This video is about Pitched or sloped roofs which are ancient. The first were likely made of thatch.
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They were pitched to drain water and thick to provide insulation. In contrast, the flat roof is historically an arid climate phenomenon, where rain and subsequent drainage is less an issue. From the parthenon to 550 madison ave the gable roof is ubiquitous. Variations are the hipped roof, seen on buildings like Palladian Villa’s, or the simple cottage home. On this roof all four sides pitch toward a central point like a pyramid. The mansard roof was became popular in France and is commonly seen in the victorian era. And the gambrel roof, with four planes and two distinct pitches is likely to be seen on Barns across America. Modern architecture, more often than not features flat roofs for their simplicity. While traditional architecture is associated with the pitched roofs of centuries gone by.
The Romans used openings in a roof as a way to keep a building cool and provide light. They did so with an oculus at the Pantheon in Rome which also happened make the roof lighter and thus more structurally sound. Architects and builders have taken this idea further throughout history with roof objects like the dormer. A dormers ad functional space below the roof or provides ventilation to a space that needs it. In the case of a dormer the roof is lifted and a window or louver is added. Dormers can utilize simple gable or shed roofs or become more decorative as is the case with the eyebrow dormer. The cupola is a structure that sits on top of a roof or dome. It’s purpose is also to add light or ventilation to a space. A cupola can also be made to accommodate a bell, known as a belfry. Or, it can accommodate a light fixture in which case it’s called a lantern. Finally it can be made large enough to be occupied in order for the user to enjoy the weather or a view. This is known as a belvedere.
So how do people get to the roof? Before the elevator stairs and structural systems were large considerations in building height. And up until the mid 19th century, and the advent of the safety elevator, people literally climbed to the top of buildings. The dichotomy the stair presents is that while it makes buildings more than one story possible it also limits their height. So to access the lofty spaces created by designers stairs come in lots of shapes and sizes. They can be straight run, winding, switchback, curved, and spiral. And today the stair still serves as an architectural element, a point of interest and an alternative means of egress when the power goes out. The most important thing about a stair is that it’s comfortable to use. That is the length of the tread together with the height of the riser must accommodate an average persons gate.