Exterior Vs Interior Plywood - Need Advice

[teardropty]

I am new to the TD building world. I have been told that interior grade plywood simply CANNOT be used to construct the walls of my TD. Is this an accurate statement?

I am looking to use 3/4" Birch Cabinet Grade Plywood. It is considered interior grade. I am looking to go cheap (yes, I know all the arguments about you get what you pay for) and use Marine Spar finish over the interior plywood.

My belief is that if I coat all sides and therefore seal the plywood with marine spar it will give me usable results. Please provide any comments, suggestions and opinions. Thanks.

[Steve_Cox]

I am new to the TD building world. I have been told that interior grade plywood simply CANNOT be used to construct the walls of my TD. Is this an accurate statement?

I am looking to use 3/4" Birch Cabinet Grade Plywood. It is considered interior grade. I am looking to go cheap (yes, I know all the arguments about you get what you pay for) and use Marine Spar finish over the interior plywood.

My belief is that if I coat all sides and therefore seal the plywood with marine spar it will give me usable results. Please provide any comments, suggestions and opinions. Thanks.

TearD,
Welcome to the forum....

CANNOT??? who the hell said that? You can do anything you want. I used ply for my walls that wasn't exterior, it is now encapsulated with epoxy on the end grain and back, the red oak side is coated with marine spar polyurethane. The plywood you chose is a good choice. It is up to you to protect it from water intrusion.

[48Rob]

The reason interior grade plywood can't be used for exterior projects is because it isn't designed for it.

The glue can't stand up to the moisture that it would be exposed to outdoors, and it would quickly delaminate.

That said, Steve is 100% correct.
Interior, or exterior, it is up to YOU to protect it from water intrusion...

You can make a trailer out of paper, and it will be fine outside as long as you have made sure moisture won't get in.

Most people do not understand that to properly seal wood, you have to do more that throw a quick coat of varnish or paint on the part you see.

All sides that may be exposed must be sealed, and sealed well, this includes edges.

It is good practice to evenly coat ALL sides so that the moisture barrier is equal and even from front to back.

And it is a rare piece that will survive long with just one or two coats of anything.

Encapsulate is the key phrase for success.

Rob
Who used 3/4" interior Birch...

<img src="http://img.photobucket.com/albums/v284/1948rob/Cabin%20car%20project/bridge.jpg?t=1209037483">

[teardropty]

I appreciate your comments and I agree its about encapsulation. Just nice to hear some common sense support. Thanks.

Ty
who used 3/4" interior birch and is praying his sealing methods reach ALL parts of the wood.

[mikeschn]

I used baltic birch on the Escape Hatch, and covered it with Porch and Floor paint, which is oil based. It wasn't enough. I have a little bit of delamination in a couple spots.

The generic ET is being built out of cabinet grade birch plywood, interior grade. I plan on putting on a layer of CPES and then rolling on a layer or two of white Uniflex 255 from the RotDoctor. That's the stuff they put on boats. That should keep the interior grade plywood under control, ya think?

Mike..

P.S. The finish will end up like the one on the Baja Benroy, which you can see here...
http://www.mikenchell.com/Baja_Benroy_P ... ndex7.html

[madjack]

...we use a cabinet grade of ply for building...unless the product you use SPECIFICALLY states it is for indoor use only, it is probably made with a water resistant glue...total and through encapsulation is the key to longevity...afterall, many of the olde tears used masonite for a substrate...
madjack