Building On Rock
Based on the Soil Classification rock is considered one of the best surfaces to build a house foundation.
It comes under the Classification Class A.
That doesn’t mean its going to be cheap especially for a conventional raft or waffle pod slab.
Any excavation such as leveling the site and excavation for sewerage and drainage trenches is going to be be expensive. This is due to it requiring a heavy excavator and rock breaking equipment.
Keeping Costs Down
If you have a site that has rock close to the surface the most economic base construction is likely to be Piers for Lightweight Construction. (including Pole Houses and Queenslanders)
Also see Provisional Sums to find out the issues of finding rock during the construction.