Q: How do I calculate the amount of siding needed for a house?
A: Siding is typically sold by the square foot, and lap siding coverage is determined by the siding’s exposure (the amount that will not be covered or “lapped” by other siding pieces). To figure the square footage of a house, total the sum of all the walls. To calculate a wall, divide it into rectangular and triangular sections. For the rectangles, multiply the width by the height (rounded to the nearest inch). For the triangular areas, multiply the base line (bottom) by the height (distance to peak), and divide by two. Add up the rectangles and triangles to get the wall’s total square footage. To ensure you have 10-15 percent of siding material for waste, don’t discount the area for windows and doors.