Hi guys, a basic question, we have some kitchen cupboards and under counter areas in the new house build that are still raw AAC Blocks. The original idea was to have these areas tiled, however I have changed my mind on that and just want to plaster skim the walls, primer and paint.

The rest of the house was cement rendered, and then plaster skim coat was applies, sanded & primed.

I understand that these terms (render, plaster, skim coat) seem to get get used interchangeably here, however in AUS where I am from, and subsequently in my house build, and this post, cement render is grey cement applied and smoothed onto the bare AAC blocks, plaster skim coat is a thin white plaster layer applied on top of the render to remove any roughness, which is then sanded to a smooth finish and primed prior to painting.

 

My question is, can you plaster skim coat directly onto AAC blocks and bypass the cement render stage? As mentioned, these are inside cupboards and under counters, which will rarely be seen.

Any thoughts would be helpful.

Cheers!

Cement Render

 

Plaster Skim Coat

No.
You always need the scratch coat (render)

4 hours ago, Slowhand225 said:

No.
You always need the scratch coat (render)

Thank you, however it would be more helpful if you could elaborate as to why that is required?

Nah, just paint it with latex paint a few times until you get the surface you want. That's what I did and works fine. No need to complicate things...

18 hours ago, firewight said:

Thank you, however it would be more helpful if you could elaborate as to why that is required?

Because without it your skim coat will fail eventually. The skim coat needs to bond to the scratch coat, the skim coat will not stay on the cured blocks. 
Just for clarity, the skim coat and the scratch coat are NOT the same material.

I know you said its behind the cabinets and under the counters, I can't do half arsed work so if i'm going to do it, its going to be correct.
However, not everyone sees it like that.
Could you do without it, probably.

Is that a double wall or the thicker blocks ?

 

I'm happy with my double walls , no more hot walls.

 

Is that a thin heat shield in your second pic (ceiling) ?

Not enough , use the thick rockwool .

https://www.homepro.co.th/p/213896

I think that:

Skim-coat dries, while render cures. 

Skim-coat shrinks, render does not. 

 

 

On 8/26/2025 at 9:26 AM, FlorC said:

Is that a double wall or the thicker blocks ?

 

I'm happy with my double walls , no more hot walls.

 

Is that a thin heat shield in your second pic (ceiling) ?

Not enough , use the thick rockwool .

https://www.homepro.co.th/p/213896

 

Its double 7.5cm AAC blocks with a 5cm air gap. The thing you are referring to as insulation is just a water barrier, its not being used as insulation. The roof has 5cm bonded PU foam to the metal roofing sheets, as well as 15cm on-ceiling insulation, so we are well covered for insulation but thanks.

On 8/27/2025 at 4:21 PM, Yellowtail said:

I think that:

Skim-coat dries, while render cures. 

Skim-coat shrinks, render does not. 

 

 

Thank you, this was very helpful.

Does anyone know how much cement thai builders use in the plaster for a m2 wall. Just approximately