No SBR

[opps]

Hi all,

SWMBO became bored with waiting for me to redo our downstairs bathroom so she commissioned a plumber and the tiler that he recommended.

I used my Festool masonry renovator to grind away any tile residue and the existing water based eggshell on the walls.

Once the plumber finished I PVA'd the chases and filled them with bonding plaster. I made sure that I didn't get any PVA on the surface of the old plaster, I didn't want to create any potential problems for the tiler.

The tiler started yesterday. Thus far, his cuts and levels seem good. I am however concerned that I can see no evidence of him having used any SBR on the walls. If I lick my finger and touch the walls just above the last row of tiles that he has fitted, the plaster turns from a light dusty pink to a dark pink.

It may well be the case that he pre-wet the walls before applying the adhesive but is that really deemed to be acceptable? Given that I had grinded the walls, the finish was extremely porous, ie more so than when the room was first plastered.

The walls are thermolite with a cement screed and then a plaster skim. The tiles are 600*600, 10mm porcelain. I forgot to check to see which powdered adhesive he was using.

I had assumed that he would tank the shower area and "shampoo bottle recess" but I guess he isn't planning to...

 

[Paul C.]

You have several problems.
1. Cement based adhesive is not compatible with gypsum plaster unless properly primed with SBR or Acrylic primer (Not PVA). Ettringite crystals will form from a reaction between the wet portland and gypsum, and prevent a proper bond between the wall and the addy.
2. Showers and wet areas must be tanked. This is now part of British Standards and without tanking, your warranties for the fixing materials will most likely now be null and void.
3. Your chosen tile will be way too heavy to fix to plaster. Plaster and plaster skim has a limit of 20kgs per sqm. Your tiles including fixing materials will be around the 27-28kg mark.

Sorry, but sounds like your tiler doesn't have a clue!

 

[opps]

Thanks PaulC.

1. Yep, I am aware that PVA should not be used. "Ettringite crystals"- I was unaware of that, thanks.

2. I was unaware that showers now have to be tanked. Again thanks.

3. "Plaster and plaster skim has a limit of 20kgs per sqm."- I have always wondered how they calculate that. Are the figured based on the load bearing once the substrate is tilted horizontally? It has been an awfully long time since I did my A'level maths. Wouldn't the vertical load on a vertical wall be less than 20kg per 360000mm² ?

To be honest, the above aside, I am not particularly impressed by his tiling now that he has finished. Some of the cuts at the top are 6mm short and it looks that where he has need to trim tiles he did them free hand on a cheapo macalister wet blade cutter with no fence. The snap and score cuts were done on a 700mm Rubi and look fine (bar where they are short) but the cheap wet blade cutter has left lot of chips which he decided against dressing. The meeting edges on some of the tiles are out of kilter as well, by that, I mean that you can feel an obvious step.

He hasn't siliconed the shower tray or the corner of the wall where the shower will be. TBF, I guess that may be because the didn't want to have to come back the next day once the grout had dried.

My concern is that the plumber, when fitting the enclosure will only seal the visible areas once he has fitted the enclosure, ie. not the bit under the profile of the vertical tracks.

Perhaps I need to silicone the tile/tray and corner before the plumber turns up.

 

[Ernesto Di Michele]

Your plumber will more than likely put some silicone behind the profiles during installation. Saying that, this is a very common installation fault. Definitely better to silicone tray before shower door installation however.