According to your choice of expansion bolt determine drilling depth, notice board plastering layer and protective layer basically not what strength, must the drilling structure layer, but the board structure layer thickness is about 10 centimeters, not drilled.
Although the plate reinforced sparse, but does not rule out you just drill bit in the reinforced position, into the floor 3 to 4 cm (if the plate is not plastering is 1.5 centimeters), if the drill will significantly hinder the sense, at this time suggest you pan 2 cm drilling hole position.
First of all, the slabs and beams are sufficient to withstand the load of ceiling fans. As the plate steel is relatively sparse, good drilling, so fixed on the board better.
1, to choose the drill bit, I have done similar things, at first I choose steel drill to drill concrete, think it will be faster, but not actually, but more difficult. When the stone is changed, a few holes are opened.
