Lightweight alternative for plywood?

[CaptD]

I'm framing and insulating my toy hauler now and will soon need to put in some walls. I used coroplast (plastic cardboard) for the ceiling and will use it for the top 24" of wall. I will need something much more durable than coroplast for the remainder of the walls. I will be hauling motorcycles and if one should ever get unsecured I don't want a handlebar going thru/damaging the outer skin. All i've ever seen used for this application is plywood. It is almost the ideal product. I really don't want to be hauling a load of lumber all around the country as I'll need about 13 sheets for all walls. I'll be sleeping in the front section and I'd rather not be breathing in all the off gassing from the formaldehyde in the glues of the plywood. I know about Purebond plywood but its heavy (1/2") and expensive. In this day and age I would think that there would be some kind of lightweight plastic that would be durable enough for me to use while still being lightweight and fairly affordable. If I'm limited to using plywood which kind is the lightest in 1/2" that would still be durable for me to use for impact resistance and that would accept lots of screws and be paintable. Thanks for your response. Darrell

[Rainier70]

The plywood interior is part of the structure. Without it you risk the integrity of your walls. It provides the diagonal bracing that keeps everything working together. Leaving it off or using something like plastic could be a disaster in the making. Your roof could end up south of your floor.

[MtnDon]

Befpre buying our CT everyone I talked to in the CT industry told me the plywood on the interior walls was a structural part, that included a custom builder who has been building since 1982. As Rainer70 stated, the plywood offers the diagonal bracing that gives the walls rigidity. Just like a house uses the exterior sheathing to gain structural rigidity.

[CaptD]

I understand what you guys are saying and that would be true for most cargo trailers. My trailer is a little different than most. Its an all aluminum framed trailer made by a company that makes snowmobile trailers. While most trailers use 1" depth for the ceiling ribs mine has ribs that are 2" deep. It is designed for snow load weights. I further made it stronger by adding 3 rows of 1x4's run lengthwise. I used 3 3/4" of foam insulation plus the coroplast for the ceiling. Really lightweight materials up there. The trailer came (new from the factory) with no wood anywhere - no type of walls - as its not needed with 16" on center aluminum ribs. I questioned why no wood walls and the builder said its not needed to support the walls. I had the factory add bracing - aluminum supports welded in - run the full length on both sides about 36" high as I plan to add E-track for tie down purposes. I have also run 2 lengths of 1x4's and 1 length of 1x8 along the walls for screwing the outer walls in place and attaching various items. Structurally it is designed pretty strong. I am just looking for a lighter weight substitute for the heavier plywood. Thank you for your input. Darrell

[Padilen]

I looked at many trailers without plywood and I lived in a house without plywood. It was a mobile home with 2x6 struts (batt insulated), 1/2 inch ridged foam under vinyl siding. It towed just fine. Code for stick builds for awhile you could build like my mobile was but plywood at corners- and min of 1 inch ridged. Unsure of codes now because I'm no longer looking, had my home built in2001-with plywood but no ridged foam- nu-wool insulation.
My aluminum trailer has "white board" paneling, not plywood, not for structural strength. Many different types of CT construction from economy to premium. From T like steel "struts" to rectangular tube, some may need plywood for strength others may not.

[Greg M]

There's a plastic used for lining horse stalls and such that some folks looked at as a skin a few years ago. I think it was called polywall or something similar. It expanded too much to be used out in the sun, but it might just do the trick inside. If it's tough enough for horses it's probably tough enough for toys.

[Kaz]

Dibond is an interesting substrate has been on my radar, worth looking at. Just my 2cents.

hartsupply.com

[aggie79]

Dibond is an interesting substrate has been on my radar, worth looking at. Just my 2cents.

hartsupply.com

Among hundreds of other ideas I've been kicking around, I thought about building a cargo trailer with square aluminum tube framing and Dibond or other aluminum composite material (ACM) on both sides of the framing. The ACM would be held to the framing by a combination of VHB tape at all framing members and riveted at the top and bottom (and perhaps at the sides of the sheets.)

This would make a very strong and lightweight panel although it wouldn't provide much of a thermal barrier.

[Mike S]

There's an engineered material called Azdel that's being used for walls and cabinets in higher end truck campers and travel trailers. It's touted as being light, strong, and attractive. I've tried to find it for my build but it looks like it's only available to manufactures in large quantities. See if you have any better luck sourcing it.

[Tom Kurth]

How about insulating the sidewalls with rigid foam thoroughly glued to your aluminum siding, then glue 1/4" ply or waferboard over that? The combination would make a monocoque structure similar to strip-built canoes.

Best,
Tom

[CaptD]

Thanks for the reply guys. The Polywall expands to much to be used. The Dibond is to expensive. Azdel looks like the best to use for the walls and its already being used in the rv industry but the only source for purchase that I could find sells it @ 250 sheets at a time. Like I said in my original post I would think that in this day and age we could buy some type of composite panel that could replace plywood. I'm still undecided. Maybe use 1/4" plywood and then coroplast panels over that. No priming and painting needed and then the walls would match the ceiling which is finished with coroplast.

[MtnDon]

Like I said in my original post I would think that in this day and age we could buy some type of composite panel that could replace plywood.

Except for specialty markets like RV's, aircraft and the like, there is likely no market for a lightweight and more expensive product. That's my guess as in home building price is a driving factor and nobody cares what it weighs, unless you are the guy carrying it in.

[Rainier70]

It would be a little thicker, but how about bonding a nice 1/8 inch finish ply like birch etc to 1/2 or 3/4 inch blue or pink foam board?

[lrrowe]

It would be a little thicker, but how about bonding a nice 1/8 inch finish ply like birch etc to 1/2 or 3/4 inch blue or pink foam board?

Which is exactly what I am going to do for the interior walls around my shower unit and to separate the "living" area from the "galley" section in the rear.