Marine Grade Plywood or Coosa Board That is the Question

[Foiled Again]

Well Re-Pete lives in Virginia Beach, VA and the area is home to the Atlantic Fleet and Chesapeake Bay. LOTSA marine businesses, so finding Coosa here is easier than most places. If you are based in Arizona.... well leaks in the desert just aren't that frequent. Others might benefit by getting a WBCCI group purchase, or taking a utility trailer to the nearest big saltwater port.

[David F]

Let's don't forget that Marine plywood rots just as easily as other plywood. Marine grade only makes the plywood a structural grade plywood in that it does not have voids in the plys and waterproof glue is used. Exterior grade plywood has the waterproof glue, but is not a structural plywood. How much that matters is uncertain to me, but I would use a good quality exterior grade plywood (i.e. BCX) and call it good after sealing the edges at the perimeter well.

[skyguyscott]

Yes, Coosa Board is expensive. It is much more expensive than any flavor of plywood. But don't forget the cost and trouble of replacing the flooring, up to and including a shell-off project. Materials, Labor, Time, Trouble, plus the stink of rotting or infested plywood while you wait to get it fixed....

By my accounting, only ever having to do that once with Coosa, as opposed to as much as every 10 years (yes I know some trailers are stored inside and only get out a few weeks a year, and the plywood has lasted 50 years) is more than worth the extra cost in materials.

And if you think you can keep your AS from ever getting water on the floor, well, you are a better camper than me.

[PKI]

1) Store the trailer inside.
2) Keep the trailer sealed.
3) Keep the trailer waxed.
4) If you like fixing AS trailers - use whatever you want, because you will not find floor replacement of any consequence. Tight budget refurbs will likely need to take the plywood/epoxy seal approach, as there will be many compromises required to limit the expenditures for your repairs.
5) If you recognize how expensive and difficult the replacement of an AS floor is and plan to keep your coach forever, use the best = Coosa or aluminum plate on an aluminum frame.
6) Trying to get someone else to pay for your extravagance is likely going to be difficult. Think fast sale for a reasonable price or a long time looking for someone who wants what you did and has no interest in doing it themselves, but has lots of money. Better upgrade everything else ... wiring, electrical fixtures, plumbing, furniture hardware, storage convenience, DC components, work surfaces, mattress, cushions, upholstery, solar .......as well. Note - if your skills are not professional, and your implementation is not flawless, the value add will be greatly reduced.
7) Just my opinion and yours counts a factor of 10 more, so think on it a bit and enjoy the renovation adventure. Pat

[skyguyscott]

Originally Posted by PKI

1) Store the trailer inside.

(Yup, but how much does that cost, assuming you don't already have a barn, large shed, own a storage facility?)

2) Keep the trailer sealed.
3) Keep the trailer waxed.

(Certainly, but how often, once or twice a year? How much in labor and materials for that?)

4) If you like fixing AS trailers - use whatever you want, because you will not find floor replacement of any consequence. Tight budget refurbs will likely need to take the plywood/epoxy seal approach, as there will be many compromises required to limit the expenditures for your repairs.

(It was pretty consequential for me, having to remove lots of interior furnishings, etc.)

5) If you recognize how expensive and difficult the replacement of an AS floor is and plan to keep your coach forever, use the best = Coosa or aluminum plate on an aluminum frame.

(Yeah, I am not one to buy and sell 5 different AS over my lifetime)

6) Trying to get someone else to pay for your extravagance is likely going to be difficult. Think fast sale for a reasonable price or a long time looking for someone who wants what you did and has no interest in doing it themselves, but has lots of money. Better upgrade everything else ... wiring, electrical fixtures, plumbing, furniture hardware, storage convenience, DC components, work surfaces, mattress, cushions, upholstery, solar .......as well. Note - if your skills are not professional, and your implementation is not flawless, the value add will be greatly reduced.

(Maybe. I have found rotting floors to be among the most common AS problems. (I don't consider offensive interior decorations a "problem" but certainly an annoyance) Can you recall a more common problem that is not the result of a soft or rotten floor? Dents maybe? The $#% suicide door?)

7) Just my opinion and yours counts a factor of 10 more, so think on it a bit and enjoy the renovation adventure. Pat

(That's why we're here, to discuss and offer options on everyone else problems)

[rmkrum]

Originally Posted by skyguyscott

(That's why we're here, to discuss and offer options on everyone else problems)

Oh, AMEN to that--some days its the absolute best diversion from the day-to-day dealing with our own problems of all sorts.

Besides, it's real good writing practice and mental exercise for us Old Pharts...that can certainly use some sort of exercise!

[fastrob]

Originally Posted by Re-Pete

.................................................. ........................................ I'm fortunate because it's available from a local distributor, so shipping costs are not a factor which is a nice plus. I'll need about 7, 4' x 8' sheets. I believe I was quoted $275 per sheet. So yeah, expensive, but I didn't tear this thing down to the ground to skimp.

I checked locally, in Maine, and the price was $345 plus 5.5% tax per sheet.

[AlumiDillow]

So I am doing a full retro and I considered coosa and I decided against it because I understand you can't just put a screw in Coosa. You have to drill a hole and fill it in fiberglass or something in order for the Coosa to have any holding power. That seems like a lot of extra work. And its not that I mind the extra work but I would not want to put in the 1000s of hours needed to do the full shell off and then find in a few months or years that screws are coming loose and I have to do it again. Plywood is tired and true.

[Aunt Bea]

Originally Posted by Isuzusweet

If you have gone as far as what you have shown......Coosa is a no brainer; and like I stated, you'll get your money back and more if you sell her and state you have Coosa as a subfloor; it just tells people you didn't scrimp on your renovation, and you're not hiding anything.

Cheers
Sidekick Tony

Personally I would use pressure treated plywood. Pressure treated ply is rated at 40 years with ground contact. Marine ply uses water proof glue to laminate the ply's but does nothing to preserve the wood itself. Various ply's are available as well as various ground contact ratings. Aunt Bea

[GMFL]

Slow down now.
Pressure treated plywood may not be a good idea.
The salts and other chemicals used to treat the wood is corrosive and can cause problems with the steel frame and aluminum shell
AND....... the chemicals used in the treating process can cause cancer in the state of California, so you would not be able to safely travel there.

[AlumiDillow]

Originally Posted by GMFL

Slow down now.
Pressure treated plywood may not be a good idea.
The salts and other chemicals used to treat the wood is corrosive and can cause problems with the steel frame and aluminum shell
AND....... the chemicals used in the treating process can cause cancer in the state of California, so you would not be able to safely travel there.

I agree with this. I used marine plywood and sealed the ends with epoxy. I would not want the chemicals from treated plywood in the trailer.

[guskmg]

Cosoa Board can not be screwed. Wrong. I just made a toilet riser out of two 1" pieces of Cosoa board. Screwed them together with marine stainless steel screws. Cosoa board is handled just like plywood. It was a snap to cut out a toilet base shape on a band saw. It is made of a mixture of fiberglass and plastic. Two pieces cand be glued together with Sikaflex 252. The manufacturer recomends oil based paints because water base paints do not adhere good. Also, if left unfinished the fiber glass chards could be a problem, therefore, a resin based sealer is a good solution. I would use it again, in a heart beat, if moisture was a concern.
guskmg

[skyguyscott]

Yup.

If someone told you there was a super material out there that was just as strong as plywood, and just as easy to work with only in addition it was:

• waterproof
• mold resistant
• critter & varmet proof
• AND acutally 30% lighter weight

You would say, "That's too good to be true! What's the catch?"

The catch is it is much more expensive. The solutions to our problems are often out there, it's just we seldom want to pay for them.

[Gregsch]

I went with Tony's advice 3 or 4 years ago and went with the 3/4" Coosa 26. I am totally convinced it is the way to go. You can't just screw things down like you would screw something down to plywood but, you can't glue 2 pieces of plywood together and make them into one by gluing them together with fiberglass resin either.

For me the final decision came down to this . Do
i want to remove the cabinetry, the interior liner panels, the floor covering, the wall partitions etc... again if there is another leak that goes unnoticed an causes rot. Not on your life, this is on job I never want to do again.

[Philip Jones]

Wow. I am hoping that if I ever buy another Airstream the factory will have elected by then to just use Coosa. Seems like a no-brainer for such an expensive trailer. And, for such a vulnerable area of the trailer.

[Isuzusweet]

Originally Posted by Philip Jones

Wow. I am hoping that if I ever buy another Airstream the factory will have elected by then to just use Coosa. Seems like a no-brainer for such an expensive trailer. And, for such a vulnerable area of the trailer.

You would think that would be a no-brainer.....but Thor is only interested in putting money into bling that will bedazzle buyers into thinking they're buying a top of the line luxury trailer that will last a lifetime.......subfloors are just not sexy enough.

To answer a previous poster; yes, Cossa may not be the best material to hold a screw, BUT I've screwed (and unscrewed every winter) my water pump in the same holes into the Coosa without a problem. You could reinforced the screw hole by screwing in a lead drywall plug screw; or something like that.

Where there is a will, there is a way; and if that's the only problem with Coosa I face.......I'll take it any day.

Cheers
Sidekick Tony

[Re-Pete]

The Coosa rep did tell me they did not recommend using screws to fasten things down to the Coosa, but screwing through to say a backer of some kind was fine and through bolting was fine . I believe he did mention some other ways. I'll just need to call them back and ask. We did not discuss seaming two pieces together, but I will follow up on this as that sounds like a good idea. Additional good news is that I miss remembered the price I was quoted from the local distributor. We spoke about a few things that morning. Stopped by there today and learned I'm paying $216 per sheet of 3/4" (actually 19mm) x 4' x 8' of Bluewater 26. So, even with a sales tax of I believe 6% I'll get away with just a bit over $1600.

I'm pretty tickled with that. I gave them my credit card and locked it in.

[Isuzusweet]

Originally Posted by Re-Pete

I'll just need to call them back and ask. We did not discuss seaming two pieces together, but I will follow up on this as that sounds like a good idea.

I half lapped my joints....using a router with a 3/4" wing cutter I set up the router to just barely cut over half the thickness of the Coosa. So add 3/8" over center of support beam to a sheet when you cut it. When you fasten the sheet , the fasterner will be in the center of the support.

This process enabled me to A) Have flush joints all the way across regardless of what the gridwork was doing below the Coosa, as the half lap below supported the half lap above; B) By cutting just a hair over, it allowed me to silicone the joint together. C) It also meant that I was fastening down two sheets using only one line of fasteners.

Hope this helps.
Sidekick Tony

[suncoasteng]

On my most recent boat deck project I could not find marine plywood. Local plywood dealer suggested I go with HDO Plywood. Attached it with counter sunk screws and coated with three layers of epoxy paint. Boat stored outside and it is now three years on the HDO and still holding up well.

[jcarp]

I am full skin off putting coosa as sub floor. What fasteners did you use and how did you seal the seams