Tongued and Grooved P5 Floorboard

tt2cno

Hi all, first post here.
I am doing a kitchen extension and my builder is fitting T&G Chipboard P5 floorboard to the floor. The floor would be tiled over. The T&G floorboard is the 22mm kronospan P5 type, which my builder says is moisture resistant. Can this type of floorboard be used in wet areas like kitchen?
I would appreciate some advise please, I am concerned about the water resistance of the board since chipboards appear to swell in contact with water.
Thanks

docmatt

If it's tiled over properly it won't really matter.

Homersimpson

P5 grade is the moisture resistant grade, its usually slightly green in colour (but not always).

docmatt

Homersimpson wrote: »

P5 grade is the moisture resistant grade, its usually slightly green in colour (but not always).

Yeah I had a barmy with my supplier saying they didnt send me the green stuff which is what i ordered. Turns out they don't green them any more to save the environment as the green was just the dye and not the moisture resistor which is actually a clear additive!

keystone

P5 is not suitable for tiling over directly - its not just a question of moisture resistance, its also a question of movement. Even a decoupling membrane over chipboard isn't 100% guaranteed.

Any chipboard should be overplyed first (min 12mm) and in that case its a waste of time and money laying the chipboard in the first place. 25mm WPB ply directly onto the joists and tile over that is the only sensible way forward.

Cheers

keystone

docmatt wrote: »

If it's tiled over properly it won't really matter.

That, to me, is a contradiction in terms.

Cheers

phill99

docmatt wrote: »

If it's tiled over properly it won't really matter.

Keystone is right - thats a stupid comment. Of course the substructure matters. If water ever permeates through, the whole floor will rupture, whereas if you use P5 and water does somehow get under the tiles, then it will only bring the tiles off and not require a whole floor replacement.

tt2cno

phill99 wrote: »

Keystone is right - thats a stupid comment. Of course the substructure matters. If water ever permeates through, the whole floor will rupture, whereas if you use P5 and water does somehow get under the tiles, then it will only bring the tiles off and not require a whole floor replacement.

Many thanks for all the contributions. It would appear 25mm ply is the way to go; will discuss this my builder.