[QUOTE="Mattax
I'm telling you need to talk to a crew that knows the material and isn't afraid of it. Then you won't have to buy any new material, just the labor and the repairs. It still won't be cheap, but its very unusual for roof that still has that much unbroken shingles to be cheaper to replace. With slate the rule of thumb is somewhere around 30% damaged. Terra cotta is a little different but that gives you a general idea of what someone in the field would be using as the typical tipping point.