How to Build Roof Gable End Cornice Returns

Measure the area from the end of the gable fascia to an area approximately 6 inches underneath the roof beam at each end of the roof using a tape measure.

Mark a piece of plywood in a triangular design to fit the area you measured in Step 1 using a framing square. The triangular wood becomes the cornice. Repeat for the other end of the roof.

Cut out the cornice pieces using a circular saw and straight-edge guide. You need two cornice pieces.

Test-fit the cornice pieces over the ends of gable on the roof. Install using finishing nails and a hammer into the ends of the beams driven up into the underside of the gable fascia.

Embed the heads of the nails below the surface of the wood using a nail set. Be careful not to split the cornice pieces.

Caulk the seams between the fascia boards and the cornice using silicone caulking and a caulking gun.

Finish the cornice returns by siding them according to the manufacturer's directions.