hello i'm going to do somethig like what you have for my new home soon. its cool. sadly, not many contractor in sin can do this. still exploring the best way to achieve this effect. the original style came from this japanese master call tadao ando. the actual method is to precast the concrete slab and mount onto the wall. hdb will definitely not allow this. i'm exploring 1. cement board - screen a layer of cement over it and drill the 4 holes. 2. ask carpenter to do up the "boxes" and cement screen over it. lastly, if you like what you have. stick with it. this kind of style and treatment is an aquired taste. not many people appreciate and can have kind of treatment in their house. do you have any photo of yr wall?