My plaster is crumbling in old bathroom, can I render the wall and tile on that?

[Gary111]

Hi, Ive got an old house with crumbly plaster in the bathroom, it seems like plaster is not the best material to tile on, and I can't plaster straight and level.
Is it a sensible option to try and render the wall and tile straight onto that?

Being an old building it seems to have some historic movement.

Thanks

 

[blup]

Boarding it is an option, with suitable moisture resistant board, you can insulate at any outside walls if space permits

Blup

 

[opps]

Over boarding makes sense if you drill into the bricks.

 

[mrrusty]

Crumbly plaster isn't a good idea for tiling in a bathroom. Knock it all off back to brick/block. Board it using either dabs or foam adhesive. In the wet areas use cement board, the rest plasterboard is fine. Use some screws and plugs in the boards as well for a really firm fix (and screws help level the boards if using foam, as it can expand and push the boards out). Take care to get the boards super-flat and your tiles will go up like lego.