A section is a drawing that shows a building cut through vertically. It reveals what is inside: floor heights, ceiling heights, structural systems, stairs, and the relationship between interior spaces. It is one of the most useful drawings in architecture because it shows things plans and elevations cannot.

Sections are drawn as if the building were sliced and the near half removed. The cut surfaces are shown with heavy lines. What is beyond the cut is shown in elevation. Hatching indicates materials like concrete, masonry, or insulation.

Different sections serve different purposes. A building section cuts through the entire building, showing how floors stack and how the roof meets the walls. A wall section zooms in on a specific part of the construction, showing layers of materials and how they connect. A detail section shows a single junction at a large scale.

Sections are essential for understanding how a building works. They show the vertical dimension that plans flatten. A building that looks good in plan and elevation can still fail in section if the ceiling heights are wrong or the structure blocks the space.