Hi, I wonder if any professional tilers can help me please?

I had a dormer conversion to my bungalow carried out last year and am getting around to completing the upstairs bath/ shower room.

the shower is goingto take the form of a wet room, with a showere sormer being set into the floor and three walls tiles. one of the walls is to a reduced height and the ceiling slopes down to that height.
I would like this sloping ceiling to be tiled as part of the wet room.

I have had 4 guys round to price the job, one was quite candid and said the job was not in his area of expertise, one only visited for a few seconds, gave me quite a sensible price, one looked at the job and didn't think there was a problem, but the fourth (and I must admit, I was impressed with this guys Professionalism) said he wouldn't want to tile on that surface.

When I asked him why, he said that he thought the ceiling had been constructed from polyfoam linerboard or Thermaline board.

He explained that the board as probably up to 3 inches thick and screwed to the rafters. The tiles I want to use are 600x300mm porcelain tiles.

He thinks that the weight of the tile will just rip the plasterboard off the insulation board.

Is this correct and what is the alternative?

He suggested removing the board and constructing timber studding over the rafters to mount the board ( I think he said Matrix or Marmox, but I might have misheard) and filling the gaps in the studding with Kingspan to regain the thermal insulation.

Many thanks for your help

Sounds like the best advice has come from the last guy. Of course you'd need to investigate what the substrate is first but yes you could have problems regarding the weight issue

There are cheaper tile backer boards out there but Marmox is a good choice. No doubt the last guy will be more expensive when you compare quotes but the signs point to him doing the job correctly and only the once! Get a wetroom wrong and falling tiles will be the least of your worries!

As above, the last guy seems a knowledgeable tiler

...and Marmox is already waterproof, just need to seal the joints properly!

yep, last guy gets my vote.