remove chipboard?

[rachel]

Hi - I posted ages ago about dodgy tiling/shower installation done in a loft conversion.
Finally we're going to have the whole thing redone (not by the original builder!).
We've had different people quoting for the job but I'd like to run sth past members of this forum

Dodgy builder put chipboard on the bathroom floor and tiled straight on top + the shower tray is not supported enough (it's resting straight on the joists).

We've had different installers/tilers quoting and:

1. Some say they can't remove the chipboard and will add 18mm WPB ply on top of the chipboard. This will lead to us having a step into the bathroom.

2. Some say they can cut the chipboard and replace with 18 mm WPB ply.

We'd rather not have a step into the bathroom so we'd prefer to go with solution 2 but we are not sure how realistic it is, especially as some apparently good people told us they just wouldn't be able to do that.

Could anyone on here with experience on re-jobs with chipboards in loft involved give an opinion??
If putting WPB ply on top of chipboard does the depth have to be 18 mm or could it be less (to make less of a step from the ensuite to the bedroom part)?

Many thanks in advance

[Rich]

It is hard to say without seeing the room. If the tiler is going to overboard using ply than it must be a min 18mm boil and water proof marine grade ply. Is there much movement in the chipboard? If the floor is solid, or you can make the floor solid by screwing down into the joists then I would over board with a cement board, these are much better for the purpose and will only add 6mm rather than the 18mm ply.

But the floor must be made deflection (bounce) free before installing these boards as they provide a brilliant surface to bond to but they will add no strength to the floor, any bounce in that chipboard and you will have cracked and loose tiles.

Have a look at the link below, might explain them a little better and give you other members views



Plywood floors...

[tilerjason]

great advice above, tile backing boards are cement boards are all i use . also dont be afraid to ask your tilers / builders for two or three reffs, do a bit of home work about them first, even try googling them youll be suprised what you can find out. when your paying out money you deserve to get it done first time and done proper

[diamondtiling]

I would remove the chipboard completely and start from scratch using 18mm ply with 6mm backer boards, I would incorporate a tray former and use aqua panels around the shower or wet areas.
Get the prep right now and you will avoid many problems.