Modern building materials in vintage restorations

[bredlo]

This may have been covered, I didn't to a thorough search.

As I'm looking down the barrel of a full frame-off restoration of a '63 Globe Trotter, I'm wondering about floor materials, insulation, etc.

The first thing that everyone says when you're considering an older model is to check the floor for rot. Another big problem is the insulation, especially in the belly pan where I hear it crumbles and compresses after decades of service.

It makes me wonder if there are modern alternatives to consider when replacing my floor and all insulation in the walls, etc.

First: Sub-flooring materials Aren't there formed, recycled plastic alternatives to 5/8" plywood by now? I'm aware of backyard decks which use 2x4's of recycled milk jugs rather than lumber. They look like wood, drill like wood, and never rot! Wouldn't this be a great alternative to plywood flooring, if weight was comparable? Even lightweight MDF which doesn't expand/contract in weather and is naturally more unlikely to rot would be better, no?

Second: Insulation I've seen half a dozen episodes of This Old House which uses a new kind of spray on foam insulation rather than the old "Pink Panther" Corning stuff. If one's inside skin were already off, wouldn't it make sense to spray on this stuff, which is superior to the old insulation in it's:
• heat retention
• flexability to move with the structure
• ability to seal out air leakage better than others
• completely non-toxic to the environment
• I imagine it wouldn't be prone to mold sitting in the belly pan like paper-backed fiberglass probably does.

There used to be a problem where this stuff would burst out of walls, etc. But newer kinds are slower to activate and don't create as much pressure on the walls, so one wouldn't need to have nightmares of rivets popping off and aluminum sheets flying across their backyard.

Just some ideas I'd like to bounce off everyone before beginning restoration. Lightweight, rot-proof alternatives to the stuff available in 1963 makes good sense to me, and would be appreciated by someone who didn't have to do it over again in another 40 years!

Brad

[Silvertwinkie]

I'm not really a vintage guy, but I think I can say this fairly safely.

From what I've seen, Airstream uses a bunch of standard parts that can be purchased at any Home Depot, etc.

I would assume that if you do a body off frame rebuild, that you should be able to use almost anything you desire that is within reason. I like pressure treated lumber (or in this case plywood). The coach has been designed for that weight. The other thing to consider IMHO is the fact that some of the materials you mention I do not think have been tested enough in the harsher moving application of a trailer. Most of those materials are stationary. I can say first hand in the '03 Bambi, that some of the engineered wood cabinets, etc tend to be less able to hold screws. I have had a few pop on me whereas I think real wood installed correctly would have held it better. I am sure the same holds true for some (not all) other engineered products.

One thing to consider when talking about insulation is the "R" value. There are several options out there, but as far as I've been able to see, fiberglass batts get better "R" value than most around. You can get it enclosed in plastic, faced, unfaced, etc. Whichever way you go, make sure to wear protection when dealing with the stuff.

Eric

[wahoonc]

I don't see a problem using modern material in restoring a vintage unit, but make sure the "newer" material has the same structural ability as the older one. As far as the insulation is concerned you will be hard pressed to find something as versatile as the new generation fiberglass to give you the R-value per inch, flexible installation...it won't fracture or crack when flexed, as well as ease of installation. Another factor to consider is that a lot of the foam insulations lose R-value as they age, as well as the chemical off gassing. As far as the floors are concerned I don't know of anything that would work better than plywood, unless you wanted to use an aluminum planking. Most of the wood composite boards on the market are not as structurally stable as a good grade of plywood, same goes for the plastic resin composites. Ever seen on of those after it has been laying in the sun unsupported? Just a few thoughts....

Aaron

[j54mark]

I would be very hesitant to use foam of any kind in the walls. The walls, in fact the entire coach, "work" a tiny bit as it travels, or just from heating up and cooling off everyday. This slight movement is likely to cause foam to crumble and self-destruct. Fiberglass R-value can be increased slightly - slightly now - by stuffing in oversized batts. That is to say, a standard 3 1/2" batt made for stud walls can be stuffed into the 2" space available. You will not get R-11 out of it, but it will be better than R-6.

There is a problem with fiberglass in the belly areas as it gets wet, stays wet, and loses insulation value. I would think that here the closed-cell foams might be just the thing. If not, I'd be interested to hear why not.

The floor in an integral part of the structure. It is not just something to stand upon. Airstreams are unique as being a monocoque structure, and the floor is the element that ties it together. My point being that you need to use as large of panels as you can to minimize breaks in the continuity. Also, there are panels that are not particularly subject to rot, but tend to come apart if wet for long periods. I'm thinking that MDF is one of those?

Mark

[fundave]

These are the questions I've been pondering. Especially the insulation. I've been considering the foam type, I read somewheres that the Argosy uses that type.? I'm not ready to insulate right now, but, at the moment I still think that the foam is the way togo/./ but hey Im a rookie.
Flooring materials...pressure treated seems the waytogo...yet Ive heard that there are some composite boards that are stronger and less prone to rot. Again the jury is out on this too, right now I'm leaning towards the marine grade plywood. I would like to reduce the weight of my finished ttralier so I've been a looking at the issue(s).

[bredlo]

All great points! I'll keep these things in mind as it gets closer. That closed-cell foam I'd forgotten reading about, but it seems like a cool alternative to regular fiberglass insul. for the belly. That's an area that seems famous for getting wet, improperly draining, developing holes from little rocking kicked up on the road, etc. As I progress with resto, I want to make sure my belly pan, rust protection on the frame, and flooring are done with the best materials available. Weight, initial cost and performance over a long period of time seems to be the 3 variables with anything in the trailer construction arena.

Surely a visit to an RV show to talk with the salespeople - or even better - a tour of the Jackson Center plant before I begin will be illuminating as well.
Brad

[Silvertwinkie]

When I go to Jackson Center, I'll take some photos of the flooring if I can and some of the materials. I should be out that way in a few weeks.

Eric

[bredlo]

Eric, that'd be great fun for us all to look at, thanks! I'll be curious if they even let you take pictures. The fact that their site is the only place I've seen photos of the plant makes me think perhaps not, otherwise I'd shoot a little video myself!

Alright, it's back to the weather channel for me. Looks like I'll have snow Wednesday for my trip back east from Seattle. At least I'll get most of my scary towing experiences out of the way on the first try, right?

[74Argosy24MH]

I wouldn't use pressure treated plywood because of the chemicals used and out gassing in an enclosed area. Unless you can get an engineer to confirm that the plastic decking would withstand the stress I would avoid it. Floor changes are a lot of work and I wouldn't want to have to do it twice.

I used spray foam in my walls. The point about flex is valid, but fiberglass is also going to break up and settle. It will also hold water like a sponge, something the spray foam won't do. The difference between the foam and fiberglass is definitely noticeable (although whoever did the fiberglass left a lot to be desired). It does and doesn't stick to the aluminum. I can cut a square in it and pop the piece out. So it does not adhere to aluminum the same way as wood with a rougher surface. FWIW one of the foam manufacturers gave me a contact to speak with in Indiana who supplied the rv industry, apparently it is a fairly common use.

Another thing I did is to use foam tape on the ribs before reinstalling the interior. Anything for a thermal break with all the aluminum skins and ribs.

I used foam board under the floor, no water absorption and hopefully it will last longer than fiberglass.

John

[Silvertwinkie]

From what I've read, they do let you climb into one on the line...and I've heard that they do let you take pictures of the bare interiors, so whatever is availibe, I'll be sure to take as many digital pics and post them.

I thought the newer pressure treated woods were a bit more safe than the old type.

Eric

[Moonshot]

Are you talking about the compressed foam that you get in a spray can? This stuff can harden like a rock if sprayed on thickly. If you needed to tighten a drain fitting or isolate a leak you might spend hours tearing that stuff out. Maybe if you spray it on lightly it wouldn't be quite so bad, but then wouldn't your R value be adversely affected?

And isn't treated plywood substantially heavier than nontreated plywood?

Just some thoughts.

Scott

[Silvertwinkie]

I don't think that it is. If it is, I can't see it being substantially heavier than conventional plywood. Of course I cannot say for a fact.

[bredlo]

Originally posted by 63wind
Are you talking about the compressed foam that you get in a spray can? This stuff can harden like a rock if sprayed on thickly. If you needed to tighten a drain fitting or isolate a leak you might spend hours tearing that stuff out. Maybe if you spray it on lightly it wouldn't be quite so bad, but then wouldn't your R value be adversely affected?

And isn't treated plywood substantially heavier than nontreated plywood?

Just some thoughts.

Scott

I don't imagine the foam 74Argosy was referring to came from a can. The stuff I was referring to, anyhow, is professionally sprayed on by a guy in a white jumpsuit. It reportedly stays flexible, and has higher R value than fiberglass. (Because it gets into the nooks and crannies?) The fact it doesn't stick to the aluminum wouldn't bother me... it would essentially be a block of foam in the exact shape of the cavity - a cool (er, warm!) concept.

Anyhow, I'd definitely pass if it would make repairs down the line impossible. A valid concern, 63Wind. 74Argosy, I'll look into the chem outgassing issue before proceeding - I wouldn't want that, but it seems many people use it so it may be a negligible amount.

[diesel]

On bus conversions, many folks use these products. I will probably use the ceramic-based Thermal-Coat on the roof of my Airstream for more insulation. The white paint up there is getting thin and easily scratches off the rivits. The Prevost Conversion we are working on now has a rivited aluminum roof. The remaining body is stainless steel.

Once the outer shell is exposed, floor sheeting removed, and utility openings made, the Thermal-Coat is applied to the walls, roof, and floor including the framing. Next the utilities are installed. Then the polyurethane insulation is applied and smoothed. Then the "The Insulator" is installed. Once that is done the interior skin is applied. Spend some time at the following link and see how it is done.

http://users.cwnet.com/thall/thermalcoat.htm

There are other methods out there. Just make sure that what you do will last as long as the Airstream.

[87MH]

Treated wood is normally purchased saturated with water (and the arsenic compound) therefore it weighs more "out the door" than non-treated kiln dried wood.

Once it is dry, the weight is practicaly identical to non-treated wood of the same density.

As far as outgassing, unless you use it for toothpicks or eating utinsels, the danger by exposure to the arsenic compound (once it is dry) is minimal, especially when covered by flooring.

When you consider the minimal amount of time people spend in the trailer, the high number of times the air is changed, and the hidden nature of the floor, the exposure is not even comparable to the dosage received when handling new, wet (saturated) wood, or the amount of exposure when cutting or working (sawdust and moisture contact)with treated wood products.

[74Argosy24MH]

The insulation is a 2 part, but I used the spray can also. When I did it I covered the water fill, electrical openings, furnace, etc. with masking tape and sprayed everything. Then cut the openings from the outside and filled any gaps with a spray can.

You will end up with some wires buried but if you do it right the wire itself usually isn't a problem. Run spares and take pictures. Repair is easy because you can cut it out and fill back with the spray cans.

Diesel the Thermalcoat is interesting. I used a latex based ceramic insulation on the top of the inner panel above the driver and passenger. It made a lot of difference. The price was about twice Thermalcoat. That price should make it affordable enough to do the whole interior.

John

[WayWard Wind]

Eric---A/S does let you take pics inside the plant, at least they did this Fall when we were there. took all the pics I wanted, even let me inside some units in the building progress. If I knew how to post pics I would have some put on the forum. Alas I'm not computer smart. I think who ever has the opportunity to visit the plant should go, as it's really an experiance to see how it all goes together. Probably makes more sense if you're restoring a unit, as one can visualize all sorts of "possible upgrades"
Best,

[Davydd]

The good news is that plywood sold after March should not contain arsenic. That's when the law goes into effect.

There all kinds of spray foams. The polyurea or polyurethane types are the ones you will want to use. They have that beer color look. The R value is nearly twice fiberglass. Polyurethanes are used in stress skin panels. I would think between two layers of aluminum it would add to the structural integrity.

There are other types that are sold for filling concrete block cores that are essentially useless. If it sprays white don't use it. Test a sample of the foam to see if it will absorb water and reject it if it does.

[markdoane]

Brad,
Good luck on your restoration. I'm doing the same and have considered many of the same questions.
Regarding flooring, I looked at some plastic panels (Codemco, for example). Weights were slightly to a lot more than plywood, depending on material and amount of air incorporation. The lightest was a foam polyethylene, but mechanical properties (Elastic Modulus, etc) were not as good as plywood. I think the best alternative might be end-grain balsa with epoxy resin. There are vendors who will custom make these panels for you if cost is no object. I'm going to stick with high quality plywood with epoxy edge sealant.
For insulation, there are lots of applicators who can spray a closed cell foam. This is a very attractive option. I understand that the quality (waterproofness) of the foam depends a lot on the skill and training of the operator.
I plan to install closed cell foam sheets, where the sheets were made in a controlled factory environment. I think the integrity of the closed cells is probably a lot better. These are polyethylene or polyprop or urethane. I would stay away from the common foam building products that will probably disintegrate with the amount of shaking that a trailer gets.
Here's a site that has info on closed cell foams Polyolefin foams