sealing plywood

[kevin67]

does antone know why bal recommend sealing the underside of plywood and not the face. i always seal the underside but was just wondering why this is.

 

[tfs]

I imagine it would be to eliminate moitsure from beneath the floor boards affecting the ply. Hot, cold or moist air is under the floor boards due to ventilation requirements. The top side of the board should be protected by the adhesive and tile although I would prime this side of the ply to.

I havent read any guidelines by bal stating this so dont have an exact answer (I will have a look now that you have mentioned this though!)

 

[tfs]

actualy the only way i think you wouldnt need to seal the top face of ply is if your fitting backer board over the ply as I reckon water could still penetrate through the grout or adhesive as cement based products would deffo be porous