floor repair: Tyvek over plywood?

[Bob Blarney]

I'm considering materials for floor repair. While Coosa board or Thermo-lite seem to be the materials of choice, if plywood could be made more water resistant (or 'waterproof') then it could be very cost-effective.

When I was thinking about building my flyweight tiny 'Foamie' trailer, I did some adhesion tests for bonding Tyvek to extruded polystyrene foam insulation. My objective was to employ the light weight, tear, and puncture resistance of Tyvek with the insulation to make suitable wall and roof panel, but the water barrier properties of Tyvek was not a consideration. But Tyvek might be a useful material for protecting a plywood floor in an AS.

Liquid water does not pass through Tyvek, but water vapor can pass. If it were bonded to ACX plywood (~$30/sheet), then it would protect the plywood from a soaking leak yet allow any water that did get through to evaporate. There remains the issue of sealing the edges and holes around the perimeter, perhaps epoxy or rotproofing treatment in those areas would work.

Does anybody have opinions of this idea?

BTW, if you're wondering about the Foamie tiny trailer, in the end I scored the foam with a ripsaw blade, applied Titebond III waterproof glue (10% diluted) with a paint roller, and placed 10oz. (not pre-shrunk) canvas. As the Titebond III cured, the canvas shrunk down tightly and formed what is known colloquially as 'poor man's fiberglass'. It was then painted with Glidden Gripper and a high quality exterior latex paint. For me, the non-toxic nature of the materials was very important; I didn't want exposure to fiberglass and resin, as well as the job of sanding the cured fiberglass.

[Isuzusweet]

Unless you replace all the organic material in plywood with an inorganic material, it will never be waterproof.

It's like putting lipstick on a pig; takes a hellova lot of effort, and for what? Save a few bucks on a subfloor you've spent days taking out and more days to replace?

Spend the money on Coosa and never have to worry about it again. The money you spend on Coosa will be recouped if you ever sell the trailer as you will be able to show a prospective buyer, you cared enough to put the best product into your rebuild, and why you are asking what you're asking.

Peace of mind is priceless.

Doesn't that make sense?

Cheers
Tony

[Bob Blarney]

Originally Posted by Isuzusweet

Unless you replace all the organic material in plywood with an inorganic material, it will never be waterproof.

It's like putting lipstick on a pig; takes a hellova lot of effort, and for what? Save a few bucks on a subfloor you've spent days taking out and more days to replace?

Spend the money on Coosa and never have to worry about it again. The money you spend on Coosa will be recouped if you ever sell the trailer as you will be able to show a prospective buyer, you cared enough to put the best product into your rebuild, and why you are asking what you're asking.

Doesn't that make sense?

Cheers
Tony

In any thing, cost versus performance is always a factor. Coosa Board is about 8x the cost of plywood, and that is not insignificant. Coosa Board does provide structural integrity, but it would not protect the finished floor or carpet from water intrusion, nor prevent anything that may grow in water-saturated insulation. It is not a substitute for regular maintenance of the trailer's exterior. Also, it may or may not add anything to the resale value of the trailer. That money could be spent on other improvements.

When protected from constant exposure to both water and oxygen, wood can last for centuries, whether it is in a desert, as structural beams of my house, or buried underground as a water pipe, or as the deck of an Airstream. While not at all desirable, occasional exposure is not a structural problem with plywood.

In the AS as built in the factory, there is the 'engineered' problem of inevitable leakage at the seams, rivets. windows and roof penetrations, and it is compounded by the overlying materials - padding, carpet, and that plastic carpet protector that was unnecessarily left behind during assembly, and possibly insulation that prevents evaporation of the absorbed water.

So, maybe I'll do a test over the winter, by bonding Tyvek to a 2'x4' piece of plywood, and see how it does outside exposed the winter's snow and rain. I might use a moisture meter to collect data. For this period of time, deterioration of the Tyvek from UV light is probably not a significant factor.

[perryg114]

Wood is fine if it is seal on the top and around the edges. BIGGEST mistake that is made is to cover the floor from wall to wall then put the stuff back in. This makes it impossible to keep an eye on the floor and also holds the water in to guarantee rot. Water is not the problem so much as it not being allowed to evaporate. Plan on stuff getting wet and figure out how to mitigate that. I put in C-channel drains and sealed it to keep as much water off the floor as possible. I am an advocate of a bare floor what is urethaned or at least carpet squares on top that, that can be pulled up. Also getting rid of insulation that either stays wet like fiberglass or the bubble wrap stuff that traps water. Boats stay in water and last for decades if treated properly.

Perry

[Bob Blarney]

And here's the Product Manual from DuPont.

http://www.dupont.com/content/dam/du...t_Handbook.pdf

[GeocamperAS]

At 35 years old , 1978 Argosy, I did a shell off floor replacement. The original was unprotected plywood. The amount of rot seemed to be in order with many others on the forums. I figured if unprotected plywood lasted 35 years, new plywood sealed with primer and paint would last for at least another 35 plus.

[bradt]

Here is an industry article that addresses moisture control in buildings from a "properties of water" point of view. Even though it deals with buildings, the issues are the same. I have read this about 6 times while thinking about my Airstream. There is a lot that speaks to the moisture issues we have.

https://buildingscience.com/document...sture-problems

One thing that applies directly is the use of vinyl coverings, which are unintended vapor barriers. We have vinyl floor covering and rotting floors. The hotel industry got the idea to use vinyl wall coverings since they are easy to clean and scuff resistant. Then they had rotting walls that smelled of milldew.

The mechanisms of how moisture travels horizontally via wicking and up and around by vapor pressure help explain some of the things we see. Often, opening areas so they can breathe is the answer instead of sealing them up.

The example of the intake air flow for the HVAC systems applying suction to pull moisture laden air into the walls made me think of my rooftop AC unit. I checked, and sure enough, the rough cutout thru the AS roof is not boxed in and sealed. So when I run the AC, it is open to suck in air from inside the walls. This can be easily fixed.

This article seemed to present examples of serious unintended consequences of construction methods that otherwise appeared to be thoughtful and accepted practice. I think that is the situation with the moisture problems our Airstreams have. Lots of good quality materials, put together in a way that inadvertently trap moisture.

Brad

[TouringDan]

Bob

I don't think Tyvek will work. It works on houses because it is on a vertical wall with only small penetrations from fasteners. In a horizontal application you will not be able to seal the penetrations to prevent water from getting to the wood.

I have recently completed floor repair in my 66 Tradewind. The entire floor was dry and undamaged except for the rear 12" which was rotted out. The floor repair is shown in photos 1 & 2. All floor repair was completed from the bottom as the gray water tank and banana wraps had been removed. I believe the cause of the floor rotting was the infamous poor design of the bumper trunk front top piece that allows water to flow between the front top piece and the cross member and then wet the bottom of the floor that touches it (photo 3 shows the old front top piece and the new front top piece). To keep the new plywood from rotting, if/when it does get wet, I sealed both sides of the plywood, the edges and all the penetrations as well as I could. I then caulked the joint between the exterior rear wall covering and the bumper trunk front top piece using TremPro 635 (photo 4). I believe keeping this joint sealed is the best thing we can do to prevent floor rot.

Dan

[Bob Blarney]

Dan, thanks for your contribution. Your point about vertical versus horizontal positioning is well taken, although I was not considering the use of penetrating fasteners. I was thinking about using an adhesive that is compatible with Tyvek but that does not form a vapor barrier. Surprisingly, DuPont says that animal hide glue is an excellent adhesive for Tyvek, and I've made use of hide glue's wonderful properties for furniture and musical instrument construction. But I can't imagine using hide glue in this application. I'm sure that 3M must have a suitable adhesive.

I'm also looking into cork as a finish floor material in the bedroom. It was used in submarines, and I've walked on residential cork floors that are attractive, insulating, and comfy on the feet. But that's further down the road.

[rugjenkins]

Have you considered painting foundation sealer/waterproofing instead?

[TouringDan]

Originally Posted by Bob Blarney

.



I'm also looking into cork as a finish floor material in the bedroom. It was used in submarines, and I've walked on residential cork floors that are attractive, insulating, and comfy on the feet. But that's further down the road.

Bob

I installed a cork floor in my Tradewind.
You can see photos if you look at post 4 of my thread Dan’s 66Tradewind Improvements.

Dan

[Bob Blarney]

Originally Posted by rugjenkins

Have you considered painting foundation sealer/waterproofing instead?

Do you mean a mortar-based paint such as DryLok? I wouldn't want something that is waterproof, because it would trap water that had penetrated. I want to first stop liquid water from being absorbed in any significant amount, and yet allow water vapor to escape- that's the selling point of Tyvek.

[Bob Blarney]

Originally Posted by TouringDan

Bob

I installed a cork floor in my Tradewind.
You can see photos if you look at post 4 of my thread Dan’s 66Tradewind Improvements.

Dan

It looks good! Has the cork lived up to your expectations for comfort and durability? I've been mulling over square tiles vs snap-lock t&g planks as you did. I was thinking that tiles would be easier to place, and replace individually if needed.

[TouringDan]

Originally Posted by Bob Blarney

It looks good! Has the cork lived up to your expectations for comfort and durability? I've been mulling over square tiles vs snap-lock t&g planks as you did. I was thinking that tiles would be easier to place, and replace individually if needed.

We really like the cork floor. It feels real good and has held up well after 5 years except for a couple of locations where it has gotten wet. Like a lot of flooring material it swells up pretty good if it gets wet. I will need to replace a few pieces of flooring. We will see how this goes. If it does not look good, we will replace the entire floor covering. One nice thing about the floating floor is that I can probably remove all of it in 30 minutes.

Dan

[Airtandem]

What about Tyvek UNDER marine plywood?
MJ

[J. Morgan]

I think bonding the Tyvek would ruin its ability to pass air.

[Bob Blarney]

Originally Posted by Airtandem

What about Tyvek UNDER marine plywood?
MJ

There seems to be some misunderstanding about marine plywood versus regular construction plywood. Originally, only marine plywood had waterproof glue holding the laminations together, but nowadays all plywoods have waterproof glue. The other major differences with marine plywood are that it is guaranteed to have no voids and is usually made from tropical woods that have a smoother & better appearance than construction grade. But marine plywood is no more resistant to rotting than regular plywood during constant exposure to fresh water. Strengthwise, regular plywood is plenty strong enough for the subfloor. So I'll save my money.

[Bob Blarney]

Originally Posted by J. Morgan

I think bonding the Tyvek would ruin its ability to pass air.

Did you mean passing water vapor or air? Tyvek blocks air, but not water vapor. For bonding Tyvek, a thin glue layer that is not extremely resistant (or waterproof) to water vapor would be needed. I've been looking at glues, and it may be that Elmer's School Glue would be suitable. It holds materials together, but releases from clothing when it is subjected to the rigors of hot soap and water in a washing machine. That suggests to me that water vapor should pass through. Also, regular Titebond aliphatic (yellow) resin glue is resistant to water but it is not waterproof, hence the development of Titebond II (much more resistant) and Titebond III (totally waterproof).

[Jeremiwvu]

The only way to prevent rot is to prevent moisture. It is also important to prepare for the inevitable leak.

To prevent moisture the best policy is regular inspection and maintenance of the exterior. One factor not considered is mold. Even if you prevent the rot by keeping up with exterior waterproofing we all know you will have a leak occasionally.

My wife has a severe mold allergy, we had issues in our old airstream and had leaks in our current one when we bought it. We replaced floors and consulted a mold mitigation specialist with how to treat the existing plywood, they recommended kiltz primer and said it is the only product they use to prevent mold. We painted the floor with it and installed the new floor in such a way that we can check under edges for moisture and stay on top of exterior maintenance.

Bottom line is no matter what products you use (even expensive ones) that you should install and not be on top of preventing moisture in the first place. Even if the product used will not rot that is only part of the problem. Moisture is a problem even if the plywood substitute won’t rot. There are still structural steel components and other areas that are vulnerable to long term exposure to moisture.

If you had a roof leak in your house which lead to rotten floors the logical solution should not be to replace the floor with a product that won’t rot... same logic applies here IMHO.

I do think that a mold inhibitive paint and primer are more advantageous than tyvec or any other sheet, and it would be much more straight forward installation.

Good luck with the project.

[dmbecke]

Can treated plywood be used ?