I am redoing my sun pad ,,,I need to get some 1/2 plywood,,do I have to use marine grade plywood or can I use exterior grade plywood??or how about pressure treated plywood??
it will be covered with foam and vinyl

Thanks

Use the best wood you can get your hands on and then I would even coat it in multi layers of polyurethane for extra water resistance and durability. It gets caught in the rain, or from swimmers in/out of the water etc. and the water moisture will linger under the foam. It has to be durable.

Good luck, sounds like a fun fruitful project.

I would coat it with at least 2 coats of fiberglass resin.

I would use that plastic PVC type stuff, I forget name... I am having XT use that in whole interior of my Cig, I dont want any chance of rot as I intend to keep boat for a long time...

My whole interior is being redone in synthetics. No more real wood to worry about.

My friend does upholstry for a living and he coats everything with fiberglass resin to seal it. He does not use marine grade wood - it is not necessary when you coat it with resin. The wood does need to be dried.

no wood !!!! use starboard

+1

I would not use any type of wood in your boat. after the cost of quality wood and resin you could buy pvc king starlight or even king starboard for your application and it will last a life time...

remember to drain well the more air the better.

Starboard now makes a lighter weight version of it. If you do a swim pad it is a much better choice as the regular stuff is WAY heavier then wood and puts a load on the harch motor. If you go with wood and use resin then I would thin it out so it soaks in. It can be hard to drive staples through resin and once you make the hole with the staple then you have made a place for water to go in and get trapped in there.