Replacing the entire roof at once may also be best for a consistent appearance and for prolonging its stability. Estimating the size of your roof can be a headache if you don’t have the original blueprints.(Image: https://artisanqualityroofing.com/wp-content/uploads/2019/04/Roof-replacement-costs-diagram-1000px.png) The slope and shape of your roof—hipped, gabled or flat, for example—dictate the number of shingles, shakes or tiles you’ll need.(Image: https://s3-media0.fl.yelpcdn.com/projectphoto/HpOrYoZ7811uXlRMqRlrhw/l.jpg)