A hip roof is a popular design that slopes down from a ridge line to all exterior wall planes. It features a consistent perimeter eave or overhang that helps protect the wall surfaces, as well as provide an increased element of shade. An accurate estimate of roofing materials for a hip roof requires calculating the surface area. It is a matter of dividing it into its geometric shapes and applying a basic mathematical formula.
Measure the overall horizontal length of the eave for the section of the roof area being calculated. Record this measurement as dimension A.
Measure the distance from the eave edge to the centre of the ridge line, perpendicular to the eave. Record this measurement as dimension B.
Calculate the area of the roof section measured in steps 1 and 2 by multiplying dimension 'A' times dimension 'B' to define the square footage of the roof section.
Repeat Steps 1 through 3 for each individual section of roof, then add the totals together to get the overall roof area.
Roofing materials are sold by both the square footage and "squares," or 100-square feet. To determine the number of squares for the roof, divide the overall total square footage by 100.