Shallow filling of block / wood surface for tiling

[rivergo1d]

Hi
I have almost prepared my sand/cement wall for tiling by hacking off the old skim coat. The sand/cement seems very well attached for 99% of the area. There are now a couple of problem areas, shown below.

The first picture is above the door. It is two very solid wooden battens covered by wire mesh, and the sand/cement on this has mostly come off. Depth relative to neighbouring sand/cement is about 10mm.

The second is an area at the bottom of a wall, with bare blockwork. Depth varies form about 8mm to 15mm.

Both areas are each no bigger than 90cm x 20cm. The tiles are 30x60, to be laid with the long edge horizontally. Tiles are pretty heavy, about 20Kg\sqm, but for these small areas I'm happy to take the risk with new basecoat etc rated at 20Kg/sqm (am aware grout and adhesive counts extra).

Just wondered how these areas are best prepared for tiling? I see 3 options ... room width is very tight, so boarding over is not an option.

1. Should I just leave it for the tiler, who may be able to build up layers using tile adhesive? Will that work on the wood/mesh?

2. I have a plasterer coming in anyway for the ceiling, should I ask him to hardwall it? Is 8mm too thing for this?

3. Or could I dot and dab some hardiebacker on for this small area? I am concerned that having part hardibacker,, part sand/cement could lead to cracking where the two join.

Thanks for any advice you can offer ..

Untitled

• rivergo1d
• 5 Jun 2011
• 1

Untitled

• rivergo1d
• 5 Jun 2011
• 1

 

[Richard C]

The tiles are 30x60, to be laid with the long edge horizontally. Tiles are pretty heavy, about 20Kg\sqm, but for these small areas I'm happy to take the risk with new basecoat etc rated at 20Kg/sqm (am aware grout and adhesive counts extra).

Them’s big tiles, have you checked that weight; best not guess it!

1. Should I just leave it for the tiler, who may be able to build up layers using tile adhesive? Will that work on the wood/mesh?

Cement adhesive can be built up to around 10mm when local filling but what your describing doesn’t fall into that category; doubtful. Be careful with your tiler, some don’t have a clue what they are doing & you may not find out until it’s too late.

2. I have a plasterer coming in anyway for the ceiling, should I ask him to hardwall it? Is 8mm too thing for this?

Bit confused, are you intending to tile the ceiling? Hardwall or any base plaster bar one is not a suitable tile base; render will work but you will have to wait around 3 weeks for it to cure before tiling unless you use a quickset render.

3. Or could I dot and dab some hardiebacker on for this small area? I am concerned that having part hardibacker,, part sand/cement could lead to cracking where the two join.

You can’t join them; if you have adjacent dissimilar materials, there is a huge risk it will crack. Either separate them with an expansion joint (impractical on a wall) or overboard the lot with a backer board if you want to avoid.

 

[rivergo1d]

Thanks for the reply Richard, good to have some knowledgeable input. I thought I was just being paranoid about option 3.

The tile weight IS 20Kg/m2, so I'm looking at about 24 with adhesive and grout (which is why I went to the horrible trouble of hacking off the plaster skim, glad I did, some was very poorly attached).

The ceiling is being skimmed (took down some coving) but not tiled. Thought while the plasterer was in, I could get him to sort out these two patches on the walls.

So it looks like option 2 - plasterer - is the only realistic one. Could I ask, you say all bar one are unsuitable for tiling on ... what is that one option we should we be using then? He seems to be resisting the rendering option ...

Thanks
Richard

 

[Richard C]

Plaster is not a good tile base mainly because of weight restriction which can be a problem with large format tiles. Base plasters with the exception of Thistle Dri-coat are unsuitable but it’s cement based as opposed to a Gypsum based plaster intended for use after damp proofing & not specifically tiling; Ive never tried it in this situation.

Your plasterer maybe shying away from rendering because it’s not so easy to do & I would not be at all surprised if he has no idea that base plasters are not suitable for tiling. If you do get him to render it, you must leave it to fully cure before tiling over or may have problems.

 

[rivergo1d]

Thanks Richard