Use your drill to make this job simpler.
Tile over plywood wall.
There are two materials commonly used for laying ceramic on plywood or osb that are applied before the tile.
Apparantly modern plywood has something in it which affects the tile cement i know from experience as i put on approx 10m2 of tiles before i discovered that they wouldnt stick to plywood however you can buy sealer which can be painted onto the plywood that makes the tiles stick on ok.
For wall installations plywood is overkill beneath the concrete or fiber board which is designed in five eighths inch material for wall settings.
To install the concrete board apply tile adhesive to the back then press it down against the plywood.
If you re not sure if you have lead paint test kits are available.
Concrete board concrete board also called backer boardcomes in 1 4 and 1 2 thicknesses and is usually sold in 4 x 6 sheets.
Shrinking and swelling will crack the grout can pop off tiles etc.
To be sure maybe drill up to 6 evenly spread out holes in the plywood at least 4mm deep or straight through in the areas to be tiled so the adhesive sinks into the holes and hardens hence creating a stronger fix.
Then you want to install screws into the concrete board in each of the holes.
While tile can be laid on plywood do not install tile directly onto the plywood subfloor itself.
Use intervening layers of two sheets of plywood.
Plywood is not dimensionally stable it can shrink swell and otherwise move around no matter how many screws are holding it in place.
Spread the mastic over a 3 square foot section of your installation area using a notched trowel onto the wall.
Either backerboard or concrete board is fine but i d recommend backerboard if it s for the wall as it s lighter it s also easier to.
Center your tile in the bathroom.
You may tile over existing tile painted or unpainted drywall plaster and textured walls.
If possible you should always use concrete board underlayments rather than plywood.
However tiling over tile can add quite a bit of thickness so make sure your wall can handle the weight.
No you can t tile to the plywood directly as wood is prone to warping.
The preferred method for tile installations is to use a sheet of underlayment.
Step 4 center.
When creating a grid pattern start at the center where the lines intersect.
There are tiling mats you can cover the plywood with decoupling mats such as ditra you then tile right over that.
You should not tile over wallpaper glossy surfaces lead paint or plywood.
Clean and heavily score area to where tiles are to be fixed it sounds like the adhesive does not have a rough surface in which to secure itself to.