Rendering Mix Help Needed

[leevis]

Hi
I need to render a small part under a window of my house (about 1m square) the majority of this area is made up of Aerated Block (3.6N) and some bricks.
Reading the internet there is about a bazillion ideas about the strength of the two coats that i need to put on. Some say i need to wet the blocks, others say i need to apply some SBR beforehand, some say apply SBR in the mix, then there is lime, some say use building sand or sharp sand other plastering sand.
Help please. I need to know what mix to use on both coats. Its a south facing external wall and i want to get started asap but really unsure as to the mix and the types of sand.
Anyone want to chip in with some advice?
Lee

 

[23vc]

Soak the blocks, scratch coat with waterproofer 5:1 plastering sand, top coat without waterproofer 6:1 plastering sand. Plasticiser in both.
SBR is more if you’re trying to bond the render to smooth bricks or something.
You can put (hydrated) lime in the top coat, for ease of workability, but I wouldn’t bother for this small area as you’d need to buy a whole bag.