Flooring Plywood Delaminated

[jolandua]

We are new to your community - just bought a 1994 Winnebego Warrior with 44k miles. I'm looking for advice on repairing de-laminated floor plywood sections. We will certainly find and correct any water leaks first - really looking for materials and process to correct the delaminations. Could I maybe replace the plywood with a dense polystyrene (etc.) extrusion? Anyone with experience along these lines?

John O.

[zero]

We are new to your community - just bought a 1994 Winnebego Warrior with 44k miles. I'm looking for advice on repairing de-laminated floor plywood sections. We will certainly find and correct any water leaks first - really looking for materials and process to correct the delaminations. Could I maybe replace the plywood with a dense polystyrene (etc.) extrusion? Anyone with experience along these lines?

John O.

I've got experience with plywood in campers. Not specifically with a Winnebago Warrior. RVs tend to use a better grade plywood then you're going to find in a local lumber yard or Home Depot/Lowes. I'd never use any of the low-ply pine plywood they usually sell. If you want to keep weight down with thin plywood that has strength - get some marine-grade fir plywood. The overall strength of the floors and ceiling of many motorhomes is accomplished by a "sandwich" veneer of foam, or honeycomb board - and plywood veneer - often all glued together. Winnebago has a patent on their combo although I see nothing unique about it.

[jolandua]

Hi, jdemaris. Thanks for the reply. I have continued researching this, and tentatively conclude the best solution is injecting epoxy resin between the laminations and clamping the assembly while the resin sets. There were several posts on a UK-based Caravaning Forum about this method. I looked on Winnebago's site for some advice/information but found nothing (no surprise . . .), and the parts list I have is not specific as to the floor material construction. I can see an Al sheet on the underside and plywood on top. the roof lamination seemed to be Al, then a polystyrene sheet; I saw no plywood (viewed at the reefer chase vent). Guess I need to disassemble a bit more (toilet?) and look for other components in the floor assembly. I have to wonder about the potential effect of injecting the resin on top of a plastic layer in the assembly.

RE clamping the assembly during setting, I had thought I would drill holes through the floor and through-bolt to a plate of some sort on the bottom, which I would remove when done. Then I have to seal the bolt-holes. Any thoughts?

[Derek up North]

Rather than drill holes for bolts, I'd just run some screws through to pull everything together. You could either remove the screws or cut the ends off with a Dremel.

BTW, do you have a link to the UK Forum you mention? I always enjoy how people tackle things elsewhere.

[WME]

If you do use bolts, just drill out the hole to 5/16 or so and get the same size dowel. Coat it with epoxy and stuff it in the hole. After things set up cut off the part of the dowel sticking up

[jolandua]

Thanks to all for your thoughts.

Derek, sorry, I have no link - did not bookmark it - but my search key words included "motorhome", "delaminated plywood". Google presented me with the UK-based forums in the response, along with this one.

WME - closing the bolt-holes with epoxy-impregnated/coated dowels (etc.) is a great idea! I was thinking of leaving the bolts in place, having liberally applied sealastic beneath fender-washers. And just putting up with the tripping hazard as there are plenty of places to grab hold of in the camper ;-).

Onward . . .

[Derek up North]

I just did a Google search. Advice found on Page 1? "We stared at the existing delaminated plywood and decided to drink beer." Sounds British enough to me!

[zero]

. . . my search key words included "motorhome", "delaminated plywood". Google presented me with the UK-based forums in the response, along with this one.

WME - closing the bolt-holes with epoxy-impregnated/coated dowels (etc.) is a great idea! I was thinking of leaving the bolts in place, having liberally applied sealastic beneath fender-washers. And just putting up with the tripping hazard as there are plenty of places to grab hold of in the camper ;-).

Onward . . .

I'm wondering what you are calling "delaminated plywood?" I haven't seen your situation obviously. Just about all the RV floors I've worked on that had soft-spots had rot. Not "delamination" in the strict connotative sense of the word. Delamination denotes the plies separating due to glue failure. Like what happens when plywood with interior glue gets wet. I don't know what plywood Winnebago uses on floors but I'd suspect it's X grade (with exterior waterproof glue). What I find is usually the converse. Glue is still there, but the wood veneers that were once laminated together with that glue are rotted and separated.

Like I said - I haven't seen your situation. If it is rot problem and not a glue-failure issue - I would not try to patch it with some sort of epoxy injection. I'd dig into it, get all the rot and moisture out and put in some new wood. I'd bond it to foam with epoxy. I've been using marine epoxy for years in boat building - either medium set or slow -set.. I've never experienced enough heat to damage any foam. For any epoxies I've worked with - the "exothermic" heat generated by the initial stage of curing epoxy can be as hot as 350 degrees F. Styrene foam melts at 220 degrees F. But epoxy heat is not an issue unless there's a lot of it. I.e. thin layers of epoxy - like if used to bond new plywood to foam - will not get hot enough to damage that foam. If you just pour it in and get any areas over 1/4" thick - then the temps rise at first cure. You can play around with slow-cure, medium-cure, or whatever. But epoxy will "heat itself" and get real hot if too much is in one area. If I had to pour epoxy into deep and large voids and foam was nearby - I'd make sure some sort of filler was mixed with that epoxy to keep the heat down. I.e not pure epoxy being poured in.

There are many epoxies made and marketed for repairing rotted floors in boats. Not much different in RVs if that's what you want to do. In those I've worked on in RVs - observed rot is usually just the "tip of the iceberg." Water imbibes through wood and if you have recent rot damage - it's likely there is trapped moisture in there. I'd tear out what I could, put some heat lamps on it and not try to fix until dry. I just tore one apart that was in inside storage for 4 years. Yet when I tore it apart it was still very wet inside the floor. There is little to no venting and once wet - those areas often stay wet and rot slowly.

Here's a description of one of many epoxy products made for floor rot. I'm not recommending it. Just showing it as one example of many.

"Smith's Clear Penetrating Epoxy Sealer (CPES) consists of a tough, flexible resin system in a solvent blend, and is used to aid in the restoration of rotted or deteriorated wood.

The epoxy resin system chemically adheres to the wood fibers and significantly strengthens them while allowing for normal expansion and contraction.

CPES is effective because it contains a special blend of solvents that penetrate deep into wood cellulose and fibers. When applied to rotten wood, Clear Penetrating Epoxy Sealer changes the cellulose (which the bacteria and fungi find easily digestible) into epoxy impregnated cellulose that resists fungi, while reinforcing and restoring the wood."

[jolandua]

Great information on using epoxy and some specific products to kick off the rest of the research. jdemaris - thanks for the specific experiences regarding your typical findings when checking "squishy" floors. There is evidence of water infiltration or water system leakage in the form of dark discoloration all around the edges of the "delaminated" area - mostly beneath reefer, cabinets, lounge, etc. Also, I can't see it well (no components removed inside yet except carpet), but at the base of the exterior wall there seems to be "a little green". The color of the squishy area in question, between the sink and reefer, is that of a sound top layer of plywood veneer (except it's sort of bubbled up), which is why I tentatively concluded it was simply delaminated rather than rotting. So, I'm thinking I need to accept that pretty much the entire floor needs to be replaced (or at least all cabinets, appliances, etc. removed to get a good fix on the floor ?) . . . yikes! Talk about project scope creep! I'll finish up the father-in-law bathroom project before I tear into this one ;-). It will be informative to cut down into the plywood and have a look. I'll make that the next step. Meanwhile, she is under the RV canopy and at least not directly exposed to our PacNW rains . . .

Cheers! Thanks for responding.

[zero]

Here's my most recent experience with "what you see is just the tip of the iceberg."

My 1988 Mini-Cruiser. We camped with a a few weeks ago and all was fine but . . some sag in front from the sleeper over the cab. Also inside the same area - some slight softness in some of the plywood.

I pulled it apart today getting ready for a trip to North Carolina. What a mess! 100X worse the it looked (as is often the case).

I'm kind of amazed that the main "crossbeam" support where the sag was - is just a nominal 1" X 4" X 74" long board. Actual measurement 7/8" X 3 1/2"

I'm going to hunt around and try to find a stronger and more rot-resistant wood. Shagbark or Pignut Hickory is by far the strongest US wood I can get around here. Bubinga if I want to order some African stuff. Kind of hard to find something with bending strength and rot resistance. Black locust or pressure-treated southern yellow pine I guess. The latter though won't be available dry and I don't want to use wet lumber that's going to shrink.

[Derek up North]

How about just using a 5/4 x 6" x 6' pressure treated deck board. I don't know where I'd start looking for these exotic sounding foreign woods you often mention.

[zero]

How about just using a 5/4 x 6" x 6' pressure treated deck board. I don't know where I'd start looking for these exotic sounding foreign woods you often mention.

Yes, I was thinking along the same line IF I can find a dry one that is still straight. Pretty rare to find a piece of treated SYP in lumber-yard that isn't saturated with liquid. I need to find a board that has been in a dry area for at least a year. Those often warp like crazy as they dry unless fastened to something. I need a board that is self-supportive and straight. The other problem with most treated wood is the adverse reaction is has with aluminum which will be against it. That's a big problem with modern ACQ or Copper-Azole treated lumber. Extremely corrosive to aluminum. The good old-fashioned CCA treated lumber of 10 years ago was fine (when treated with arsenic). No corrosion problems but I can't even buy here here in NY anymore. To use treated wood with aluminum - I'd need a barrier between it and wood so the two could never touch and also would have to use all stainless-steel screws (or something else specially treated to endure the chemicals in the wood).

The main issue with this support is "bending strength" rating. A 7 foot span for a 7/8" thick board is a lot to ask for any wood supporting weight. Here are some bending-strength ratings. The original wood looks like it is Ponderosa Pine which is pretty weak even when NOT rotted.

Ponderosa or Jack Pine = 9,900 lbs.

Southern Yellow Pine = 14,500 lbs.

Pignut and Shagbark Hickory = 20,200 lbs.

Yellow Birch = 16,000 lbs.

Bubinga (African Rosewood) = 22,600 lbs.

Black Locust - 19,400 lbs. and naturally rot resistant

We're talking about the need for just one board 7 feet long. So even for some exotic wood - the price shouldn't be a big deal IF I can get it around here.

[Derek up North]

Well, my problem starts with having to translate something like 'shagbark hickory' into French so I can ask for it!

[zero]

Well, my problem starts with having to translate something like 'shagbark hickory' into French so I can ask for it!

Shagbark Hickory grows as far north as southern Québec and Ontario. I don't know what the Canuks call it locally though. Also has common names like Shellbark, Scalybark, Upland Hickory and I'm sure more. It's one of the slowest growing trees in North America. We have one behind our house that was around when George Washington was alive. This one with my little kid standing by - is dated to be a seeding around 1740. 30 years before my great-grandfather was born in San-François-du-Lac in southern Québec. 126 years before the Irish Fenians attacked Canada from New York State. I'm not cutting it down just to fix some Toyota RV.

[jdfrost64]

been building class A and B rv,s for 28 years worked for coachman and forest river. doing a toy mini right now all new wood and reskinning the whole rv plus new over head cab bunk can,t think of any rv using any plywood for sidewalls or roofs or bunk area what u have in yours in the cab bunk sidewalls and roof is .roof and sidewalls and cab bunk are 5.2mm lauan. backer for nose and rear cap uses a 2.7mm laminated to the sheet metal or fiberglass. don,t know were u live .but only place i know u can get right wood for your mini is a rv plant or right from dealer that sells to rv plants the company name is (robert weed wood products) it makes the job easyer and look better useing the right thickness and what was in it when it was built new. sence i live and work in the rv capital i can get anything for a motor home . if i can help give me a call 1-269-591-9834

[zero]

Getting plywood isn't my issue but thanks for the offer. My problem is the main support beams that are 7/8" X 3 1/2" solid wood and 7 feet long. In regard to Lauan plywood in RVs. Yes certainly used by most.That being said many RVs have 3/8" thick fir or pine plywood in the floor and roofs - and not Lauan. All depends on who made it and when. I'll take 1/4" marine-grade 3-ply A/B treated fir plywood (or 3/8") over Lauan anytime if I can make it fit.

I don't know what species wood that original support beams were but they look like Ponderosa Pine. I need something as strong as possible. 7 foot is a very long span for a wood supporting beam that is only 7/8" thick.

[jolandua]

Good discussion moving along here. jdemaris: Jatoba ("brazilian cherry") is dense, very strong, and extremely rot-resistant. I used (am still using) stakes made from scraps after installing flooring 11 years ago for gardening - not a spot of rot anywhere after staking plants for those years. Might work for your structural support. Another idea: an Al tee extrusion, or two Al angles welded along the top, with plywood fastened on either side.

I was surprised not to see more angle bracing used beneath the floor of my "new" Toy.

jdfrost - thanks very much for your offer re playwood. I'm taking Derek's distaff advice (from somebody in GB) and I'll have a beer and think about what's next. Meanwhile, I'll camp with a "squishy" floor. Nice summer in the works hereabouts.

I would love to see photos of your current work for good ideas.

Meanwhile, folks, I will get some photos of my little jewel together so's we can share ideas and expertise with visual aids (thanks for your photos jdemaris!)

[jolandua]

Today, explored this problem again and now have a repair plan.

I drilled a hole through the "delaminated" plywood, and found it's not (delaminated plywood, that is). jdemaris, correct as is usual! Some photos included with this response. The ~1/4" plywood is sound, but separated from the foam and bowed. When I bought this, the previous owner had never removed the plastic cover stapled over the carpet (which I did . . .). Because this bowing occurred only in places that were covered with plastic (no bowing directly under reefer, though "water marks" are on edges of the bowed flooring just next to the reefer - last 2 pics), I now wonder if somehow that caused the plywood-to-foam bond to fail, and the subsequent bowing.

I decided to move on in a different direction than trying to re-laminate the plywood and foam using epoxy. This, because it does not seem to me that I can get a good enough "squeeze" during the epoxy set without screwing or bolting through the laminations anyway. Also, I want to stiffen the floor. So, I elected mechanical strengthening beyond gluing.

I plan to install back-to-back AL channels (1/2"x2", 0.125" th), one in the cabin, one beneath, bolting through the existing floor plies. Then, I will install 1/2" and 3/8" marine AB plywood on top of the existing floor, gluing and screwing the 1/2" to the existing plywood, and filling the floor-top channels in with the 3/8" to keep the floor flat and hide the bolt-heads. I think this will stiffen along the cabin axis and strengthen side-to-side too.

I'll send more pics when there is further progress.

[zero]

I wish marine-grade plywood wasn't so d*mn expensive where I live. Night-and-day difference though over common construction grade pine plywood with less plies and weaker wood. Last few sheets I bought of 3/8" marine was 4-ply and made from Douglas Fir. MUCH stronger then 3/8" 3-ply pine from the local lumber yard. I use it on cabinet doors also. Much less apt to warp.

[snail powered]

been building class A and B rv,s for 28 years worked for coachman and forest river. doing a toy mini right now all new wood and reskinning the whole rv plus new over head cab bunk can,t think of any rv using any plywood for sidewalls or roofs or bunk area what u have in yours in the cab bunk sidewalls and roof is .roof and sidewalls and cab bunk are 5.2mm lauan. backer for nose and rear cap uses a 2.7mm laminated to the sheet metal or fiberglass. don,t know were u live .but only place i know u can get right wood for your mini is a rv plant or right from dealer that sells to rv plants the company name is (robert weed wood products) it makes the job easyer and look better useing the right thickness and what was in it when it was built new. sence i live and work in the rv capital i can get anything for a motor home . if i can help give me a call 1-269-591-9834

I can buy 5.2mm plywood at my local lumber store. I just used my calipers to confirm that is the actual thickness of the pieces I have been using.

[zero]

Last RV interior I did (this past summer) was with 5.2 mm "underlayment" hardwood-plywood from Home Depot. It's what they were selling at the time in place of a Luan-based 1/4" underlayment. It's made in China from Chinese or Russian white birch and with exterior glue. As far as I can test - it is far superior to any Luan-based plywood I've ever used and was dirt-cheap. But there have been many efforts to block the so-called "unfair" competition from China and I have no idea what Home Depot is selling now. It seems to change on almost a daily basis.

The wood I got was good enough for cabinet work even though it was sold as underlayment. I tested pieces in a washing machine for delamination and got none It passed my crude tests 100%.

[WME]

I used the underlayment wood when I redid the floor in my Escaper. The sheets I bought had one good side and 2 more plys than "normal" plywood.

I sorta built a Sunrader floor. I stripped out the carpet. Then glued down a 1/2" foil faced foam sheet. Then glued and screwed the underlayment over that. Then vinyl flooring. A lot quieter, warmer and way stiff. Surprisingly the lower doors worked with out trimming. I lost less than 1" of headroom

[jolandua]

I've been using pieces of the same Home Depot underlayment ripped into 3" strips to stir, apply, and clean up thinset mortar through the summer. No delamination there either. Who knew I was testing materials for Toyers? Great stuff. ;-)

[zero]

That's funny. I was also using scraps of the same plywood to apply thinset mortar. Not as a test. Just saved me some clean-up of tools when done.

[jolandua]

The installation outlined earlier is complete now, except for final flooring (will it be vinyl or "hardwood" or carpet? Only my boss knows, and she hasn't told me yet . . .) The floor in the modified area is very stiff. Now I can tell how spongy the rest of it, forward of the repairs, remains.

Here's a photo of the completed set up, just before gluing down the 1/2" AB Marine (the lighter colored stuff).

Used this convenient epoxy dispenser and spread the epoxy on the plywood using one of my small drywall knives.

The plywood pieces just before I laid them in place.

And here's what the bolted in channels look like from beneath.