Questions about repairing / replacing foam wall panels

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HotTommy

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Mar 8, 2014
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I recently purchased a 2000 Georgie Boy Pursuit motorhome.  I subsequently discovered water damage in the walls and floor below three windows in the living area.  I've removed the damaged OSB flooring (wall to wall) and replaced it with plywood.  I removed all the cabinets and one of the windows today to get a better look at the interior construction of the wall.  The wall appears to have been a multilayered structure consisting of (from the outside to the inside): a fiberglass shell adhered to 1/8" luan plywood, adhered to 1-1/2" styrofoam insulation, adhered to another 1/8" luan plywood, covered with a vinyl wallpaper.  In the areas damaged by water the luan turned to mush except the the thin layer still adhered to the inside to the fiberglass.

As I removed some of the damaged luan and foam, I was surprised to discover there were no studs or supports for the window of any kind except the foam board itself.  I subsequently read elsewhere that the factory likely vacuum sealed the exterior fiberglass shell and foam wall board together as a unit before attaching the completed wall assembly to the chassis.  Apparently that technique provided enough strength and rigidity to reduce or eliminate the need for studs.  (Remind me to not be in a motorhome that flies off a cliff and lands upside down.)

I've read a lot about how to glue plywood/foam to the inside of the fiberglass to minimize delamination bubbles, but I'm not comfortable about installing a foam board patch in a wall that was intended to be a single structural unit.  I'm thinking that instead I might establish the outer limits of the patched area with vertical studs from floor to ceiling, and augment those with a framework of studs around each window.  My question for those of you who have taken on this or a similar job is this.  Does my understanding of how this RV was constructed sound correct, and does my approach sound good, bad, insufficient or overkill?
 
I believe you have analyzed the situation correctly. Your approach to a solution is right on. The vacubond system is good and strong to a point. When compromised with water, is just have you found out. Good luck with your repairs. Post some photos.
 
Kevin Means said:
Hey Tommy... just a reminder... you don't want to be in a motorhome that flys off a cliff and lands upside down.

Kev  ;)

Thanks. I'm going to print this out and tape it to the dash by the sign that says, "Don't drive under anything lower than you are."
 
I think the studs are a necessity.  Does the roof have wood beams to attach the wall beam to?  What is going to attach the new wall to the existing wall?  If there's different flex at the seam it could split.  Could you extend the plywood a couple of feet past the seam for support? Good luck. 
 
Good questions, and much the same as ones I had.  ... Plainly, I need to replace the portion of the foam board that has delaminated from the fiberglass.  But it would be counterproductive to remove the foam board that is still firmly attached.  The question is how to attach the new material to the old foam board.  Even if the new material and adhesive are plenty strong, I can't imagine the raw foam it contacts will stand much pull or stress.  So my plan (for now) is to adhere the new studs to the fiberglass very close to the old foam board.  When all is secure, I'll squirt expanding foam insulation into the crack between the stud and the old foam board to fill whatever gap remains.  It won't be as strong as the original structure in some directions, but it should be plenty strong for supporting the ceiling and roof. ... As before, I welcome comments and constructive suggestions.
 
At one time I worked in the Travel-Mate plant, that is how we made the walls and roof. The foam was laid out in a jig, sprayed with a contact cement (horrible to work with on a hot day, we would all get high from the fumes) then the laminate was laid on. Flipped it over and did the same with the aluminum skin. The only wood used was for attachment points. Very strong and light stood on edge, the roof needed the cabinets for support. One customer picked up his new TC on Thursday, back Monday. He had driven under an arch that was a tad lower than his camper. Insurance wrote it off. We probably could have repaired a conventional stick frame.
Your approach is the only way I can think of short of replacing the wall. The most difficult part will be removing the remaining adhesive without damaging the shell.
 
So I'm rethinking my approach to this problem.  I've removed all the damaged wall near one window.  The portion I removed is about three feet high and about seven feet wide.  The portion that had been wet and delaminated from the the exterior wall was relatively easy to remove.  I removed a little extra wall both to make sure I had revealed all the wet area and to square off the edges for the patch to come.  That was when i learned how difficult it is to remove the wall board from the undamaged portion of the exterior wall.  That made me reconsider my plan for a floor-to-ceiling stud and I've come up with a different approach.

The idea came to me when I was considering how to make the foam sandwich patch I will need to install.  The total thickness is 1-3/4" and I know I will use 1/4" thick water resistant plywood on the front and back.  If I use the standard 1" thick rigid foam board in the center, I'll still be about 1/4" shy of the thickness I need.  That's when it occurred to me that I could make the sandwich with three sheets of 1/4" plywood and two sheets of 1/2" rigid foam board glued together in alternating layers.  I can glue them up like one big 4' x 8' sheet on the floor of my garage and press them together with some heavy weights.  It will be a poor man's version of the way the wall was constructed at the factory. ... After the new sandwich is cured, I'll trim the whole thing to fit in the waiting hole.  My patch should be stronger than the original foam board.

The final task will be adhering the patch to the fiberglass skin.  For that I plan to apply a very thin coat of polyurethane glue to the fiberglass, and water to activate it to the plywood on the patch.  I have an idea for a clamp system that will allow me to press a sizeable portion of the skin firmly against the patch.  A roller should allow me to force all of the skin to contact the patch at least some.  The polyurethane should expand some while curing to fill most of any voids that occur.  I'll just have to be careful to not use so much glue the expansion causes problems.

In the end I expect the patched area to be at least as strong as was the original.  However the seam where the old and new meet will remain a weak area.  To help address this concern and give the inside of the motorhome a more uniform and finished look, I will cover both the old and new walls with 1/8" thick fiberglass reinforced wall panels.  These waterproof panels should add some strength and rigidity to the walls.  Given that the entire upper structure of the beast is made up mostly of styrofoam glued to plastic, I think this will be good enough for me.  As always, your comments are welcome.
 
Progress has been slow as I've been working on several other projects simultaneously.  But here's where I'm at and some of what I've learned.

The three known areas where water caused the factory wall structure to delaminate from the exterior fiberglass were all near windows.  All of the damaged wall has been removed.  A new wall panel for the largest damaged area was built and installed as described above.  The window above it was removed and resealed.  Several strong rain storms have not revealed any new leaks.  ... Panels for the two remaining areas are nearly finished.  One damaged area was by the front passenger seat and included the place where the heavy rear view mirror mounts.  A solid wood 2x6 cut to length will just fit and provide the heft and strength needed to support the mirror.  The third damaged area was near the dinette.  The damaged wall portion that was removed included several sheets of strategically placed thin steel that allowed the dinette furniture to be securely fastened to and supported by the wall.  I will have to be sure the new wall can adequately support the new dinette I will build.

One lesson I'll share for anyone else who tries this job regards the fabrication of the replacement wall panels.  As I described above, they were made with alternating sheets of 1/4" plywood and 1/2" foam insulation board.  The plywood is actually called underlayment and is made with a glue that, unlike conventional plywood, is water resistant.  The glue that secures the foam to the plywood must be specially intended for use with foam insulation.  Otherwise, it may eat through it rather than stick to it.  ... My first gluing job failed because none of the product instructions mentioned, and I didn't notice the very thin sheets of clear plastic that cover both sides of each foam board.  The glue stuck to the plastic, but the plastic peeled away from the foam board as soon as pressure was applied.  After I removed the plastic sheets and reglued everything, it stuck together well.

I've been taking pictures along the way so I'll have some to post soon.  I'm looking forward to moving from the deconstruction phase to the reassembly phase.
 
If you can, park it near a large wall, then you can place a sheet of plywood on the outside and brace it with 2x4's against the wall to give you some flat pressure. then after placing the patch brace it tight on the inside.
 
captsteve said:
If you can, park it near a large wall, then you can place a sheet of plywood on the outside and brace it with 2x4's against the wall to give you some flat pressure. then after placing the patch brace it tight on the inside.

Cool idea.  I parked my old pickup truck next to mine and used it to help secure the outside bracing.
 
Time for some photos, but I can't figure out how to insert them.  These links show them.

Here is a picture of the largest damaged area with the old wall removed.  The blue in the window opening is a tarp to keep weather out.  You can also see that some of the floor has been replaced.
https://lh6.googleusercontent.com/-dlXUKbqFFYU/U0_dfssEizI/AAAAAAAAA4c/RVbrqPpakvw/s640/Damage%2520removed.jpg

This is an edge view of the repair panel made of alternating layers of plywood and foam board.
https://lh4.googleusercontent.com/-5HwlfyYfAQg/U0_dk8eVH5I/AAAAAAAAA4s/RafCoJK0BYs/s640/Wall%2520panel.jpg

This shows the large patch panel clamped in place while the glue dries.  The two vertical pieces of lumber are part of the clamp system.  The second photo shows the clamp from the outside.
https://lh3.googleusercontent.com/-BMWv-1znmcA/U0_dfvIlioI/AAAAAAAAA4Y/F9NlhT6LAhs/s640/Patch%25201.jpg

https://lh3.googleusercontent.com/-a8PV0Q93TQU/U0_dgKGTnaI/AAAAAAAAA4k/A7kx4c5Jo10/s512/Patch%2520clamp.jpg

This shows one of the smaller patches being test fitted by the passenger side window. You can also see the vertical 2x6 toward the front that is needed to support the outside mirror.
https://lh5.googleusercontent.com/-3cHrkaG7PP4/U0_dfhl3tTI/AAAAAAAAA4U/oejW_iDrZmM/s512/Patch%25202.jpg
 
[quote author=HotTommy]Time for some photos, but I can't figure out how to insert them.[/quote]

Photos are attached to posts, not inserted. Here's how. Posting links like you did is also a good way to display your photos.
 
Man was this helpful...This is my first RV and purchased a 2005 Georgie Boy Pursuit so scouring the web for information. Like yours, it appears that a few of the windows also leaked causing damage to the walls and floors.  Driver's side looks identical to yours.  I have opted not to totally replace the floors except where the damage occurred but will have to replace all of the flooring on the slide outs.  Trying to come up with ways to attach the bottom portion of the plywood/insulation sandwich on the push outs without actually removing the push outs like I have seen on You Tube.  Thinking of using some of that 4x8 ABS sheeting for wet locations sold at Home Depot and others instead of wood with the aluminum covering which was worthless. Attaching with adhesive and screws to the underside of the 5/8" flooring above and using some sheets of plywood and floor jacks to raise and hold in-place while the glue is dying.  I have done a lot of remodeling in homes, but this seems like it is a lot more labor intensive.

By the way.  I have one of those Fein Multimaster saws.  It has been great in removing delicate areas.  Used the knife blade without teeth to remove the Styrofoam without damaging the fiberglass outer sheeting at all.

Thanks for documenting and thus shortening my learning curve. 
 
Has anyone had any experience using these instead of Luaun plywood for the backing for the fiberglass?

http://www.uline.ca/BL_1854/Plastic-Corrugated-Pads

- Rich.
 
No direct experience with the product.  I believe the lauan is there to add some rigidity to the side walls similar to using plywood on the outside walls of homes when they are being built.  How would this compare? It is amazing how flimsy the skeleton framing is on these things are until you glue, screw, and staple the pieces parts together.  It would certainly be great to come up with something that would not deteriorate if it got a little wet and minimize the delamination associated with it.  $35 per sheet is a lot more costly than lauan too so maybe the reason the factory does not use it.  Their focus is on cost and weight.   
 
I'm also repairing some damaged walls on my Fleetwood bounder. My question is, what kind of glue did you use to adhere the styrofoam to the plywood?
 
Some people use foam construction adhesive that can be purchased at any hardware store.  I personally use West System Epoxy with the appropriate filler and hardener.  There are contact adhesives that can be used, check to make sure they are compatible with the foam insulation, but what I liked about the West System Epoxy is that it gave you the wide uniform coverage plus time to move the luan or plywood around for proper alignment.  When using contact cement, once the two surfaces touched that is pretty well it.

Not sure what type of hardener or filler to use? Call West System technical support.  They are very knowledgeable about RV applications for their product.  I used their 403 filler when addressing some delamination and the 406 when using it as an adhesive to thicken it up.  http://www.westsystem.com/ss/406-colloidal-silica/. 
 
This thread is great and just what I need. I just bought an 04 Jayco Granite Ridge 3100ss. I knew it had a little de lamination on the drivers side by the cabover bunk. Upon further inspection it is worse than I thought.
I have torn out the whole wall in the bunk including the styrofoam. With it came SOME of the wood that was glued to the outside wall (fiberglass). When I say some, I mean a layer of it came out. There is still a layer glued to the fiberglass. How do I get the rest of the wood off the inside of the exterior wall?  I really don't want to open the exterior wall since I just caulked and Eternabonded the whole front of the RV. I believe the leak is repaired.
I'd like to just repair the wall from the inside.  Pics are attached.
 

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