Can anyone give me a reasonable estimate for replacing a roof Per square , have both 1 & 2 story sf homes . Mostly 800 to 1100 sq ft . homes. I am looking to budget for replacement in Dayton Ohio. I believe that we can put new shingles over exhibiting shingles only if it will be a second set of shingles not a 3rd. How much to Re-shingle as well as to to remove old roof repair plywood and replace shingles.