Section

A section cuts a building with an imaginary vertical plane and draws what you see looking straight at the cut. Where the plan explains things horizontally, the section explains them vertically: floor-to-floor heights, slab and beam depths, how the stair climbs, how the foundation meets the ground, the shape of the roof and the level changes between spaces.

Where to cut

The section line is marked on the plan with a line and arrows showing the direction of view. It should pass through the part of the building that tells the most, so sections usually cut through stairs, double-height voids, wet areas or places where levels change. Sometimes one straight line is not enough and the cut steps to catch several key points.

Why sections matter

Much of how a room feels comes from its height. A double-height living room, a low entrance and a bedroom tucked into the roof can look almost identical in plan; the section shows the difference. Technically, sections are also where you check that structure, architecture and services do not clash vertically.

In visualization, the sectional perspective is a striking way to show inside and outside in one image. With cut surfaces in solid tone and the rooms behind lit and furnished, even non-architects quickly see how a building works.