Rock/Ledge found during site work

[Benjamin K.]

I'm looking at building on a site that likely has a lot of ledge/rock. From what I've seen, many contractors have a generic "there will be an extra charge" for rock/ledge removal. 

Do most people push to have figured (hourly rate, per cubic yard of rock removed, etc.) added to the contract or is that wishful thinking? What is the "common" way this is addressed in most contracts? Experience with blasting vs. hammering it out, etc?

Thanks!

Ben