wet plastering aerated lightweight blocks?

[phil090207]

I've built an internal wall of aerated concrete blocks. Ta-daa! For my next trick I want to wet plaster it.

I've heard the high suction of these blocks can cause plaster to crack. They do seem to absorb a lot of water very quickly.

What is the best approach to plastering. Do I need to use ALC plaster or is normal plaster ok? Can one-coat plaster be used? Do I need to coat the blocks with anything before plastering? Soak the wall with water perhaps??

Many thanks for some advice. Phil.

 

[noseall]

What is the best approach to plastering. Soak the wall with water perhaps??

Correct. Browning for the scratch and float coat and multi for the finishing coats. Skim the browning whilst it is still dark, i.e. before it dries out entirely.

 

[trowelmonkey1]

agree, give the wall a good soaking with water before you start with the browning though.

couldn't you just put 1 scratch coat of browning on and skim with finish noseall?

 

[noseall]

couldn't you just put 1 scratch coat of browning on and skim with finish noseall?

The scratch coat deals with initial suction, allows the float coat to be ruled off without drag and benefits when 'rubbing up'.
It is possible to lay a thick one-coat but saves little in time or hassle.

 

[trowelmonkey1]

ah, that makes perfect sense noseall! have done some walls in 1 coat and have found that i have to work at lunatic sppeds to get it on so that i can rule off before it's too late.

will do 3 coat next time and see the difference.

 

[phil090207]

Many thanks for your replies noseall and trowelmonkey1. I will give it a go using browning plaster on soaked blocks as you recommend.

Phil.

 

[grandwizard]

use gyprime to stop suction

 

[phil090207]

Thanks for the tip grandwizard.

 

[trowelmonkey1]

how does gyprime differ to PVA?

 

[grandwizard]

it differs because its made for these types of blocks pva is a bit hit and miss gyprime can be painted on any time

 

[trowelmonkey1]

think i might try it, often wondered, used knauf's plaster bonding agent last week for the first time, gives u a great key but not great for controlling suction