time. And use the 3M contact cement that
liniuxmanxxx mentioned to glue them together. The perimeter panel
framing will allow easier attachment of the panels to each other. The
opening's perimeter framing will allow easier installation of windows and
doors etc.. The exterior can still be covered in fabric and glue/paint/etc.
for waterproofing and then painted and so on.

I'd also suggest to try and make the components "modular". I wouldn't
make the design necessarily fit a module, but rather get your design
finalized, then 'modularize' it - i.e. do wall panels in 4ft x7ft modules or
smaller [as you want 7ft tall side walls], with smaller 'one off' sizes as
needed. They'd be about as large as you'd want to attempt to handle
alone. [A lot depends on your accommodations - or lack of - for building
too.] There are numerous ways to join the panels together, the most
common would be some sort of tongue and groove effect to do so

Remember, the first Winnebago motorhomes and TTs used a
"Thermopanel" construction, which was internal paneling, structural foam,
and exterior aluminum. They were very successful. What you are
proposing is very similar to that.

Since you want a curved/bow roof and asked for suggestions, let me
refer you to the Foamstream thread in the Foamie section here:

http://tnttt.com/viewto ... foamstream

Your guesthouse is basically just a little larger version of GPW's
Foamstream proposed build. There are a lot of ideas and discussion that
would be relevant to your build there.

On page 4, I made a long post giving suggestions for ways to form a
curved roof section by lamination of 1/4in plywood 'strips' into arched
framing members etc., so I won't go into the details here, just go to pg 4
of the thread to see if any of that would interest you.

It'll be interesting to watch your progress once you commence the build.

Cheers,
Norm/mezmo

P.S.: I see while I was composing my post, Rusty O'Toole posted info
quite similar to mine - let''s call it the old joke of 'great minds thinking
alike!' - Ha!

[linuxmanxxx]

I honestly think if you do a half sheet overlap of the 3/4" and a full 1x2 from top to bottom for stiffness you can make it work no problem since you'll have it fully skinned on the inside with a panelling and fully glued would make the wall rather stiff before you put the canvas on the outside. That would make the overall thickness 1 1/2" and make it plenty insulated and then you just need to come up with a plan to make the roof strong enough to hold up under some weight load and best would be to do a slight center peak sloping to the outsides like a normal house uses same double 3/4" with the inner runners spaced half sheet laps. I build single 3/4" sandwich walls in my camper and can walk on the roof so I think the double 3/4" and the 1x2 for strength would be well more than enough to give the structure strength and stability and the inner walls like I stated before just make it stronger yet and still keep the weight down.

[loaderman]

UUUUUUUUUUHHHHHHH, so many possibilities and questions.

Ok so thinking about floorplan, trailer design, building it economical.

Is it best to put it all in this thread or make other threads for each part?
In some ways easier to follow in separate threads but as one thing affects another it might be better to keep it all here.

Ok so some criteria.
1. Economical to build
2. easy to build
3. Light weight but strong, Floor plan is still being ironed out 22-28 feet long about 7.5' high inside, 8.5' wide. Do not want it to collapse but want it light, would love to tow behind 1/2 ton. Not moving it often, but in future could move it 4 times a year for 12 hour drive at 60mph (100km/hr)
4. Look decent. neighbours not complain, the wife has to like it.

[loaderman]

Back to the walls & roof.

For the walls I need to be able to live in in winter.
My house is r12fiberglass. Gets to -30c in the winter for a week or two. above +30c in the summer.

is 1.5" styro at r 7.5 enough? If it is continuous it would be better then fiberglass and cold transfer through studs and fiberglass not always installed perfectly.

Thinking using 1.5" styro with a 1x2 stud every 4'.Wood is 4x strong if you double its depth rather than width, so the1.5" dimension is 4 times strong then the 3.4" dimension so it would be stronger to put it like a stud in a wall then on the flat. Also 1x2 bottom plate. Then outsdie of that put 3/4 styro. Gives 2.25" of styro a R11 rating. also with the continuous 3/4" layer less cold transfer through studs.

Paneling or hardboard on the inside and just canvas on outside?

How to tie in the roof? Build it arched, or like a usual roof on a house? Flat on the ceiling or arched or cathedral depending on the top shape? Want it light but strong, and easy to build. If build arched or cathedral ceiling could go with lower walls.

Thinking leaving studs say 3.5" down from the top of the walls, or extending walls 3.5" above 1x2 - whatever. This would allow a notch for the rafter which would be every 4' to sit down in. the styro on the sides of it would add lateral support. use 2 layers of 3/8 ply and cut arch 3.5" high. put panel on bottom of arch (ceiling) and fill with Styrofoam, then 1/8" panel ton top and canvas and paint over that.

Not asking for much am I

[loaderman]

ON the rafters. I sure wish I could get 10' 3/4 plywood, Since I can not I will use 2 layer of 3/8 and stagger joints. if 3&1/2 not enough I could add a layer of tin between the two 3/8 layers. Doesn't need to be thick to add a lot.

We have done this with beams in basements when moving teleposts. It is amazing what say even less than 1/16th thick tim/metal will hold when held ridged between two 2x10's.

Think of a empty soda can, because it is curved and stays upright. even though it is thin it holds up a man standing on it until you flick the side and dent it slightly then it crumples. Kinda the principla behind the new engineered I-joists for floors.

[vwbeamer]

The question is, are there any bears near by?

[loaderman]

Yep, had them in my yard in town before I put up the fence!

[GPW]

I’d go for as many Rs as I could get ...

" the wife has to like it.â€

[loaderman]

What does styro (the blue sm or the pink celfort) weigh?