new deck

[pontoon61]

I am replacing my deck for the 1st time. Can anyone tell me if I have to put anything on the marine plywood before putting it down? Do I need to seal the holes that are drilled for the fasteners, and what kind of fasteners are best?
Thanks for any help.

 

[ezmobee]

Re: new deck

Yes. Marine plywood isn't treated against rot so you'll need to seal it. What you do that with is your choice and depends on how long you want it to last. From best to least bestest....
- Fiberglass it (poly or epoxy resin)
- Coat with epoxy resin (poly is no good by itself)
- Marine spar varnish
- Quality porch and floor paint

Really coat the edges well with whatever you choose.

 

[nikogto]

Re: new deck

Marine Plywood, of good quality is pressure treated, if not it would not last more than 2 years without falling apart. Always use stainless steel hardware, it will resist corrosion and will come off easily if you need to remove it later on. I re-built an 86 model toon a few years back and was able to save most of the stainless hardware for the re-build. You can find complete decking kits on pontoonstuff.com And you should be able to find good marine plywood at a commercial luber supply yard. You won't find it at Lowe's or Home Depot. Good luck.

 

[ezmobee]

Re: new deck

Marine Plywood, of good quality is pressure treated

I suppose the "of good quality" makes your statement debatable. Not all marine plywood is treated. In doing some research to try to prove you wrong I found this http://www.pontoonstuff.com/pontoon-boat/144-marine-plywood.asp which appears to be marine, and treated, and should be IDEAL for your 'toon deck.

 

[EGlideRider]

Re: new deck

And if you do seal it, do not seal the bottom. Water will find a way into any sealed wood and it needs an exit to prevent rotting.

 

[nikogto]

Re: new deck

I suppose the "of good quality" makes your statement debatable. Not all marine plywood is treated. In doing some research to try to prove you wrong I found this http://www.pontoonstuff.com/pontoon-boat/144-marine-plywood.asp which appears to be marine, and treated, and should be IDEAL for your 'toon deck.

If it is "marine plywood" then it is treated wood. Otherwise it would just be plain old plywood. "marine" meaing that it is suitable for marine applications, and harsh water conditions. You'll also see if you compare the 2 woods sheets, marine plywood is alot smoother surface and multiple layers comparred to your typical home improvement lumber. I remember looking into this when I was getting ready to re-build my boat a few years back.

 

[jeeperman]

Re: new deck

I think some semantics are in play here.

Before treated wood came onto the scene, there was "marine plywood".

Which was basically 7-plys of various hardwoods held together with waterproof/resistant glue. There are many varieties still available today, none of which are pressure treated with chemicals to resist rot or insects.

Then along came the advent of treated lumber and plywood.
Then CCA treated woods were outlawed for residential use.

Nowadays CCA treated wood is considered "marine grade" use treated wood.

And so CCA treated plywood has also come to be called "marine plywood".

http://www.marine-plywood.us/

 

[ezmobee]

Re: new deck

If it is "marine plywood" then it is treated wood. Otherwise it would just be plain old plywood.

Sorry this is just not correct. Marine is indeed a superior product to exterior but it is not necessarily treated.

 

[Woodonglass]

Re: new deck

I have to agree with EZ!!

I think the following facts will help clarify some things.

1. The glue
The glue for marine plywood should be the best permanent WBP(phenolic) glue . But there are more types of WBP glue for general exterior plywood .
2.
No defects (except sound pin knots) are allowed on the face/back of marine plywood . But some defects are allowed on the face/back of low grade (such as C/D grade) general exterior plywood .
3. The thickness of solid wood face/back veneer
For marine plywood : According to marine plywood standard BS 1088 , the thickness of face/back veneers for multi-ply construction should be 1.3 ~ 3.8 mm; for three-ply construction, the thickness should be about 0.5mm .
For general exterior plywood: The thickness of face/back veneers can be reasonably thinner for cost-saving .



4. The core veneer
For marine plywood : Usually, each core layer of long grain should consist of only one piece of core veneer . Edge joints are allowed . End joints are prohibited .
For general exterior plywood: Each core layer can consist of several pieces of core veneers . Both end joints and edge joints are allowed .
5. The species of wood
For marine plywood : The species should be hardwood of high density .
For general exterior plywood: The species can be hardwood of high density, MLH (Mixed Light Hardwood) and so on .
6. The application
Marine plywood is intended for boat-building or other marine applications, aircraft construction . Marine plywood can also be used in construction. Marine plywood can be used for all the jobs which can be done by exterior plywood .
General exterior plywood is intended for indoor or outdoor application where resistance to weather/water is required .

And Finally, From the APA

A P A
The Engineered Wood Association​

MARINE GRADE PLYWOOD​

Marine-grade plywood is made entirely of Douglas-fir or Western Larch. The grade of all plies of veneer is B or better. B-grade veneer may have knots but no knotholes. A-grade veneer has no knots or knotholes. Both A and B grade may contain wood or synthetic patches. Panels are sanded on both faces or Medium Density Overlay (MDO) or High Density Overlay (HDO). The maximum core-gap size permitted is 1/8 inch. Its exposure durability rating is EXTERIOR and the glue used is a fully waterproof structural adhesive. It is considered a "premium" panel grade for use in situations where these characteristics are required. It is available in 4x8-foot sheets of 1/4, 3/8, 1/2, 5/8 and 3/4-inch thickness. Sheets up to 5x12-feet are also available. Available grades are A-A, A-B, B-B (face-back), MDO and HDO.
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.
The detailed description of veneer grades and Marine-grade plywood is contained in Voluntary Product Standard PS 1-95 Construction And Industrial Plywood.
Sample Specification For Marine Grade
APA 3/8" B-B Marine Grade 4x8 10 pieces
Other Exterior Plywood Grades
Plywood panels rated as EXTERIOR but not Marine, such as A-B, A-A or C-C EXTERIOR, may contain any other permissible species and contain C-grade veneer. Unless specially improved, C-grade veneer is permitted to contain knots and knotholes up to approximately 1-1/2 inches across, and the inner plies may have core gaps up to 1-inch wide.

Technical Services Division
​

APA - The Engineered Wood Association

7011 South 19th Street . P.O. Box 11700 . Tacoma, WA 98411-0700


​

In MY opinion one of the BEST products to use for decks and Transoms is MDO or HDO. It Uses the EXACT same Glue and plys as Marine ply, the ONLY difference is it uses a Paper facing. However this is compensated for by the saturated resin that is used for this facing. I think every boat builder would be well served to research these products and make their own decisions. It is cheaper than Marine grade, VERY stable and Great to work with.

Check out this link

http://www.pacificwoodlaminates.com/img/PDFs/PlywoodGuide.pdf

I'm just sayin...
​

 

[5150abf]

Re: new deck

If you have actual marine ply then no you don't need to do anything to it, the lid to my livewell is made from marine ply and 3 years in looks exactly like it did when I put it on.

I made a big bird feeder 5 years ago from it too and it is showing no signs of wear even with 5 nasty Indiana winters on it.

For fasteners elevator bolts ar best in stainless, cover your cross members with something before setting your wood, we use a thin foam tape, all you need to do is keep the wood off the aluminum.

Use nylocks if possible and keep the wood really tight, it is a structural member so you don't want any gaps between the sheets.

 

[badbird]

Re: new deck

I am restoring my 1999 Bennington now and if anything needs to go down before "marine plywood" then Bennington is not building boats correctly. So my answer is NO nothing is needed before you lay down the "MARINE PLYWOOD"

BTW I bought my plywood from www.pontoonspecialists.com and they were really great to deal with and very helpful

Just my .02
Ron