exterior glue on 3/4inch cabinate grade ply?

[Southern Oregon Bob]

I started my frame today and went ot buy my 3/4 inch 4x10 ply for the sides. I was planning on getting ACX for 55$ when I found out they had gotten some 3/4 4x10 in rustic alder for 65$. From past experienses I've found the cabinate grade plywood to be of better quality and tends to stay flatter, but the salesman recomended I not use it because it would'nt have ext. glue. I read somewhere that most all ply these days use ext. glue. Is that true. If not do I need ext. glue. I'll have alluminum on the outside and 3/4 inches of foam and then 1/8 on the inside. I was mostly worried about condensation in the wall. Any thoughts to help me make the right choice? Thanks for any and all knowledge Bob

[Guest]

Bob,
Although 3/4" plywood on the exterior side of your insulation may sound a bit heavy to some, you should seal it regardless of what type of glue was used to make it. When you cover that plywood with your metal skin, you are going to get condensation between the metal skin and the plywood, so have a good sealer on it.
I'd say the two most common sealers are varnish and epoxy.

[Southern Oregon Bob]

Would I be better off using the 3/4 on the inside and the 1/8 or1/4 on the outside. I like the look of the rustic alder but I was only planing on using the double wall and insulation on the cabin portion, but if that would work I could add some 1/2" and no insulation to the 1/4inch side in the galley, and that would allow me to use some cheaper ply on the outside. The only other 4x10 I can find in my area is 1/2" cdx and it seems to start warping before you even take it off the pile. Open to suggestions Bob

[Guest]

Bob,
I'd stick with the thicker plywood on the outside of the wall.
I understand your feelings about not wanting to go with warped plywood.
If that 3/4" cabinet grade plywood is the only flat stuff you have to choose from in your locale, I'd say go for it.
Also, if that 1/8" plywood is the only nice stuff you can find for the interior, I'd recommend doubling up on that to get a 1/4" on the interior.
On another note, if you're considering eliminating the insulation in the side walls, just go with the 3/4" ply by itself, with the metal exterior skin.
BTW- I've been known to overbuild things just a bit.

[mikeschn]

Would I be better off using the 3/4 on the inside and the 1/8 or1/4 on the outside. I like the look of the rustic alder but I was only planing on using the double wall and insulation on the cabin portion, but if that would work I could add some 1/2" and no insulation to the 1/4inch side in the galley, and that would allow me to use some cheaper ply on the outside. The only other 4x10 I can find in my area is 1/2" cdx and it seems to start warping before you even take it off the pile. Open to suggestions Bob

You're adding a lot of weight using 3/4" plywood. If you are building up a wall with sticks, then use thin plywood on both sides. The sticks will straighten out the plywood for you!

Mike...

[Southern Oregon Bob]

My side is 4'6"x10'. If I step down to 1/4" on the outside I would have to use three pieces. Is there a good way to splice 1/4" ply. I can get 1/2" cdx in 4x10 would that still be over kill and too heavy with insulation and 1/4 on the inside? I've made my pattern and I'm ready to roll I just need to make some decisions and the more I read the harder it is to do that. Bob

[mikeschn]

Steve built up my Lil Diner out of 3 pieces of 1/4" luan. Apparently, the trick is to strengthen it with fiberglass... Check the Lil Diner thread, or Steve Fredricks webpage...

Mike...