Any way to waterproof plywood?

[xray328]

Hey guys I'm building a rack for a solar heater. I've gone with pressure treated lumber but now it's time to cover the face with plywood. Problem is that pt plywood is $35 a sheet.

I plan on painting it black anyway. Will normal exterior paint work to waterproof it? Maybe I'm over engineering this but I just want to make sure it stands up to the rain/snow.

 

[woodyp]

If you want it done "right"..........bite the bullet and buy marine grade. Or how about some of that concrete type hardi board?

 

[Richard320]

Once upon a time I added some Thompsons Water seal to some oil-based porch and floor enamel to paint the inside of a walk-in refrigerator. It dried almost like Melamine, similar to any white particle board IKEA-type furniture. Three years later, the next guy to paint it had a heckuva time. He didn't know and tried latex paint. What a mess!

 

[duraleigh]

PT plywood (the grade you are talking about) is pretty darn water resistant and you have two things going to help it even more....

1. Putting it on the slope will really help the water drain off (paint the backside about 6" up from the bottom and all edges of the plywood)

2. Any paint adds some "seal" to the surface and will help not only in "waterproofing" but helping that water run off as well.

Edges sealed all around and painted, I'd bet on an easy 10 years out of it

 

[bumpy1]

How about tar paper and roof shingles ....

 

[xray328]

That'd work but it's more expensive than the pt plywood. A bundle of shingles is what, $30? It'd take three to cover the rack, plus tar paper plus plywood. Thanks though.

 

[woodyp]

How about just the tar paper then? Or black plastic sheeting?

 

[peterdaly]

+1 for black plastic sheet. Btw - the track looks great.

Sent from my Nexus 4 using Tapatalk

 

[JVTrain]

I'd do a minimum of black plastic sheet but keep in mind that the plastic will break down over time due to heat and exposure and fall apart, peel, etc. You could do plastic and a layer of tar paper...

I'd also paint the whole thing with a latex based paint as duraleigh said. You can pick up left over paint for free at local/regional household hazardous waste facilities.

 

[Bama Rambler]

Given the installation I'd use CDX plywood and paint it 100%. Since it's not touching the ground and it's sloped, it will last many many years. I wouldn't put plastic over it as that will trap moisture and cause premature failure. Several coats of good exterior paint is your best bet.

 

[peterdaly]

You could use something like this instead of plywood, or on top of thin plywood for a bit stronger surface:
SmartSide 3/8 in. x 4 ft. x 8 ft. Siding Panel - $25 per panel at my local Home Depot.

 

[bobby1017]

I used tar paper and roll roofing on mine, it is nice to have a dry area under the rack.

 

[SuzyAbbott]

We used porch paint with built in primer for our rack. Works great, no issues!