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-   -   pressure treated ply -- not against aluminum! (https://www.airforums.com/forums/f36/pressure-treated-ply-not-against-aluminum-29176.html)

geezernbabe 01-09-2007 12:16 PM

pressure treated ply -- not against aluminum!
 
This might be the second post but here goes. I own 8 sheets of pressure treated plywood. Now that I have read all the stuff here I got to looking at the tags that come stapled to every sheet and in the small print it says not to be in contact with aluminum and I got to thinking that is a real big possibility in this little project. I am sure glad I did some reading here first. Thanks Dave

markdoane 01-09-2007 12:42 PM

Dave,

Bad news, but at least you caught it before you screwed it down.

Do you have someplace else you can use the green stuff?

geezernbabe 01-09-2007 12:48 PM

green stuff
 
Boy that sounds like something bad. I just retired from being a carpenter for 30 years so I have lots of places to use it. I worked with pressure treated wood some a I do not walk around talking to myself to much. I just never used around alum.

VSP Raleigh 01-09-2007 02:37 PM

I'm assuming you're talking about using it on the floor? If so, what about using something between the wood and whatever you are going to fasten it to? Roofing felt perhaps?

geezernbabe 01-09-2007 03:28 PM

Boy I guess I could have said floor. But I guess I was just thinking floor. I probably could but all the the rest of the things I read make it sound like a bad idea. But thanks for the thought.

Fyrzowt 01-09-2007 05:10 PM

Cheaper to use it some place else on another project, than to have something bad occur because of an accidental contact with aluminum.
Does anyone know what the reaction is? Is it a structural issue or a health issue? Some chemical reactions are not worth playing around with.
Dave

markdoane 01-09-2007 05:27 PM

The main problem is corrosion due to the emf of chromated copper against aluminum. I've also heard some people express concern about living on a floor treated with arsenic, but I don't think that is a problem if it is sealed under tile or vinyl.

Turbos4life 01-21-2007 04:11 PM

Most all pressure treated wood for residential use is now ACQ. ACQ is very corrosive on all metals except stainless steel.

Lumatic 01-21-2007 05:16 PM

Pressure treated warping
 
I don't know about ply but regular pressure treated lumber tends to warp more than untreated.

rmpray 01-21-2007 05:49 PM

I've used fire rated ply (surplus) on different projetcs, but not my AS. Thing is, even pieces I badly neglected, leaft in the weather for a very long time, seems to hold up remarkibly well. Not pressure treated but apparantly uses an epoxy glue. Never say any warning tags on it either. Eats saw blades, but once cut with a well lubricated say it is tuff. I wonder how it would do?

boatdoc 01-22-2007 04:53 AM

Pressure treated plywood.
 
Quote:

Originally Posted by geezernbabe
This might be the second post but here goes. I own 8 sheets of pressure treated plywood. Now that I have read all the stuff here I got to looking at the tags that come stapled to every sheet and in the small print it says not to be in contact with aluminum and I got to thinking that is a real big possibility in this little project. I am sure glad I did some reading here first. Thanks Dave

Hi Dave; We have in the past tried to use it in aluminum boats as flooring. Bad news. First of all, it did de-laminate and surface cracked as it dried in hot sun leaving us a great mess to re-do. That process of drying oxidized the aluminum surface as well. To top it all, using it on the floor in confined space such as your RV it is something I would not think of doing.
I do not believe that is possible to make it air tight.
This stuff is treated against rotting but not de-laminating and cracking.
I just finished a new SS frame and new floor. I have used Omega Panel board. It is 1/2" thick, and both sides are laminated with 0.025" aluminum sheet, making it into a very stiff 4x8' panel. Cut edges were heavily flooded with Git Rot and trimmed with 1/2" C channel, sealed with 3M 5200 adhesive. My intention was to do it once and forever. Cost of labor is many times greater than the difference in material costs. Thanks, "boatdoc" :lol:

rickandsandi 01-22-2007 07:19 AM

Yuk!
 
Greetings Dave!

Yes, pressure treated ply is a cancer for AS. Stick to 5/8" marine ply. Another problem I have heard of with PT ply is that is never really dried when shipped to the yards hence the shrinking, delaminating etc. As with ALL PT lumber as I am sure you know always were a mask! Pretty yukky stuff to be breathing in.

boatdoc 01-31-2007 06:22 AM

Marine Ply vs Exterior Ply
 
Quote:

Originally Posted by rickandsandi
Greetings Dave!

Yes, pressure treated ply is a cancer for AS. Stick to 5/8" marine ply. Another problem I have heard of with PT ply is that is never really dried when shipped to the yards hence the shrinking, delaminating etc. As with ALL PT lumber as I am sure you know always were a mask! Pretty yukky stuff to be breathing in.

Hi rickandsandi; I thought that I should just mention the differences between Marine and Grade A exterior plywood.
Glue used in exterior ply is the same as one used in Marine ply.
Marine ply is mostly Luan veneer filled with Mahogany or Luan outer. Major difference is in the quality of veneer. Marine ply has no voids or cracks in fill veneer, exterior plywood does to some degree. Grade A exterior is usually one side sanded and has no patch work on the clean sanded side. While it is difficult to find a good grade of exterior, few company's produce it, where voids inside are almost non existent. Use of Marine plywood as floor in AS is almost cost prohibitive vs Grade A exterior which is half the price. The most important issue with floor is sealing it from moisture which will rot marine plywood as quickly as exterior. PC- Products has on the market a wood petrifier in a liquid form which we experimented with. We heated the ply to about 80 degree for 12 hours and soaked the ply with it. Two samples from the same sheet were placed outdoors for four months, one treated one was not. Untreated ply showed serious deterioration while the treated piece looked as the day we left it. While we have no proof of further longevity the stuff worked very well. Perhaps this may be a cheaper choice for floor replacement. Thanks, "Boatdoc":brows:

rickandsandi 01-31-2007 06:32 AM

Greetings Boatdoc-

Your comments are right on, but when it comes to my AS projects nothing is too good! The few extra $$$ make for a job done that will last longer than I. While there is often a less expensive way to do things that may work, I would rather put my money into the best whenever possible. Thank you for sharing your input!

Rick

2333 05-09-2007 06:00 PM

Re-open thread....
 
The Mods seem to recommend that it's better to tack onto an existing thread than start a new one, so I searched the forums and this thread seemed appropriate.

Well I am down to a bare rusted frame and I ordered 4 quarts of POR-15 and both the Marine Clean and Metal Prep....

Now, for the choice of floorboard. I know not to use any ACX, ACQ, or pressure treated wood in direct contact with almost any metal (thank you forums). But, won't POR-15 help solve this dilema?

1. If the wood sits on a POR-15 coated frame...
2. If the U-Channel sits on vinyl tiles (which cover the whole floor)...
3. If the edges of the subfloor are treated with resin for "waterproofing" (thus when the belly pan wraps up and around the U-Channel it doesn't directly contact the wood)....
4. If I use stainless steel elevator bolts and screws....

Then have I eliminated the concerns about corrosion associated with these products and metal?

crestonrv 05-11-2007 08:45 AM

pt is not recomended for interior work,out gassing. it's poison!!!.

2333 05-11-2007 09:25 PM

Got it...
 
Thanks crestonrv, I knew that about PT. I had a deck that the kids played on for about 4 months before I began dismantling it and found the little tag on the end stating "ARSENIC - Write your will". But I digress.

My research into ACQ is that off-gassing is not an issue, but that when used in contact with soils, etc. it has the potential to leech and may harm earthworms and aquatic life.

I'm not trying to support the use any particular option here, just getting opinions on whether it's feasible to use in the manner I previously stated.
Appreciate the feedback!

malconium 05-16-2007 12:31 AM

I think that you are probably right that you might very well be isolating the pt plywood from everything else using the techniques that you mentioned. But I still think it is not a good idea. I replaced all of my subfloor with pt plywood of the new variety which supposed is not particularly toxic any more. Just after I finished the job I found out just how corrosive it was. I had installed it in contact with the aluminum in the c-channel at the bottom of th u-channel (different construction than for your vintage). When I took it all out I could already see signs of corrosion in just a matter of a couple of weeks at the most. I just think the stuff is too corrosive to bother with. I would suggest that a reasonable alternative might be to carefully saturate/coat a good grade of plywood with Thompsons Waterseal. It is not considered by the manufacturer to be toxic once it is fully dried (I asked them directly). What I decided to do was to use a product called Polyboard but that is another story.

Malcolm

ZoominC6 05-16-2007 05:39 AM

Advantek
 
For anyone considering replacing the subflooring of their Airstream during reconstruction I would seriously consider ADVANTEK FLOORING in lieu of any marine product. This is a superior product that WILL NOT delaminate, swell or rot. It is a bit heavier than marine grade plywood and more expensive but worth the price in my estimation. Any good lumber yard can give you information or you may GOOGLE it.
Happy Trails! :flowers:

2333 05-16-2007 12:06 PM

That Advantech does look good, but now trying to find someone who carries it is going to be fun!


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