Advice on rendering lightweight blocks

BadgerF8

New Member
Evening all,
I have built an extension which is in lightweight blocks [Ytongs] which are fairly smooth. I am intending to two coat render 4/1 scratch [with or without waterproofer/SBR?] and 5/1 top coat. Now I have done a fair amount of plastering and some rendering but I want to get this right!

The more I enquire the more different approaches plasterers use! My main concern is the fact they are smooth [ish] there is no scratching on them so I know I will have to key them. But should I prime the wall or just wet it? And what additives should I use in which coat? I suppose its about 30m2 to do and the plastering sand is already here!
 

Dgplastering

New Member
Hi badger, if the blocks are thermalites (thats what they sound like) you will need a scud coat or id use micro gobetis a parex product to kill the suction. You van always check the suction by chucking some water on them and seeing how quick they dry or do a test panel scratch coat and see how it goes off
 

johniosaif

Private Member
I would use a render grit or sbr if there smooth , the mix ratio should be at a max 5/1 and 6/1 top coat
 
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