I'm about to tile my bathroom floor. Chap in the tile shop said the floorboards should be covered in half inch marine ply. Wickes "good ideas" leaflet says 18mm exterior grade ply.
Can I take the easy middle route and go for 12mm exterior grade ply, or am I asking for trouble?
Cheers, Andy
The object of the game is to remove the movment between the floorboards, and any bending.
For example, floorboard size strips of ply are not idea, getting it covered in a single sheet, is much better.
The thicker the ply the harder it is to work, cause it gets heavy, the thinner, the less usefull it is.
Rick
It also depends on the size of the joists supporting the floorboards. I live in an older house where the joists are 9" x 3" over a 12 ft span. My bathroom floorboards were covered with 3/8" exterior ply and the tiling is still perfect after 8 years. Newer houses tend to use 6" x 2" joists so I would say the Wickes recommendation would give a better long lasting result.
They all say marine ply, but that's because they don't know what it is. Use 3/4" WBP or exterior grade ply. But deff. 3/4".
Might as well remove the floorboards altogether and end up with the same level at the door instead of an annoying little step.
To tile over wood you need to take the flex out as much as possible.
A lot depends on whats underneath - joist sizes etc.
Ply is generally felt to be strong and provides a level surface.
Then lay on a thick (10mm or more) bed of flexible cement.
Grout may still crack a little. But tiles will stay stuck.
Indeed. my upper floors ar 18mm chip. On fairly substantial joists. Tiled obver that bare. Did have problems with first extremely quick and dirty tiling- water got into wood, swelled and cracked tiles off, also some cracked from flexing.
Redid with thicker tiles, much thicker, flexible cement, and fixed the dripping flush pipe on the toilete. All is sweetness and light.
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