What to do on underside of deck?

[lvl]

Hey guys I was wondering what most people do to the underside of the plywood they use for a new deck? I see some say just coat it with resin. Some say just resin will do nothing since it will crack and fall off. Some say you need to put a layer of csm.

I am using poly resin. Would just a good coat on the underside be OK?

Would that mean using PL premium not work to glue down the plywood?

I was also thinking of using epoxy with a thickening agent to glue it down?

Just not sure of the best method.

Thx

 

[Woodonglass]

Re: What to do on underside of deck?

If you are using Poly resin you MUST use a minimum of 1.5 oz mat. If using epoxy you MIGHT get by without using any mat but IMHO you should use it. You can use PL to glue your deck but I would use epoxy Peanut Butter. Must Stronger.

I'm just sayin...

 

[ezmobee]

Re: What to do on underside of deck?

Correct. Poly by itself won't last long before cracking. Using poly is fine but add some glass.

 

[erikgreen]

Re: What to do on underside of deck?

It doesn't actually have to be 1.5oz mat... use whatever is cheapest or that you have the most of. Keep in mind that the mat is only for waterproofing and protection, the main strength of the deck is from the plywood in this case.

If you want some stiffness/strength from the glass, you can put thicker mat, or mat with a layer of fabric on the bottom. 1708 is a nice choice for this. Some folks make the deck out of thinner plywood to save weight and cost, and make up the difference in strength (and cost with 1708.

Epoxy you can get away with no cloth or filler, but even that will last longer with something like milled fibers in it, or apply it on a thin layer of cloth (no mat required).

Erik