Roof area calculator Cross Hipped

A cross hipped roof is an L-shaped hip roof: both wings slope down on every side and end in triangular hips. It looks like two hip roofs joined at a corner, with a valley on the inside of the L.

What you need to measure

• L1 and L2: the outside lengths of the two wings.
• l1: the width of the wings.
• C1 and C2: the lengths of the two ridges, measured from the corner where they meet.
• H: the rise of the ridges above the eaves.

How the area is calculated

The long sides of the wings are trapezoids with the rafter √((l1 / 2)² + H²) as height. Each wing ends in a triangular hip whose size depends on how far its ridge stops from the end.

The calculator adds the four trapezoids and the two hip triangles, and shows the pitch of the hips separately when they differ from the main slopes.

Worked example

1. L1 = 12 m, L2 = 10 m, l1 = 6 m, C1 = 6 m, C2 = 4 m, H = 3 m.
2. Each ridge stops 3 m from the end of its wing, so the hips have the same 45 degree pitch as the long sides.
3. Floor area = 96 m², rafter = 4.24 m, run = 3 m.
4. Roof area = 96 × 4.24 / 3 = 135.76 m², the same as the cross gabled version.

Tips before you order materials

• Count hips and valleys separately: hips need hip caps, valleys need flashing.
• This shape has the most cuts of the L roofs: plan 15% extra material.

Frequently asked questions

Is a hipped L roof more expensive than a gabled one?

The surface is about the same for the same pitch, but hips add ridge caps, labour and waste, so the total cost is usually higher.