Plywood ??

[dstryr]

Hey, all,
Have a question for the guys who know their stuff about plywood grades and application.

I have a project that requires a semi trailer on a jobsite and we had built a 16'x40' scaffold based dock, 2x10x16 or so microlam stringers on top of which they put 2 layers 4x8x3/4 (I think BC) grade plywood- 4 green stripes.

The idea is that as it shreds from pallet jack traffic we peel off the top layer and work from the next layer, or just re-sheet the top as needed.

In a short time, the rain and temp swings cause the ply to bubble and split and I not sure this was the right direction to go, though the builder assured me this is not totally uncommon.

Is there a grade that is 'commonly used' on a dock/deck application like this?

I am reading that green treated is more about bug and fungus control, not seeing anything about the glues that keep it together.

Please let me know your advice and or experiences.

Thanks,
Frank

 

[Arps]

We use marine grade where I work on anything that might get wet. Im not sure what the difference is though, but we dont have that issue.

 

[turbowoodworker]

Either treated or marine grade plywood would be better than CD but if it is out in the weather, no grade of plywood will last long. It will delaminates with time. I think for what you are trying to accomplish, and you plan on using it for an extended time, I would continue using the CD or even OSB in layers and and just replace it frequently. Count it as the cost of doing business. I just don't think you'll get much in extended life out of the much more expensive marine grade.

 

[sweetcretin]

Paint it. Seriously... If water gets into the plywood, it's going to delaminate even if you use plywood with a water resistant glue like marine plywood. As such, you need to keep the water out. For that you can use paint or one of the sealing gel stains. This seems like be a perfect use of the 5 gallon cans of barn paint.

You said jobsite, so I'm assuming this is a temporary / semi-permanent fixture. If it's permanent, use appropriate decking not plywood.

 

[Ross/Kzoo]

Have you considered truck bed liner rolled onto the surface and sides?

 

[Nowater]

Twenty years ago I put a cut off piece of PT 3/4" ply in front of my garden shed and figured I'd replace it when it goes bad. I will too, pretty soon.

 

[Boomer343]

Plywood won't take the loading from the pallet jack wheels and will delaminate very quickly. Your deck needs to be planked with dimensional lumber which could go right over the existing plywood if it doesn't raise it too much.

 

[Voi]

Since you live in Nebraska and have Menards my first thought was their MDO plywood. According to their website it's $64.99 for a 3/4" 4x8 sheet. That's up considerably from the last time I used it.

http://www.menards.com/main/buildin...3-4-x-4-x-8-mdo-plywood/p-1358810-c-13339.htm

MDO is what highway signs used to be made out of, although I think the MDO that Menards carries is a step below that quality. I used a painted piece as a platform for a camping grill for several years. Never came inside and help up great in a horizontal application.

The outermost veneer is resin impregnated paper and I'm just not sure how well it would hold up to pallet jack traffic. The wheels would roll great but that same smoothness might make it slick for foot traffic.

It's a great surface for paint, however, so if you can find something like a roll on bed liner that has the right tradeoff between grip for foot traffic and slickness for pallet jacks rolling, I think it would work great.

But at that price I'd price other options as well.

 

[dstryr]

Thanks for the replies. I think I'll be doing one of two things, based on how the plywood holds up. Either re-sheeting it with another layer of ply or dimensional lumber once the top layer gives up. Its been sheeted for 4 weeks now but we haven't really gotten into beating on it yet. The next several weeks should be telling.
Appreciate the advice!
Frank