plywood thickness on the roof

[oklahomajewel]

Rubber roofing? you mean that roll on stuff called elastomeric or something? Can that be applied to primed wood or bare wood?
I wondered about that.

Julie

[IraRat]

All you need is 1/4, nothing thicker and certainly not more than one layer.

You also have to remember that depending on the ply that you use at 1/4, it's not going to easily bend to match the curve there. There's a semi-difficult process to moisten/heat the ply to make it bend (Madjack, help?), but I wanted to avoid this, so I ordered specialty "bendy" birch ply that I had shipped all the way from Massachusetts down here to Florida.

Since you're covering with rubber, there are probably a bunch of different materials you can use that are available in your area. It's a different story when you're concerned how it's going to hold up totally exposed to the elements, how it's going to hold stain, varnish, etc.

But 1/4 thick is all you need. Once it's attached to correctly placed spars, it'll be rock solid.

I don't know what you mean by hardwood, though. Masonite? The masonite debate has continued to rage on, but the majority consensus here is to use ply, albeit whatever type, and not masonite. In ply, there's real glue there in real wood layers, which is a good thing. Masonite is kind of like sawdust semi-held together by semi-glue.

It's just not the same thing.

[Roly Nelson]

Powderburn, I used 2 layers of 1/8 inch lauan plywood on my roof, glued together with liquid nails/panel adhesive, which comes in a tube and fits in a caulking gun. 1/8 inch is much easier to bend, and 2 layers is stronger than one layer of 1/4". The best place I have found to get this cheap lauan plywood is Lowes or Home Depot. Good luck.

Roly ~~

[asianflava]

I too am using 2 layers of 1/8in luan. I had to go to a lumber store to find it though. Lowes and Depot in my area didn't have it. I glued the layers with the polyurethane caulk. I still haven't decided if I will leave the hatch and rear roll pan with 1 layer of ply.

[randy chesnutt]

i went to lowes an got 1/4" exterior grade plywood, it bent real easy side to side. end to end was much harder. i run my plywood side to side. started in front to rear and the second layer,rear to front. i wanted a strong roof. thas a major part of the trailer. i took my plywood drops and used for cabinet.

[IraRat]

Powder, your simplest solution is the 2 sheets of 1/8 luan, glued together, as described above. It'll bend real easy for you. The interior roof/ceiling is a much tougher bend, but that same material will work fine. (I think one layer is all you need for this.) You have to be real careful with it though--it can break if you're not careful.

Be aware of two things though:

The luan might not be labeled 1/8. At my Lowes, this thin luan is labeled in millimeters. (Don't remember how many millimeters because I didn't use it.) Also, although you're going to cover it with rubber, you may still want to seal it first--although this may interfere with your adhesive properties.

Unless you're very familiar with this rubber you want to put on there, I would be extremely careful and do a lot of research on that material. Holding up to UV is the big thing--faded black is pretty ugly. And also, you are now choosing your roof skin based on this covering, you're going to be adhering it rock solid, and after you do that...there's no turning back.

It's not like in a year, you can remove that rubber and stain/varnish the wood. You would have to skin it with yet another layer of something.

[IraRat]

Is luan made with exterior glues?

That's the thing:

From what I understand, Luan is not a good exterior wood. It works for a TD when it's covered with aluminum or some other substantial skin--but not as the sole material you would want to stain and/or varnish for exterior use.

Again, I said from what I understand and what I've learned here.

Am I right on this guys?

[len19070]

I used 1 layer of 1/8" laun...But! My Aluminum Skin is 80 ga. I had to get the Aluminum that thick to get it in the pre-finished color I wanted. (still cheaper than painting it) On other trailers that I have used a 32 ga. aluminum skin on I have used 2 layers of 1/8" laun laminated together.

http://pg.photos.yahoo.com/ph/len19070/ ... /my_photos

Happy Trails

Len

[Roly Nelson]

IraRat, I used that cheap "not-for-exterior-use" lauan on both the top and sides. Coats of varathane seem to keep it in pretty good shape after 2 1/2 years of use. However, if I were to do it again, I would spring for a better looking plywood, since the lauan has faults that are hard to hide during the building process...............Roly ~~

PS, just check out Doug Hodders build and you will see what I mean :-)

[doug hodder]

Thanks for the compliment Roly....I used 4x8 sheets of Okume mohogany for the sides ...it's marine grade, no voids in the layers and the top veneer is finish ready. no plugged voids, or filler...marine grade also uses a different glue. I used 6mm approx. 1/4 inch....any lighter and I would have had to have it shipped in...Substrate under aluminum on the roof is 1/4" luan....Doug

[purplepickup]

I used 4x8 sheets of Okume mohogany for the sides I used 6mm approx. 1/4 inch....any lighter and I would have had to have it shipped in.
Doug

Doug, I have a couple of questions. There's a specialty plywood shop an hour away and according to their website they have Okoume plywood in 4mm for $37 and 6mm for $53 for a 4x8 sheet, graded A-A. Do those prices sound about right? Is all Okoume made from mahogany? And, do you think 4mm is too thin for the outer sidewall skin? I'm planning to use 3/4" framing and insulation glued to both the outer skin and the 1/8" interior wall to make a solid sandwich wall. I'll also be glassing the exterior.

[doug hodder]

Pricing is correct...yes Okume is mohogany....if it were me, I'd do the 6mil on the exterior and save the money on the cloth and just epoxy it...Glass cloth ain't cheap and if you haven't wetted out large sheets of it, can be a learning experience....just my thoughts....Doug