Joe,
Costs for roofing are measured in squares (10' x 10'). When comparing estimates, my advice is to compare apples-to-apples - the exact same thing from each contractor.
Also, I strongly advise you to have ALL roofing materials changed on a rehab job (vent boots, drip edges, chimney crickets, etc.) b/c if you DON'T, when there is leak, that leak will be b/c of "YOOOOOUR old roofing materials that you made me leave on, not with MYYYYYYYYY new shingles" - don't be "penny wise and pound foolish".
Most builders are paying in the $115 - 155/square price range for complete roofing jobs. Their costs are slightly lower than rehabbers b/c 1) there is significantly less trash to haul off on new construction and 2) they do high enough volume to obtain deep discounts on labor and materials.
Finally, know that roofing costs are effected by external influences. If you are looking for roofing materials in the Winter, many times costs are lower than in the heat of the Summer. Also, roofing costs skyrocket immediately following weather events (tornados, hurricanes, HAIL, etc.). Roofing materials costs can also be severely impacted by external costs, the most significant of these being the price of fuel for transportation, natural gas for the manufacturing and electricity production processes, and crude oil for the material itself.
Hope this helps.
-Greg Wilson
The REI Mentor
