treating plywood

[jupiter_19630]

I recently treated a sheet of 8 x 4 18mm exterior grade wbp ply with creocote treating all edges and faces with 2 coats. However the ply has now started to seperate.
After complaining I have managed to get a replacement sheet. The sheet is to be used as the floor for an outdoor aviery. Obviously I don't want this to happen again. It has been suggested I treat the edges with Varnish.
Good idea or bad idea? what about the faces? treat or not? and if so what with? Creocote or some thing else? Any advice would be greatly appreciated.

 

[gregers]

wpb as far as i know is only,moisture and boil proof,if you want exterior quailty then get marine ply.

 

[Deluks]

Doesn't creocote contain solvents? may have affected the glue in the ply. Best use something less watery, and creocote is probably harmful to the birdies, plus it gives off a stink.

 

[Patochik]

WBP = weather & boil proof, but this refers to the glue line only and not the actual veneers, for example most softwood/shuttering ply has WBP glue but us made from an inherently perishable speices veneer. Marine plywood still has WBP glue line the same but to confirm to the marine spec (BS1088) it must have a single peice face veneer (no joints or plugs) and core gaps are not allowed.

Marine plywood, just like any other exterior plywood, still needs the edges (at the very least) sealing to prevent moisture ingress through the end grain of the veneers. Sounds like you have a faulty board originally as if correctly sealed the board shouldn't have delaminated like you describe.