L
LM
Your only supposed to prime the back face and edges of ply with an SBR to prevent moisture ingress, that is of corse if you've used WPB or Marine grade plymy only fail with ply was an 18mm bath panel which i forgot to prime... banana within 2 days. but there is my proof that 'live' material works.... ply works.... a bath panel if primed on both sides and then tiled can last for years and years standing vertical with little support....
as I am experiencing when the keraquick sticks to the plasticiser primer..... its a total swine to break the bond.