Options for waterproofing plywood boards


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Established Member
17 May 2012
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South West Wales

I'm going to be putting some plywood boards in the loft for a water tank base. I want to get it from B&Q because time is of the essence and they'll do all the cuts for me. They don't do marine ply, and I'd feel safer if the boards were waterproof in case there was ever a slow leak.

I'll start with a couple of coats of woodworm killer to be on the safe side. Then what? A quick google throws up loads of options and gets my head spinning, so I thought I'd ask the wood experts in these parts...

The quicker the better, so any one coat systems get bonus points! Quick drying would also be a great feature. In fact, if there are any woodworm treatments that waterproof as well, that will get pole position/gold medal!

I'll be getting the boards tomorrow and most likely fitting the Monday.

Your thoughts would be most appreciated.

Many thanks
Glad to hear I'm over-thinking it / over worrying. It's just that some of the stuff I've been reading said you must use marine ply, it must be waterproof, etc etc. And obviously getting it wrong could be catastrophic, so I just wanted to check as once it's done I don't want to be doing it again!

I was also thinking the waterproof chipboard stuff could be suitable (Egger protect or Cabershield P5)
You could also throw some roofing paint on it (like Black Jack) - that will make it totally waterproof I would have thought
I did have similar thoughts to other people however - best to focus on leak prevention :D