Though ply-board has been excluded from BS5385 it has been used for many many years with success when the correct grade was used. Is it not strange that two months ago we could fix to ply now we can't. Same adhesives out there still with "suitable to fix tiles to ply-wood" whats changed. If you have Flooring Grade or Class 3 ply-wood only, then tanking is the way to protect it.
