Mr. Builder - Sealing Marine Grade Plywood For External Use.

[woodchopper]

Can you recommend an epoxy sealer for sealing a sheet of marine plywood for external use - it is to replace a sheet of master-board which the paint flakes off every year or so.
I hate pvc panelling btw.

[The Builder]

I know what you mean about Masterboard, Wooders. It's a great product, and easy to cut/use.
It can be primed to accept paint successfully, but I must admit I've tended to leave it un-decorated because of the risk of flaking. I just trim the joints and perimeters with uPVC cover strips.

However..... for ply: I rang a "boaty" friend about this. There are loads of single and 2-pack epoxy sealers. I use them mostly on floors.
Apparently, this is generally accepted as being one of the best...
(It's used a lot in Scandinavia, and they know about these things.)

https://www.makewoodgood.co.uk/product/cpes-clear-penetrating-epoxy-sealer/

It's made here now, and even available on Amazon.