Mono-pitched roof

A mono-pitched roof is a single-sloping roof surface, often not attached to another roof surface. Mono-pitched roofs are sometimes called a pent roof, shed roof, lean-to roof, or skillion roof (in Australia). This is in contrast to a dual-pitched roof, also known as a gabled roof, which is pitched in two different directions.

A mono-pitched roof can also be a smaller addition to an existing roof, where keeping to the same slope (roof pitch) puts the mono-pitched roof lower than the ceiling height of the main structure. In this case even though the main roof has a flat ceiling, the mono-pitched part will have a sloping, or raked, ceiling line to maximise the ceiling height. The name lean-to roof comes from this form of addition.

Mono-pitched roofs can also be used to provide clerestory windows for a hallway or similar room where a row of windows is placed below the edge of the mono-pitched section reaching above the other roof below.

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Wikipedia