If you're not going to apply any paint or other preservative then you must use marine grade ply or similar which is already pressure treated with preservative. Any particular reason why you won't be painting or varnishing the bench though?
"Any particular reason why you won't be painting or varnishing the bench though? "
The previous bench lasted 20+ years without being painted and I was hoping that this one would too.
It seems that marine ply is considered to expensive to stock ( or maybe i'm frequenting to low a standard of plywood supplier ). I'm nearly certain that I used it on the previous bench.
I've been offered 'WBP' and also 'shuttering grade' .
What are these, and would they be suitable ?
Anyone suggest where I could buy small amounts of marine ply around Dublin ?
<edit> ooops, Badge55, didnt see your post before I posted this. Confirm runoff slope has been provided. Do you think that WBP is the best that I'll be offered ?
I also tried to buy marine ply in B&Q and was told "nobody buys it so we don't stock it" and I used WBP or whatever it's called but I was only building a 'boxing' in a bathroom which would be tiled over anyway.
Waller and Wickham in Baldoyle Industrial Estate sell Marine Plywood, as do Noyeks Newman. Like anything with the word 'marine' in its description, it ain't cheap.
Marine ply is a far superior product to WBP, but you'll need to go to the 'proper' builder's providers to buy it.
As mentioned above, WBP stands for water and boil proof, but this refers to the glue, not the veneers. So repeated soaking and drying will result in it delaminating.
Leo
Looking at Woodworkers web site, they have 8" x 4" 'Birch Plywood Weather and Boil Proof (WBP)' 18mm for € 60.50 and 18mm Marine Ply is cheaper at €53.31. While the 'WBP Chinese Plywood' must be the standard cheap stuff builders use is €29.40