Help required - Plywood in the US

Jul 31 '12 13 Last Comment
Jul 31, 12 6:25 pm


I would love some assistance on plywood in the States. I am working on a project that requires the use of plywood and I have a few questions - chiefly due to a translation of NZ/Australian standards into US standards:

1. What is the availability of metric sized plywood in the US? I have assumed that your 8x4ft is obviously widely available, but do you also have access to the metric version which is slightly smaller (2400mm x 1200mm as opposed to 2440 x 1220mm (imperial)).

2. In NZ and Australia, we typically treat the timber with copper or spirits for external use - this is aside from the glue. I see from the APA that there are a variety of exposure classes but this has more to do with the number of veneers and glue - is chemical treatment common or even in use?

3. Structural grade ply - is there a separate class of ply that is structural grade - i.e. used for bracing, structure etc, or is there simply a metric between number of veneers and structural grade.

Any help much appreciated!



Jul 31, 12 6:38 pm

1. it's all imperial, but they'll cut it for you to any size, so getting hard metric would not be hard. 

2. All exterior plywood is typically pressure treated. It makes the plywood heavier but more moisture resistant. By code, plywood used as sheathing may have to be fire treated. You can't have both treatments applied at the same time.

3. There are many grades of plywood. For sheathing typical grades are (Exterior, Structural I), (Exterior), (Exposure 1, Structural I), (Exposure 1).

I assume you are preparing for your NYC visit... If you are buying building supplies here, stay away from big box stores like Lowes or Home Depot. They are just horribly unreliable when it comes to delivery. There are many independent lumber yards that can deliver on same day as order.

Jul 31, 12 6:46 pm

1.  we have saws, and plywood can easily be cut.  i doubt you can find metric sizes from a US manufacturer/distributor of plywood.

2.  i think copper is common now here for treating exterior grade wood.  i wouldn't trust plywood too much if it's directly exposed to weather because the layers can still warp a bit and i just don't think glue works that way.  that's an opinion and i expect the plywood/glue lobby would disagree with me.

3.  i haven't heard of structural grade plywood.  that should just be by width, and number of veneers should really only vary by width too so if a certain thickness is 5 layers, that thickness is probably going to always be 5 layers.  you might be able to get different species of wood, like hard wood or softwood, but I doubt that makes too much difference.

edited to say that rusty says there is structural grade plywood.

Jul 31, 12 6:48 pm


Thanks Rusty. Yes, This is for the project. We are using CNC so we have everything machined and then delivered. We want to use standard sheets to minimise work and cutting time. So the cut paths I currently have are for metric sizes, so I will do an imperial version.

In NZ we treat ply with copper or other chemicals to prevent rot and delamination - probably because we use Pinus Radiata. 

When you say Exposure 1 Structural 1, is this a ply that is both for exterior use and is also structural?

Is imperial the right term to use?

Jul 31, 12 6:53 pm

Thanks Curt,

I am working with a supplier that brings in a 3/4 inch 13 veneer ply which should be as rigid as x$!@ but you do pay for it.

Who is a good manufacturer/supplier of ply to use? That has national coverage.

And is 5/8 more common than 3/4 as a thickness?


el jeffe
Jul 31, 12 7:10 pm


5/8 is commonly used on walls & roofs, 3/4 mostly for floors. both are readily available.

wood products are pretty regional, but georgia-pacific, boise-cascade and L-P (louisiana-pacific) are big players w/r/t wood products that are national.

Jul 31, 12 7:19 pm

more plys can't be good, can it?

Aug 1, 12 5:35 pm

If you really need weather-resistant plywood, look at Marine Grade. It's a lot more expensive ($80 a sheet or more), but it's made of sterner stuff than the lesser grades.

Aug 1, 12 6:05 pm

dia, here is a blurb on plywood grades from my notes:

Durability (Weather Resistance): Plywood is classified under DOC PS 1 as Marine, Exterior, Exposure 1 (Interior bonded with exterior glue), Exposure 2 (Interior bonded with intermediate glue), or Interior. Marine plywood requires B grade or better veneers of either northern Douglas fir or western larch (for the core and both faces) and exterior glue. Exterior plywood requires C grade or better veneers (core and faces) and exterior glue. Exposure 1 plywood allows D grade veneers, the same as Interior plywood, but requires exterior glue. Plywood manufactured to comply with DOC PS 2 is classified as Exterior, Exposure 1, Exposure 2, or Interior based on performance testing without grading the veneers that make up the plywood. The glue bond test for Exterior and Exposure 1 grades under DOC PS 2 are the same as those under DOC PS 1. For OSB, there is no Exterior classification, and qualification for Exposure 1 is based on testing for bond failure after soaking in 150 deg F (66 deg C) water followed by drying at 180 deg F (82 deg C). Although Exposure 2 is referenced in both standards, no products are currently produced with this classification.

yeeeaaaaaahhhhhh plywood!

Aug 1, 12 7:01 pm

Thanks Rusty,

For my purposes, Exterior and Exposure 1 is the way to go. Yay plywood indeed!

Aug 1, 12 11:54 pm

"Formaldehyde!  I love the smell of formaldehyde in the morning!  It smells like... victory.

Someday this project is gonna end..."

Aug 18, 12 6:54 pm

Just out of interest, why do you need to import plywood from Australia to the US?

Aug 19, 12 6:39 pm

I don't need to import p[plywood, I need to translate a design based on metric sizing to imperial sizing and specify the material correctly.

ps. its NZ

Aug 21, 12 6:31 pm ls like being from South Dakota and people think your From North Dakota.

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