The Double Hip Roof Area calculator computes the surface area of a hip roof with a hip roof dormer based on the dimensions.
INSTRUCTIONS: Choose units and enter the following:
Hip Roof Area (sA): The calculator returns the total surface area in square feet (ft2). However, this can be automatically converted to compatible units via the pull-down menu. If DETAILS are chosen, the calculator also returns the following:
A hip roof is basically a rectangular trapezoid volume has regular trapezoids in the front and back and triangles on the sides. The bottom and top rectangles are centered, form parallel planes and separated by the height. The complication of the hip roof dormer introduces the intersection geometries. All of the lines have to be computed based on the specified lengths and pitch angles. Fortunately, trigonometry wins!
The total surface area is the area of the main hip roof plus the dormer sides (tan) and end (green), minus the end of the dormer that covers part of the main hip roof (red).