Edges where two planes meet
Ridge: a level line at the top where two planes slope down in opposite directions. Hip: a sloped external corner where two planes both slope down and away from the line, typical of hip roofs. Valley: a sloped internal corner where two planes slope down toward the line and water collects.
Hips and valleys can look similar from above. Ask which way water runs: away from a hip, into a valley.
Edges with roof on one side only
Eave: the lower, roughly level edge where water runs off, usually with a gutter. Rake: the sloped edge at a gable end, running from eave to ridge.
Walls that meet a roof, such as a second story above a porch, are not eaves or rakes. They are flashing conditions (step or headwall flashing) and should be measured on their own.
Which materials follow which edges
Drip edge is commonly measured along eaves and rakes. Starter strip is commonly measured along eaves, and along rakes when the manufacturer calls for it. Ridge cap is measured along ridges and hips. Valley lining or metal follows valley length.
Eave and valley lengths also matter where ice-barrier underlayment is required. Requirements differ by jurisdiction and product, so confirm with the local building department and the manufacturer instructions.
Reading edges in a RoofSnap report
RoofSnap classifies edges from the planes on either side using pitch, direction and adjacency, and colors them by type on the diagram. Totals are listed for eaves, rakes, ridges, hips and valleys.
Internal lines depend on available elevation data. If only an outline is shown, the roof may still have hips or valleys. Check the satellite view before relying on a zero total.
Sources & further reading
Product details reflect RoofSnap’s current measurement and report workflow. Geometry examples are rounded illustrations, not measurements of the pictured property.
Google Solar API documentation