Plywood thickness

[Irving]

What thickness of plywood have you used for the interior as well as exterior walls of your build? If you have insulated - what thickness insulation foam board have you used?

After exploring the idea of a "foamie" build I am blown away that you can build almost the whole thing out of foam board and have it be structurally sound.

I am considering the idea of using just 7/32" plywood for both the interior and exterior walls and putting 1.5" foam insulation in the middle. This is a huge departure from my original plan of using 1/2" plywood on the interior and exterior.

[Woodbutcher]

The one trailer I built that was completely insulated I used 1" foam between 2 , 1/4" sides. There was a stick built frame as well. Not a foamie.

[Irving]

The one trailer I built that was completely insulated I used 1" foam between 2 , 1/4" sides. There was a stick built frame as well. Not a foamie.

What do you mean by "stick built frame"?

[OuttaHand]

Mine is 3/4" exterior ply, 3/4" foam insulation, with 1/4" plywood on the interior.

[Woodbutcher]

The one trailer I built that was completely insulated I used 1" foam between 2 , 1/4" sides. There was a stick built frame as well. Not a foamie.

What do you mean by "stick built frame"?

[Gage]

I build my teardrops with 1/2" outside ply (main wall), 3/4" foam then 1/8" inside ply. That's what works for me

[Bigblock352]

I'm using 1/2 ply with cut outs with 1/2 foam in the cut outs for the main wall with 5 mil outside and 1/8 inside.

[Vindi_andy]

Mine is similar to woodbutchers 1/4" in and out with 1" insulation between and simple stick frame. Had even less sticks then wood butcthers. 1 either side of door and window running top to bottm and one where the galley bulkhead will be. Just enough to join the 2 faces together. Still pretty heavy things.

[dwgriff1]

1/8 almost everywhere.

[Irving]

So I am building my walls with 1.5" foam insulation and 1/8" hard fiberboard on the inside and most likely 1/4" OSB (chip board) on the outside. I am going to be covering the entire outside and bottom with canvas and tightbond 3.

I'm still a bit hung up on using the OSB board. I almost bought a bunch of 11/32" plywood but decided it was too heavy and put it back.

Should I be talked out of using 1/4" OSB board? Any good reasons not to use it? It is just so cheap at $9.50 for a 4x8 sheet and it's quite lightweight. I'm having a tough time finding inexpensive 1/4" plywood in my area.

[48Rob]

Should I be talked out of using 1/4" OSB board? Any good reasons not to use it? It is just so cheap at $9.50 for a 4x8 sheet and it's quite lightweight. I'm having a tough time finding inexpensive 1/4" plywood in my area.

Though some have used OSB, it is a poor choice as it will break down very quickly if moisture finds a way in.
If it will be completely encapsulated, it might hold up, but it is quite a risk to take.

In my opinion, 1/4" OSB is not anywhere near as strong as 1/4" plywood.

Rob

[Irving]

Should I be talked out of using 1/4" OSB board? Any good reasons not to use it? It is just so cheap at $9.50 for a 4x8 sheet and it's quite lightweight. I'm having a tough time finding inexpensive 1/4" plywood in my area.

Though some have used OSB, it is a poor choice as it will break down very quickly if moisture finds a way in.
If it will be completely encapsulated, it might hold up, but it is quite a risk to take.

In my opinion, 1/4" OSB is not anywhere near as strong as 1/4" plywood.

Rob

Not the answer I wanted to hear. haha Yes, it is going to be very encapsulated. The roof, walls and underbody are going to be covered in canvas that is sandwiched between layers of waterproof tightbond 3. Then primer and paint.

[Kody]

My TD will be built using 1/2" ply for the sides, no insulation. The bulkheads will be 1/2" ply, the galley will be 1/2" ply and the ceiling and roof will be 4mm. All glue for woodwork will be Titebond 3.

Kody

[48Rob]

Not the answer I wanted to hear. haha Yes, it is going to be very encapsulated. The roof, walls and underbody are going to be covered in canvas that is sandwiched between layers of waterproof tightbond 3. Then primer and paint.

Hi Irving,

I may be misunderstanding your explanation/plans??

If the glue and canvas will be on both sides of the OSB, and also cover all sides and ends, you might be okay
If the glue and canvas is just on the exterior, the OSB will still absorb moisture.

If you try it, be sure to pay extreme attention to anyplace your complete seal is broken, such as window openings, vents, and especially screws or other fastener penetrations.
I'm a fan of installing fasteners, then removing a few at a time and injecting sealer in the holes before replacing them, to seal both the head and threads of the screw, and the raw material exposed by placing the hole/screw.

Rob

[Irving]

Ended up picking up 5.5mm (7/32") plywood for the exterior.

http://www.homedepot.com/p/5-5-mm-7-32-4-ft-x-8-ft-Underlayment-431178/203183022#.UU9WuDeyItY

It feels quite hard and sturdy for as thin as it is..