A: The most important consideration in determining the cost of a new roof is the total area of the roof. If your roof has an area of three thousand square feet (which is about average for a medium sized house), the cost will be around $7000, which includes removing the old shingles and waterproofing roof penetrations such as chimneys and plumbing pipes. If your roof is particularly steep, or there is more than one layer of old shingles on the roof, add around $600 more for each of these considerations. Finally, fancy shingles with designer colors or added thickness can add a couple of thousand more to the total cost. But for an average house, $7000 is a good ball park figure.