Hi KIaMing, there's a very active Facebook group for my neighbourhood and we have a very responsible HDB officer overseeing the cement screeding work. HDB requirement is for subcontractor to use pre-packed material to do floor rendering and apparently it's not uncommon for sub-contractor to use sands + portland cement to make more $$ out of it. The sub-contractor in my area also called up many residents requesting for additional payment of $$ to him claiming that our floor level is way beyond the 40mm that HDB would do for us. Quite a big huh hah and HDB officers are involved after residents filed complaint and email them photos where sand was seen being hauled to their unit for floor rendering. Main contractor was called in to top up unit with low floor level, after which sub-con will do up the floor rendering up to 40mm as per HDB spec. At the end the sub-contractor was ordered to hack all units where inappropriate material was used, and also to hack and redo a few units with extremely poor floor rendering workmanship.