Plywood grades

[Kevin A]

Coop, Siobhan is an Irish step dancer we know..... She is from Listowel, County Kerry, Ireland... Shirl and I love Ireland and try to visit often. I won't tell Shirley what you said.. She might not like the implication./g/

About plywood, I think I've got enough information..... I really don't want to use 3/4, but for safety sake, I don't want to under build with 1/2 and have problems down the road (so to speak).... I can look at 5/8, but the weight/$$ savings is hardly worth it....

Arne,
Where was this photo taken? Interesting to see the Stars & Stripes flying along side the Orange & the Green, and somewhere between Killarney & Limerick.
Oh, and to avoid being accused of contributing to a thread hijack, Have you priced plywood on any of your trips to Eire?

[goldcoop]

Coop, what was the widest unsupported span you had?

Arne-

If you remember our sofa/bed arrangement, we used 1/2" for that...

23" x 72" for each of the sections, basically unsupported except along the long edges.

It flexes alittle when the three of us are in there moving around, but thats about it.

IMO, the 5/8" @ 24" is a good compromise.

Cheers,

Coop

[Arne]

The photo was taken in Listowel center. Just south of the Tarbert ferry which crosses the Shannon Estuary..... a beautiful area. Scroll down till you see the car image on the left side. That is near Foynes, where the 'flying boats' from New York used to land, decades ago... I have to go check flights, might be time for another "Ireland fix"....

http://www.shannonferries.com/route/

http://www.flyingboatmuseum.com/

[Arne]

An update, using a superficial test method.... based on a question above, I took a 2 sq. ft. piece of birch ply and supported all 4 sides with scrap 2x4's. It was quite stiff compared to my original 2 (opposite) side test. This got me thinking, that it also depends on which way the grain runs.

My conclusion (for my needs) is that I can probably get away with 1/2" plywood (birch, a better quality) if I run the grain front to back. This puts a joint going the same way, the long way, but I can deal with that. I have to have joints somewhere, so will lay the ply the way it works best.

[Guy]

Dear Arne,

Really good test and decision. It is exactly what I am doing on teardrops4vets. The sides are 1/2 Baltic birch with the woody frame also being Baltic birch, and at the joint there is 4" strip of 1/2" Baltic birch sandwiching from the inside. So that give me 1 1/2" thick x 2" wide sandwich frame the no span being more than 36".

[Artificer]

Coop, what was the widest unsupported span you had?

I think I could do 24" with 5/8, but think with 1/2 it would have to be less than 24". That means a lot of supports underneath, and I'd like to do 24" from front to back with nothing across the 5' width... I just don't think 1/2 would handle it, though 5/8 might with a stringer down the middle....

If I have to add a lot of support underneath, it adds complexity to the build, weight and a bit of $$.....

My floor is 15/32" BC with 2x2x1/8" 24 on center steel supports. With just the plywood on it, the floor was springy. I didn't mind because of a couple of factors. The plywood had a span rating of 16"/32" (floor/roof) I'm not putting furniture in it, so I went with the roof span. I'll never be standing up on one foot in the trailer, once its ceiling is on. Once the futon is in, I'll never notice it because of the cushy softness. I'll have at least 2 points of support, or my big butt to spread the load.

Once I filled the spaces between the 2x2 supports, and added the fiberglass to the bottom, the deck became much more solid. I wanted the insulation of the foam, so the weight wasn't a consideration. If you're going for light weight, it might be an idea to use. Last weekend I made up a panel of 2"extruded foam and 1/8" skins. Its 48" long, and 4" wide. It will support my weight (over 200lbs) when supported only on the ends.

[cracker39]

Plywood grades are (in best to worst) - A, B, C,D for face (front) grades & 1, 2, 3, 4 for back grades. The lower the letter or number the better the material will be. All of our plywood is graded to the standards of the Hardwood Plywood & Veneer Association

I don't know if I have ever seen grades marked with a number...maybe I just haven't been that observant. I see AC, BC, CDX, etc. in the box stores. I used 3/4" BC for my floor and frames for my fenders. The B side is smooth enough to apply vinyl flooring.

[Artificer]

Plywood grades are (in best to worst) - A, B, C,D for face (front) grades & 1, 2, 3, 4 for back grades. The lower the letter or number the better the material will be. All of our plywood is graded to the standards of the Hardwood Plywood & Veneer Association

I don't know if I have ever seen grades marked with a number...maybe I just haven't been that observant. I see AC, BC, CDX, etc. in the box stores. I used 3/4" BC for my floor and frames for my fenders. The B side is smooth enough to apply vinyl flooring.

Letter/Number is for hardwood plywood. Softwood plywood uses Letter/Letter. Big box stores aren't known for the quality of their plywood, so if you haven't seen it on the hardwood plywood, it might be "furniture grade" or something similar. Not a standard specification.