Sand like plaster behind shower tiles. What was he thinking?

[Talisker74]

Hi All,

I had removed a shower fitted by previous owner of my property. Two sides of the wall where the shower was were tiled. Once I had removed the shower surround and base I could see that the tiles were bulging in the middle... so i began chipping them off..

Well the bulge was 12mm of sand colour plaster ( light brown, disintegrates into a fine powder when rubbed), tiles were stuck on top with the usual white grout, plaster thickness ranged from mm at one side to 12+mm. Where the thick stuff was ( and there was tons of it) i could almost fit a finger behind it and the wall behind.

Anybody got any idea why this was done... I've taken it all off now ( didn't take much as it WANTED to come off!! ) and the walls are perfectly straight. Just nice hard dark grey plaster.

Im planning on putting up new tiles ( fitting bath ) but wondered... am i missing something here or is this just a colossal bodge by someone? I can't see how this would help waterproof a shower.. stumped.

cheers
Mark

 

[terryplumb]

do you mean the plaster was actually 12 mm thick or it had "blown off the wall" leaving a gap behind ? I assume it is an outside brick wall.

 

[Talisker74]

Hi Terry,

Both!! It was 12mm thick and had blown off. I got some pics on my phone... 2 sec and I'll upload them..

M

 

[Talisker74]

Here we go... Im no plasterer but this cant be right

Its a party wall.

 

[terryplumb]

that's a very badly applied bonding plaster ,unevenly put on ,and to a wall not primed before application, hence it has seperated. knock it all off mate.I think the grey is sand/cement .is the room on ground floor by any chance ?

 

[Talisker74]

Hi Terry,

Thanks mate! I figured something was trying to be achieved... even though it seemed wrong
Yep its ground floor. I hacked it all off this afternoon. Just smooth wall now.

I was just going to grout directly on to this but maybe that's not a good idea?

Cheers
M

 

[terryplumb]

is grey wall plasterboard or other ? I can't tell by pics. for info grout is what goes in between tiles on surface side ,tile adhesive goes between tile and wall .there are different kinds of both for different applications .steer clear of the diy types that say it does both.

 

[Talisker74]

Thanks Terry, I'll be sure to get grout and tile adhesive.

Well, when i was taking off the thinner parts of bonding plaster I accidentally nicked a mm or two of the grey stuff. It is about 1-2mm thick and there is a dark brown surface underneath. It has a sort of gritty texture. Certainly doesn't look like the brick in the rest of the house. My initial thought was that this was plaster over the brick and the grey stuff was just a skim... but i could be wrong obviously. It is certainly not plasterboard though.

One thing i do know, it is beautifully straight, i checked it with a 1.4m level and i'd have a hard time getting a sheet of paper in there!

cheers
M

 

[terryplumb]

ha ha, you got no excuses then for any tiles that are deflected !!

 

[Talisker74]

Haha,

Yea I was thinking this wall will be a dream to tile... but then its me that is doing it... so we will see
Worst case... if they fall off they might slice through an artery... but at least i wont be crushed to death under that bonding plaster

Thanks for your help Terry. Appreciate it!

Cheers
Mark

 

[vinn]

OP,
If you are still there?
From the details above it seems that your best bet would be to hack off back to bare brick, and then render a rubbed-up backing coat of 3:1 sand & lime mix.
Tile straight onto the render.

 

[Talisker74]

Hi Vinn,

Yep still about. What is your thinking for hacking it back to brick? Can I not just prime the wall with SBR first?
The left hand edge of tiles had parts with without that bonding plaster. It seemed pretty solid, took effort for me to chip off the tiles and then scrape off the adhesive. In contrast everywhere else it was a case of sticking the chisel down the back and the tile would pop of - or just pulling the bonding plaster to rip out a whole section.

Cheers
Mark