Hip Roof Layout and Tile Quantity
A hip roof is 32 ft wide at the eave and 24 ft deep in plan, with a 6/12 slope and 12-in. eave overhang on all sides. The specified tile is a flat concrete tile 18 in. long and 12 in. wide with a 9-in. exposure and 3-in. headlap. The supplier delivered 1,150 tiles, and the contractor plans to start the field at the left rake with full tiles, letting cut tiles fall at the right hip and valley. The roof has two valleys and four hips. The owner wants the hip lines to look balanced, and the local wind zone requires fastening every tile at the head with two nails. The contractor has not added waste or hip and ridge tiles to the order, and the job is scheduled to start in three days.
1. Calculate the approximate number of field tiles required and evaluate whether 1,150 tiles is enough.
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Roof plan area = 32 ft x 24 ft = 768 ft². The slope factor for 6/12 is the square root of 1 plus (6/12)², which is 1.118. Actual roof area = 768 x 1.118, or about 859 ft². One tile covers 12 in. x 9 in. exposure = 1.0 ft x 0.75 ft = 0.75 ft². Field tiles = 859 divided by 0.75, or about 1,145 tiles. That is before waste, hip and ridge, valley cuts, and breakage. A normal waste allowance of 5-10% adds 57-115 tiles, and hip and ridge tiles are separate. Therefore 1,150 is only about the theoretical field count and is not enough for the job. The contractor must order additional tile plus hip and ridge pieces, and verify the actual exposure against the manufacturer's instructions.
2. Is starting at the left rake with full tiles the right layout approach? Explain how to lay out hips, valleys, and fastening.
Read the worked answer
No. Starting full tiles at one rake pushes all the cut work to the opposite hip and can produce a wide, visibly unbalanced cut at the hip and misaligned courses. For a hip roof, establish control lines from the centerline or from the ridge and hip intersections so cuts are balanced on both sides; snap chalk lines for course exposure and check the diagonal hips for straightness. Lay field tiles from a control line, not from the rake. At hips and valleys, cut tiles to fit and keep the cut edges parallel to the hip or valley line with a consistent gap. In the wind zone, fasten every tile with two nails at the head as required; place nails so they are covered by the next course and do not pierce flashing. Dry-lay a section to confirm exposure and cuts before nailing. Also order hip and ridge tiles separately.