Confused about plywood.

[Jeff1226]

Have a question about marine plywood. Is it treated?

 

[5150abf]

Re: Confused about plywood.

Welcme to iboats.

Yes it is treated, I believe with arsnic and other things, if you are usign it on an aluminum boat you want to seperate it from the metal, this can be done with about anything, we use a thin 1/16'' foam tape at work.

It is a little spendy but worth it, the stuff last forever even out in the elements completely unprotected.

 

[MinUph]

Re: Confused about plywood.

Sorry to disagree with you 5150 but Marine grade plywood is not treated. Pressure treated plywood is not marine grade.
Marine grade is normal layers. The glue is exterior, and there should be no voids in the interior layers.
PT wood would need to be separated from most anything else like aluminum. but not marine grade.

 

[joewithaboat]

Re: Confused about plywood.

As correctly stated above "marine" and "treated" are two different types of plywood. There are many variations of each.

Typically Marine plywood is all about the glue its put together with and the lack of any internal voids in the inner ply's. It usually stays very flat and true which makes it nice to work with.

Most treated plywood is air dried after treating and is miserable to work with. Some manufactures offer kiln drying after treating. It is also not typically made from the better grades of lumber and has lots of internal voids.

Hope this helps!

 

[MinUph]

Re: Confused about plywood.

To add to this. Plywood use to be interior or exterior. In recent years they have started making all plywood with exterior grade glues. So in reality any good grade plywood will suffice for flooring. If you want to use a non marine grade look at cabinet grade plywood and by all means ask about the glue used. A supplier of same will know or find out. Marine grade plywood has become less than perfect. The best part of marine grade plywood was the absence of voids. I have seen this not be the case anymore. When cutting it I have seen voids when really there should be 0.

 

[cribber]

Re: Confused about plywood.

Here is what wikipedia defines as marine grade plywood.
http://en.wikipedia.org/wiki/Plywood#Marine_plywood
The prices they quoted may be a little on the low side but the description is sound.

 

[joewithaboat]

Re: Confused about plywood.

Here is what wikipedia defines as marine grade plywood.
http://en.wikipedia.org/wiki/Plywood#Marine_plywood
The prices they quoted may be a little on the low side but the description is sound.

Id say wikipedia is way off on this one. Ive used 3 different species of marine plywood non of which were "tropical" species. The popular species here lately is Douglas fir. I am not a boat builder or in the boat industry but i own a custom millwork shop and occasionally we get a job that calls for marine grade. It also cost a little more than standard plywood but is no where near the $100.00 stated by wiki. Its around $55.00 in the whole sale market.

http://www.plywoodcompany.com/application/home/itemdetails.aspx?categoryid=147&itemid=322

 

[joewithaboat]

Re: Confused about plywood.

To add to this. Plywood use to be interior or exterior. In recent years they have started making all plywood with exterior grade glues. So in reality any good grade plywood will suffice for flooring. If you want to use a non marine grade look at cabinet grade plywood and by all means ask about the glue used. A supplier of same will know or find out. Marine grade plywood has become less than perfect. The best part of marine grade plywood was the absence of voids. I have seen this not be the case anymore. When cutting it I have seen voids when really there should be 0.

All manufacturers use different methods to make plywood and standards are continually changing. We cut up hundreds sometimes thousands of sheets of ply goods in a year so i see quite a bit of it. Interior plywood is not made with exterior glue that Ive ever heard of. If interior plywood gets wet it will come apart. Currently the maple and birch sheet good we use are glued up with a soy based glue.
The most resent job we did with marine ply was with 1/2 and 5/8 A/B Doug fir marine and was void free and a joy to machine. It was around $50.00-$60.00 per sheet. Ill post some pictures in a bit.

These are seat bases for a 60's Grayhound bus restoration. There are 43 seats, we have to refurb the backs next. The seat frames are light weight tubular steel and were made by an aircraft seat maker at the time. The original contoured foam on the seats were poured in molds. Unfortunately it is a volunteer, non profit type thing. It is going to a museum upon completion.

 

[fishrdan]

Re: Confused about plywood.

Since this is in the pontoon forum I'm guessing the OP is asking about pontoon decking, and yes, that is treated. though there are many types of "marine" plywood

Marine grade plywood has become less than perfect. The best part of marine grade plywood was the absence of voids. I have seen this not be the case anymore. When cutting it I have seen voids when really there should be 0.

I agree, I bought several sheets of doug fir marine plywood for my rebuild and it certainly wasn't void free. I was seeing red while screwing down my newly vinyled deck panels and busted through 2-3 times... I also saw several voids per sheet while cutting it up.

BTW, doug fir marine plywood also has the plies laid at 45*, instead of 90* like normal plywood. That's one of the big factors in making it stable and retaining it's flatness

 

[5150abf]

Re: Confused about plywood.

I see your point, marine is "treated" but it isn't treated like you buy at home depot, they aare different but the marine ply still has been treated with chemicals to keep growth and decay in check.

 

[joewithaboat]

Re: Confused about plywood.

I see your point, marine is "treated" but it isn't treated like you buy at home depot, they aare different but the marine ply still has been treated with chemicals to keep growth and decay in check.

Please see link above

Fisherdan is spot on!

Third paragraph, from marine plywood manufacturer... "Marine-grade plywood is not treated with any chemicals to enhance its resistance to decay. If decay is a concern, it should be pressure-preservative treated to an appropriate standard."

If using for pontoon decking (which i know almost nothing about) I think you would want this which appears to be "marine" plywood that has been "pressure treated" then "kiln dried" by a second party after manufacturing, like suggested by plywood manufacturer in above link.

https://www.boatcarpetcentral.com/marine-boat-plywood <---<---this for deck/pontoon boats

I have used the pressure treated plywood from my local Home depot a few times. It was b/c ext and not kiln dried after treating. So it is very wet and will curl up badly as it air dries. That along with its surface defects i would think would make it a poor candidate for pontoon decking.

If you used marine plywood that had not been treated, i would think it would go down nicely (flat and smooth) but would fail prematurely under carpet because it would stay wet too often and suffer from rot and decay.
To the O/P, Hope this is helpful!

 

[jeeperman]

Re: Confused about plywood.

Wood that has been pressure treated with the old formula is now also refered to as "marine" grade or use or type.
It is also the type recommended for below or on grade use.
So "marine plywood" is now also a term used for regular exterior grade wood plywood that has been treated with the old type preservative.

The consumer type treated lumber found in the big box stores is almost always the new type of treated lumber.

So when talking about "marine plywood" you have to be specific because there are so many variations of what is called "marine plywood"

 

[joewithaboat]

Re: Confused about plywood.

Wood that has been pressure treated with the old formula is now also refered to as "marine" grade or use or type.
It is also the type recommended for below or on grade use.
So "marine plywood" is now also a term used for regular exterior grade wood plywood that has been treated with the old type preservative.

The consumer type treated lumber found in the big box stores is almost always the new type of treated lumber.

So when talking about "marine plywood" you have to be specific because there are so many variations of what is called "marine plywood"

Information given like this only adds to the confusion... please provide info of your above statement....

This is the information i am going by
http://www.apawood.org/level_b.cfm?content=srv_help_prd_marine

As far as i am aware any "pressure treating" of "Marine" plywood is done by a second party other than the original manufacturer. Because of newer EPA regulations there are different levels of pressure treating. Most but not all are still green in color.

Also as far as i am aware in the wood industry "marine" plywood goes by APA grading and is not pressure treated.

I'm not trying to argue with you guys just trying to make it easy for folks to find what they need. If you call a plywood distributor looking for "marine" plywood it will not be "pressure treated". If you go to Home Depot and buy "pressure treated" it will not be "Marine Grade"

As provided in post #11 there are companies that provide "Marine" grade that has been "pressure treated"

"Marine" is a grading term "Pressure treated" is an additional process added to a many grades of lumber and plywood.

I hope i am being helpful

 

[jeeperman]

Re: Confused about plywood.

Information given like this only adds to the confusion... please provide info of your above statement....

This is the information i am going by
http://www.apawood.org/level_b.cfm?content=srv_help_prd_marine

As far as i am aware any "pressure treating" of "Marine" plywood is done by a second party other than the original manufacturer. Because of newer EPA regulations there are different levels of pressure treating. Most but not all are still green in color.

Also as far as i am aware in the wood industry "marine" plywood goes by APA grading and is not pressure treated.

I'm not trying to argue with you guys just trying to make it easy for folks to find what they need. If you call a plywood distributor looking for "marine" plywood it will not be "pressure treated". If you go to Home Depot and buy "pressure treated" it will not be "Marine Grade"

And if you visit a real lumber yard that deals a lot in treated lumber used in saltwater, such as docks and boatlifts, etc. and then ask them for marine grade plywood, you are going to get CCA treated (the old stuff) plywood.
Not many consumers are going to be buying any type of plywood from a plywood distributor.
And thus the advent of CCA treated plywood also being called "marine grade plywood" is very likely.

As provided in post #11 there are companies that provide "Marine" grade that has been "pressure treated"

"Marine" is a grading term "Pressure treated" is an additional process added to a many grades of lumber and plywood.

I hope i am being helpful

CCA treated is the old formula I refered to.

Here ya go, from the EPA...............http://www.epa.gov/oppad001/reregistration/cca/awpa_table.htm

Try CCA-C9 or CCA-C18 or CCA-C22

"Marine construction: Wood used for piling (sheet, round and square), Timbers, Walers, and Plywood and Framing, Stringers and Cross Bracing; wood for marine construction for salt water use (also includes brackish water) (immersion and/or subject to saltwater (or brackish water) splash ["subject to saltwater (or brackish water) splash" means any member of a marine structure which is positioned above mean high tide, but is subject to frequent wetting from wave action]), [Pilings (sheet, round and square), Timbers, and Plywood; Walers, Framing, Stringers and Cross Bracing (2"x8" and/or 3"x6" and larger dimensions and treated to a minimum of 0.60 pcf)"

My first post to this thread was to point out that CCA treated plywood is getting to be called "marine grade plywood" by lumber yards that sell marine grade (CCA) treated lumber.
So when asking for marine grade, the buyer must be specific in what he wants.

 

[joewithaboat]

Re: Confused about plywood.

CCA treated is the old formula I refered to.

Here ya go, from the EPA...............http://www.epa.gov/oppad001/reregistration/cca/awpa_table.htm

Try CCA-C9 or CCA-C18 or CCA-C22

"Marine construction: Wood used for piling (sheet, round and square), Timbers, Walers, and Plywood and Framing, Stringers and Cross Bracing; wood for marine construction for salt water use (also includes brackish water) (immersion and/or subject to saltwater (or brackish water) splash ["subject to saltwater (or brackish water) splash" means any member of a marine structure which is positioned above mean high tide, but is subject to frequent wetting from wave action]), [Pilings (sheet, round and square), Timbers, and Plywood; Walers, Framing, Stringers and Cross Bracing (2"x8" and/or 3"x6" and larger dimensions and treated to a minimum of 0.60 pcf)"

My first post to this thread was to point out that CCA treated plywood is getting to be called "marine grade plywood" by lumber yards that sell marine grade (CCA) treated lumber.
So when asking for marine grade, the buyer must be specific in what he wants.

I'm aware of different grading of CCA and fasteners you can and can not use with them...
And...
That's all fine well and good, but just because your local lumber supplier uses improper terminology doesn't mean you can change lumber grading rules. Just because they carry "pressure treated marine plywood" doesn't mean "marine" grade plywood everywhere is "pressure treated" and ever ones "pressure treated" is "marine grade" I would bet that the vast majority of marine plywood sold is not ever pressure treated. Additionally the vast majority of treated plywood is not marine.

"Marine" and "Pressure treated" are 2 different things. You can have both but most times one is without the other.

 

[fishrdan]

Re: Confused about plywood.

I always love plywood threads, they are almost as good as "which oil" threads

 

[joewithaboat]

Re: Confused about plywood.

I always love plywood threads, they are almost as good as "which oil" threads

I was not aware of this... but now i know:facepalm:

Oh and for the record... Mobil 1 extended performance

 

[5150abf]

Re: Confused about plywood.

Yup you are right marine plywood is untreated, it is just one of those unexplained miracles how it can take constant submersion for years and years without failing and it is just normal untreated plywood, amazing stuff.

 

[joewithaboat]

Re: Confused about plywood.

Yup you are right marine plywood is untreated, it is just one of those unexplained miracles how it can take constant submersion for years and years without failing and it is just normal untreated plywood, amazing stuff.

Do you have trouble reading? I even provided links to APA and manufacture guidelines :facepalm: So because your lumber yard has treated #1 yellow pine dimensional lumber does that mean all #1 yellow pine dimensional lumber is now treated?? heck no. The Grade of "Marine" has absolutely nothing to do with it being pressure treated!

Lets make this simple......
To the O/P. You can by "marine grade" Plywood that has been treated. The APA "marine" manufacturing guidelines have nothing to do with it being treated and in fact state very clearly that it is NOT TREATED.
If you find Pressure treated marine plywood it has been treated by a second party and has nothing to do with the grading of "marine"
It would simply be marine plywood that has been pressure treated!

 

[cribber]

Re: Confused about plywood.

I guess the term "marine grade" can be interpreted in so many ways like "tastes great less filling!" Lots of good info in this thread!!