Approximately how many squares of asphalt shingles are to be ordered for the rear of the house, allowing 10% for starter and waste with a slope multiplier factor of 1.3?

• A. 14 squares
• B. 17 squares
• C. 19 squares
• D. 21 squares

Answer: (B)

To determine the number of squares of asphalt shingles needed for the rear of the house while considering waste and slope, it's crucial to understand how the calculations work.

When calculating the total number of squares required for roofing, the first step is to take the total area that needs to be covered. Then, the area calculated is multiplied by the slope multiplier—this accounts for the increased surface area due to the pitch of the roof.

After determining the adjusted area with the slope multiplier, it's standard practice to add a percentage for starter strips and waste material. In this case, 10% of the total area is added for this purpose. This means you multiply the adjusted area by 1.1 (which accounts for the original area plus the 10% extra).

To arrive at the final number of squares, you divide the total area by the square footage covered per square of shingles. A square typically covers 100 square feet. By following these calculation steps with the provided values, arriving at the figure of 17 squares signifies that after all adjustments for slope and waste, this number accurately reflects the materials needed to complete the roofing project without running short.

This careful approach ensures that homeowners can confidently order the right amount of shingles, eliminating the risk of excess material