New bathroom floor

Bergaspeed

We need to lay a new bathroom floor as the old one has rotted away in one place and now has a hole in it. The floor is tiled and under the tiles it looks like chipboard -the previous owners certainly did things on the cheap!
What do we need to lay the new floor with so that we can lay new tiles on top of it. and how do we do it.
Somebody had mentioned a waterproof membrane is needed - is this correct?

andyhop

25mm plywood glued and screwed to the existing joists

Stick extra timbers in on all unbraced joins

A tanking membrane is not really required unless its a wet area

Fire_Fox

You might consider marine ply which is waterproof, don't see why you'd need a membrane providing the tiling is of a high standard with waterproof adhesive and grout.

absent_dad

You often find in new builds (last 15/20 years chipboard t&g flooring, it's a real pain as it squeaks and once wet turns to mush, I refer to it as weatabix.

If this is the case in your bathroom your best bet is to have it all up and as said replace with either 25mm ply or suitable flooring (more chipboard but see below or std t&g pine planks)

What you have to remember is that when laying tiles the floor cannot move, ie no springiness, else the grout and eventually adhesive will fail and the tiles will pop off.

If you are on a budget (ply is really expensive now) cut out the rotten chipboard and replace with a similar piece then go over the whole lot with 6 or 9 mm ply, this will strengthen the floor, glue and screw (and make sure you screw right through to the joists...take care where the pipes are) it all down so it is rock solid.

You shouldn't need a membrane unless you are making a wet room.