# Marine Grade Plywood Lifespan



## jonsey (Sep 19, 2011)

I was working with a client making some recommendations for a bathroom remodel. One suggestion that I made was to use 3/4" Marine grade ply to back the walls so that installation of grab bars or any other item wouldn't be restricted to a certain location, based on spot blocking or "hitting the studs." 
The contractor who was working onsite jumped right in and said that was a bad idea- He said that the plywood eventually absorbs moisture, separates and ruins the walls. 

Most of the places that help spec bathrooms suggest this building method- I haven't seen this mentioned as an issue before- but I guess I haven't asked what the lifespan of marine grade ply actually is either. What do you guys know about this?


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## MALCO.New.York (Feb 27, 2008)

Marine Grade Plywood NEEDS to be coated in order for it to be properly effective.


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## B.D.R. (May 22, 2007)

I would not do it.There are better ways


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## Big Shoe (Jun 16, 2008)

No need for marine grade.......waaaaaaaaaaaaaaaay overkill. :no: 

Reg plywood would will be just fine. 


If water ever got that far...You'll have more things to worry about than that.



Whats that stuff cost'n now, 75.00 a sheet? (edit)


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## bluebird5 (Dec 13, 2010)

why not put som blocking between the studs where the bars will be?


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## parkers5150 (Dec 5, 2008)

what's wrong with 1x??


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## Big Shoe (Jun 16, 2008)

I've seen specs calling for min 2x material for backing or 3/4 plywood.

1x material can split. I've installed alot of grab bar backing in my days. I would prefer 3/4 plwood first,2x second and 1x third.


let me add 1x is pretty strong and most used stock for backing.


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## Jaws (Dec 20, 2010)

We use 3/4 ply or blocks for grab bar backing, Densesheild over that. Has worked great for a long time as long as it is installed properly. If water gets behind the Densesheild there is a big problem no matter what the plywood. Not to mention, why use the marine plywood when the rest of studs are untreated?


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## Hardly Working (Apr 7, 2005)

I agree Marine Ply is great if it's coated. My 1991 outboard tunnel boat is holding up just fine, but it's also coated in West Systems.

I normally dap my studs and run strips of 3/4 CDX nailed with 8d ring shanks or galv.


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## Jaws (Dec 20, 2010)

Hardly Working said:


> I agree Marine Ply is great if it's coated. My 1991 outboard tunnel boat is holding up just fine, but it's also coated in West Systems.
> 
> I normally dap my studs and run strips of 3/4 CDX nailed with 8d ring shanks or galv.



Dap?


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## Hardly Working (Apr 7, 2005)

Dado for you Texans

Hey jawtrs is Highland Lakes anywhere the same a Highlands TX? Use to race in Highlands a few years back


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## Rob1954 (Jun 22, 2010)

I was always told that "marine grade" refered to the type of glue used and the allowable amounts of voids in the veneers. It has more strength than other grades, but offers nothing for resistance to decay due to moisture.


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## CO762 (Feb 22, 2010)

jonsey said:


> I was working with a client making some recommendations for a bathroom remodel....
> The contractor who was working onsite...


Where do you fit into the food chain?


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## Jaws (Dec 20, 2010)

Hardly Working said:


> Dado for you Texans
> 
> Hey jawtrs is Highland Lakes anywhere the same a Highlands TX? Use to race in Highlands a few years back


Highland Lakes is a region not city. 5 major lakes 40 miles west of austin, in the hill country. Horseshoe Bay, Marble Falls, Kingsland. Most of our work is in Horshoe Bay. 

Not sure where Highlands is. Its a big ass state. I just drove 350 miles one way to the Mexican border to hunt dove


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## The Coastal Craftsman (Jun 29, 2009)

Anyone else tried them 300lb drywall screws? I was a little concerned that they wouldn't work but they work well. They are also 300lb in all directions. 2 of them mounted to CBU a grab handle should be more than enough. I tested one in some 1/2" drywall in my basement and mounted one to the wall and stood on it. They held up and so did the drywall. I bet they hold even more in thicker drywall and tougher backer board.


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