I'm not really saying they're necessarily using it to 'add' rigidity, - - I'm just saying that it doesn't, - - and in this case more rigidity is called for.reveivl said:Cement board screwed or nailed to the sub-floor (not the joists) is not used to add rigidity
reveivl said:Cement board screwed or nailed to the sub-floor (not the joists) is not used to add rigidity, it is used as a de-coupler, to separate the tile and it's mortar from the different expansion rate of the subfloor. Your floor must be rigid enough to support the tile regardless of the cbu.
As to your question Flor, you need the span of the joists from support to support. And the depth of them. Also, what tile? Granite eg needs twice the rigidity than ceramic floor tile.
All that having been said I sure would add 3/4 ply to it. :cheesygri Rich.
Been putting tile (ceramic) directly on 'layered' plywood (1 1/4" minimum) with Flex-Bond for 26 years now, - - no failures.HuckabayHolding said:NEVER over just plywood or it will fail.
K custom home said:Never put a quality tile or stone job on wood. Expansion of plywood will start to pop the grout sooner or later. Tile and stone have been set on concrete for a hundred years for a reason.