Help, quick question

[Alexphd1]

Looking for a little bit of help...

 

I need to bulk out externally on the block work approx 20-30mm around a window before rendering. I was thinking of using cement board (never used before). Any thoughts or suggestions on any other material? 

Edited June 16, 2018 by Alexphd1

[Declan52]

Deep scratch coat with plenty of Water on the blocks to give it a good amount of suction.

[Alexphd1]

It's k rend. 

[Declan52]

You can still put a scratch coat on beneath it.