Plastering cement board

[marsaday]

Hello

I am using aquapanal and hardibacker board on my two sides of the bath/shower (using both as they fit the dimensions of the timber).

Above the shower area will be plaster up to the ceiling. So when the plasterboard and cement boards meet there will be a change over from tile to skim coat.

Can i skim into the cement board by say 10mm approx ?

I know i will need to skrim up, but will i need to prime ?

also i have some bond it pva solution so could use this the day before in this area.

Any advise ?

 

[PrenticeBoyofDerry]

I have previously skimmed over cement boards, much the same way as you are doing. By PVA prime (two coats) and multi-finsh
But Knauf do supply an aquapanel skim/filler coat, that is supplied for this purpose. http://manual.knaufdrywall.co.uk/knauf-products/page_866.html

 

[Karis]

I am using aquapanal and hardibacker board on my two sides of the bath/shower (using both as they fit the dimensions of the timber).

Not sure I follow your reasoning there!

Above the shower area will be plaster up to the ceiling. So when the plasterboard and cement boards meet there will be a change over from tile to skim coat.

It’s not usual to plaster above a shower area as it will be subject to extreme moisture & condensation which will cause problems, it’s usual to tile full height.

Can i skim into the cement board by say 10mm approx ?

Why do you need to make up 10mm? A few things here;
• You can’t skim finish plaster to a depth of 10mm, the average skim coat is 2-3mm thick you can go slightly thicker but I wouldn’t advise more than 5mm.
• Hardi say you can skim their cement boards but Aquapanel say you must use their own special & probably expensive plaster. I successfully skim Aquapanel with suitable prepping but only small services access panels, not full walls!
• Plastering is far from easy & getting a good finish is extremely difficult for a DIY first timer.

I know i will need to skrim up, but will i need to prime ? also i have some bond it pva solution so could use this the day before in this area.

You will certainly need to prime the cement boards with something. I don’t know what Hardi recommend on their boards but I prime Aquapanel with 2 neat coats of PVA the day before let it dry out, then I reactivate the surface with a mist spray immediately before I skim using a minimum thickness single coat skim. Not sure how it would stand up to moisture/condensation above a shower though.

 

[PrenticeBoyofDerry]

.

Can i skim into the cement board by say 10mm approx ?

Why do you need to make up 10mm? A few things here;
• You can’t skim finish plaster to a depth of 10mm, the average skim coat is 2-3mm thick you can go slightly thicker but I wouldn’t advise more than 5mm.

That's a fair point, that past me by. Misread/understood was thinking an area 10cm where plasterboard met cement board.
Maybe trying to level out wall to same as finished tiles?

 

[marsaday]

I was planning on going into the cement boards area by 10mm, not make out 10mm.

Ok, in this instance i may just take the tiles right up to the full height of the wall. I was going to stop where the shower screen finishes - approx 2m from the floor and then plaster the last 70cm section above the tiles.

But your comments about the wall above the shower / bath gets wet and damp means i will prob go for full tile here.

 

[Karis]

I was planning on going into the cement boards area by 10mm, not make out 10mm.

OK that’s clearer but 10mm won’t be enough to waste the skim coat under the tiles, more like 60-75mm.

Ok, in this instance i may just take the tiles right up to the full height of the wall. I was going to stop where the shower screen finishes - approx 2m from the floor and then plaster the last 70cm section above the tiles.

But your comments about the wall above the shower / bath gets wet and damp means i will prob go for full tile here.

I would.