As per of renovation we plan to seal off the unused toilet sewage (maid toilet) and re-tile it over. However the ID said as part of the BCA requirement it is not allow to re-tile it over and can only cover it with PVC cover due to safety reasons methane gas release which sounds legit but will left expose protruding cover. Hence, would like to check if this is true cause other IDs that i'm checking in said can just re-tile and cover it no issue and what would be the implications that I will face? Smelly gas release if I just re-tile?