SBR Primer on scratch coat?

[Lectrician]

Half my bathroom has been re-boarded with aquapanel and tiled.

The other half, or one wall, was plastered. The plaster came off with the tiles, leaving the cement scratch coat below. This is sound.

I had been told that tiling directly onto this is preferred, rather than onto the finish plaster. Looking at the BAL SBR, under priming instructions it doesn't mention a method for cement scratch coats, just plaster.

I called BAL directly and they have turned around and said you cannot tile directly onto a scratch coat, it has to be onto plaster? I have been told by many people it is preferred to tile onto the scratch coat and not the finish plaster!

What am I meant to do? Have it re-plastered? Use the SBR one part SBR to two part water and then tile onto the scratch coat?

I am now confused! Thought I knew what I was doing!

Thanks.

 

[Lectrician]

I should say, think it is a bonding coat as is pinky coloured and flat, no scratch lines.

Using ceramic tiles. Flexible adhesive.

Thanks.

 

[Gazzer]

If its plaster then no you cant tile to it. If its a render ( sand and cement ) then ok.

 

[Bubblecraft]

If its a bonding scratch coat, you cannot tile on this. A bonding coat will be dark grey when dried. Sometime finishing plaster is added to the bonding to dry it up quicker but doesnt really turn it pink. Pink will be a finishing coat. Sand/cement is fine but it would be easier to tile to a flat surface. If you re-sheet or put a finishing plaster on this, you can but allow a sufficient enough time to allow to dry. You will need to coat the plaster with an SBR primer before tiling

 

[Martino]

it sounds like browning by the colour of it....i would plaster this if it is browning.....you can tell by the strength of it....browning is quite soft compared to sand and cement.....if its browning dont tile straight onto...if its sand and cement go for it

 

[Bubblecraft]

Depending on the weight of your tiles, a fully cured plastered wall can carry up to 20kg per m2, inc adhesive & grout. A dot & dabbed plasterboard wall un-skimmed can carry up to 32kg per m2.
It's food for thought.

 

[Andy Allen]

If its a bonding scratch coat, you cannot tile on this. A bonding coat will be dark grey when dried. Sometime finishing plaster is added to the bonding to dry it up quicker but doesnt really turn it pink. Pink will be a finishing coat. Sand/cement is fine but it would be easier to tile to a flat surface. If you re-sheet or put a finishing plaster on this, you can but allow a sufficient enough time to allow to dry. You will need to coat the plaster with an SBR primer before tiling

thought bonding plaster came in grey or pink..??

 

[Bubblecraft]

Browning can come grey or pink, bonding is grey. I've yet to see or use it in any other colour

 

[Lectrician]

Thanks for the prompt replies, thats great. I posted this while at work, and now I am at home, I can see it is a sand and cement scratch coat, which doesn't surprise me as it was done in 1978 by the age of the house, and the tiles and bathroom were original to that!

The pinkish hue is from some remenants of finish plaster. What didn't pop off with the tiles I removed. It is a solid and true finish, perhaps a little grainy/dusty if you pull a tool along it hard.

A builder chap I work with said it was preferreable to pull the finish plaster off and go direct onto the sand and cement with a primer, and I didn't question this as a couple others had said to go this way too. It was only when I spoke to the girl in technical at BAL that I had jitters.

So, as it is sand and cement, and is firm, would you prime it? 2:1 BAL SBR?

Pics:

 

[Bubblecraft]

Tiling on to the EXISTING finishing coat plaster is a no no. With the finishing plaster coming away when removing your tiles, this shows your plaster has blown. I'd use a 2:1 dilution of SBR. The girl from BAL probably thought what I thought. New plaster fully cured, yes. Blown plaster is no

 

[Two-Trowels]

Browning can come grey or pink, bonding is grey. I've yet to see or use it in any other colour

Must be a regional thing. In the South we used to get all Carlite type plasters in grey or pink, for a while now everything has been just pink, including Bonding - I've not seen grey Browning (hard wall) or Bonding in grey for a long time.

 

[Dougs Third Go]

Browning can come grey or pink, bonding is grey. I've yet to see or use it in any other colour

bonding comes in pink too.:smilewinkgrin:

 

[Dougs Third Go]

if it is indeed sand and cement render then yes, prime it to consolidate any dust and tile it.

 

[Bubblecraft]

Never seen bonding in pink. Might be a regional thing

 

[Diamond Pool Finishers]

Never seen bonding in pink. Might be a regional thing

it is a regional difference Bubble !! depending where the gypsum is quarried in the british isles ............