Get away with normal primed plywood to support shower tray?

[ChrisKingston]

Hi,

I'm redoing a shower and have built a sturdy 5 x 2" frame to lift a standard deep cast-stone Wickes shower tray.

I've read that you're supposed to use marine ply or WBP between the frame and tray. I'd need a whole full-size sheet to get a bit 760x760, which seems very expensive. I've got some decent ordinary 18mm structural ply square. I'm not in any rush so if I put two good coats of water-based acrylic undercoat primer on it, both sides and edges and screw holes once its screwed down, would that be ok? Or do I have to shell out for a sheet of WBP?

Thanks,
Chris

 

[longdogs]

I've used ordinary ply many times with a coat of Unibond. Never had any problems so far. If there are no leaks, the wood base shoud not get wet anyway. I agree that the price of marine ply is just outrageous.

If you are building a boat however, the best place to buy marine ply is B&Q as they supply the wood pre-warped which makes it easier to bend around the frame.

 

[Richard C]

I wouldn’t advise standard ply, the adhesive used to glue the veneers is not waterproof & if water gets into it, it’ll self destruct; you don’t need expensive marine ply either, exterior grade (WBP) ply is fine.

Standard PVA will do nothing to waterproof anything, it’s water soluble; in fact don’t use PVA for anything other than plastering in a bathroom.

 

[cumbriahandyman]

I wouldn’t advise standard ply, the adhesive used to glue the veneers is not waterproof & if water gets into it, it’ll self destruct; you don’t need expensive marine ply either, exterior grade (WBP) ply is fine.

Standard PVA will do nothing to waterproof anything, it’s water soluble; in fact don’t use PVA for anything other than plastering in a bathroom.

I'll second that...

 

[John506]

I've used ordinary ply many times with a coat of Unibond. Never had any problems so far. If there are no leaks, the wood base shoud not get wet anyway. I agree that the price of marine ply is just outrageous.

If you are building a boat however, the best place to buy marine ply is B&Q as they supply the wood pre-warped which makes it easier to bend around the frame.

Haha that made me chuckle!

 

[longdogs]

I wouldn’t advise standard ply, the adhesive used to glue the veneers is not waterproof & if water gets into it, it’ll self destruct; you don’t need expensive marine ply either, exterior grade (WBP) ply is fine.

Standard PVA will do nothing to waterproof anything, it’s water soluble; in fact don’t use PVA for anything other than plastering in a bathroom.

Yes, when I said ordinary ply, I did infact mean exterior as opposed to marine.

 

[Richard C]