Pressure Treated Plywood?

[Craig Mitchell]

I'm not sure if this is the right forum but I'll throw it out here. I am working on a backyard fence design using pressure treated plywood and was wondering if anyone here as ever worked with it before. It will be a post and panel design.


Are there any warping issues for exterior use I need to be aware of? It will be painted.


I was told by the guy at the lumber yard the PT Plywood would be better to use than MDO plywood in a fence design.


Any suggestions, thoughts, etc would be welcome!

[Chuck Saunders]

It will warp if not restrained by the panel framing. The plywood is probably finished C-D if it is like what I have. Does not need paint as I think the MDO would but not near the quality of MDO.

[Craig Mitchell]

It will warp if not restrained by the panel framing. The plywood is probably finished C-D if it is like what I have. Does not need paint as I think the MDO would but not near the quality of MDO.


Thanks! Yes, it would be framed in.... sort of like a Japanese panel wall. The plywood would be painted and roughness would be okay. I'll have to go look at them in person and see what the quality is.


Imagine a post and panel design with framing around each panel and center supports. Something to that effect.


I'm concerned about how the panels would hold up in weather. Veener splitting, warping, etc.

[Von Bickley]

Craig,

My experience with pressure treated plywood is that it will warp up real bad & real fast....:D

[Greg Cole]

Hi Craig,
I gave some feedback to your post in the design forum. Seems to be the across the board answer about warpage....

Cheers.
Greg

[Tom Hargrove]

It warps more than any material I have every used. The only time it does not appear to warp is when it is used for sheathing - glued and screwed.

I have tried it for several outdoor projects, and I will never work with this material again for a three dimensional project.

[Larry Anderson]

Do you think it would be OK for a shed deck floor? Deck would be probably 8-10" above ground level.

[David Romano]

I've used it, unfinished, and it warps terribly. I would not expect a finish to to make any difference. MDO wouldn't be weatherproof at all, I don't understand that recommendation. All it is is plywood with an MDF skin.

The surface is not as nice, but Advantech would work for you, and it's cheap too. You could experiment with veneering it using thin strips of your preferred wood, adhered with a weatherproof sealant. Some of the glues used to hold flooring down would probably do the job, and the serrated trowels will control the thickness of the application.

David

[Robert Meyer]

Larry
I have used 3/4" Pressure treated ply on a shed floor with good results. It is on joists about 6" above grade. I glued and screwed it down and it hasn't moved for 6 years. Latest issue of Fine Homebuilder has an article on building sheds but I haven't had a chance to read it yet.

[Larry Anderson]

Robert
Actually I'm going to build a roll-off roof observatory. Now that I think about it, if the siding extends below the floor any ply should be acceptable. Unless of course the PT is cheaper.

[Joe Spear]

The pressure treated plywood I've seen at the borgs is god-awful, rough, damp, splintery stuff.

[Gary Redden]

MDO wouldn't be weatherproof at all, I don't understand that recommendation. All it is is plywood with an MDF skin.


That is not a true statement. MDO stands for medium density overlay which comprises of a low pressure laminate applied over exterior plywood. "MDO Plywood is produced with a resin-treated fiber overlay which is generally smooth and opaque. This allows for rapid, even paint and coating applications. MDO plywood is manufactured with 100% waterproof adhesives and has an inner ply construction of C grade veneers and B grade or better face and back veneers"

Gary

[Greg Hines, MD]

I have used pressure treated plywood for roof sheathing on my firewood shed, and since it is screwed to the underlying framework, it has stayed flat. Then again, it is shingled so that it does not get damp either.

Doc

[Stephen Edwards]

Do you think it would be OK for a shed deck floor? Deck would be probably 8-10" above ground level.

It will work fine for shed floor, if that's what you mean. But out in the weather....I wouldn't use it. I have it in my shop....12x 48 section of an old barn. Been down for 5 years now, no problems. I screwed it down very well.

[David G Baker]

I have a trough made from 3/4 inch pressure treated plywood that I feed wild deer in, it has been out in the weather for the past 5 months and shows no sign of warping.

[David Romano]

Thanks for the clarification on that.

David


That is not a true statement. MDO stands for medium density overlay which comprises of a low pressure laminate applied over exterior plywood. "MDO Plywood is produced with a resin-treated fiber overlay which is generally smooth and opaque. This allows for rapid, even paint and coating applications. MDO plywood is manufactured with 100% waterproof adhesives and has an inner ply construction of C grade veneers and B grade or better face and back veneers"

Gary