Best adhesion?

[Curmudgeon]

Hi all,

Looking for some good advice, I have to plaster up some fairly rough bricks with a good sand cement base in a new shower area to then take an applied Crommelins waterproofing layer prior to tiling.

In places this base will need to be a good depth.... say around 20mm or more. I want to make sure I achieve good adhesion and never get the hollow drumming of the base coat coming unstuck from the bricks.

I'm thinking of a fairly liberal use of a PVA additive, like Unibond or Bondcrete both in the mix and on the surface prior to application, I'm also thinking of using a fresh lime in the mix too, hoping that this will add a bit of flexibility to the mix.

Firstly is this a good plan and what would be the best ratio's if I do this. ?

And Secondly, is there something I could use to fill out that depth better, like Compressed Fibre Cement Sheeting or Aquacheck plasterboad... or would that just be making un-necessary work. Should I stop worrying and just start slapping my mix on the walls?.....

Thanks for your time all.

 

[johniosaif]

You could paint on an sbr slurry mix, mixing two parts cement with sbr and painting it on the brickwork, the next day apply a coat of sand and cement mix ratio four to one with a good waterproofer like sika or sovereign

 

[Curmudgeon]

Thanks Johniosaif,

Umm... pardon my ignorance, but SBR is that some sort of a liquid rubber solution?

I like the sound of this advice, but as I'm in Aus.... I need to find the type of product that fit's the bill, that is available here. So if you can describe it I should be able to track it down.

Cheers

 

[flynnyman]

Wet the brickwork and give it a scratch coat to get it pretty straight, topcoat it the next day job done and welcome to the forum.

 

[Runswithscissors]

Hello Mate

Get in touch with Knauf in Aus..... ask for them to talk to you about Knauf Permarock (we call it Knauf Aquapanel in Europe)

12.5mm thick 100% cement board....... the Internal board is specifically for tile backing! PERMAROCK® | Knauf Australia

it is designed to be fixed to metal studs or timber.... but can be fixed back to blockwork with rawl plugs and screws (talk to Knauf about the screws as well....) https://www.knaufplasterboard.com.au/uploads/resource-documents/KNA_Permarock_web.pdf

If they are not comfortable about talking you through the application, drop me a mail at [email protected] and I will help out and cc in their technical office...... (it is specified as a board for studs... so not sure if they will have expierience of fixing it to blockwork)

You probably will not then need your lining before the tiles then..... unless it is a complete wet room, in which case the lining will be advisable!

Good luck!

 

[Runswithscissors]

Where are you based?