Section Drawing
A vertical cut through the building that reveals what's stacked inside its walls and floors.
Quick Answer
A section drawing shows a vertical slice through a building along a cut line, revealing floor-to-floor heights, structural framing, wall assemblies, and how spaces stack on top of each other. Unlike a plan or elevation, it shows the building's interior structure and layered construction, not just its surface. Sections range from whole-building views to detailed wall sections at large scale.
The Full Picture
A section drawing exists because neither a floor plan (looking down) nor an elevation (looking straight at a face) can show what's happening vertically inside a building — how tall each floor actually is, what structure sits above a ceiling, or how a roof assembly is layered. A section solves that by slicing through the building along a defined cut line and drawing exactly what that cut exposes.
Mechanically, a building section cuts through the whole structure at a location noted on the floor plan, typically showing foundation to roof, with floor-to-floor heights dimensioned, structural elements (beams, slabs, foundations) visible, and major systems indicated. A wall section is a tighter, larger-scale cut through just one wall assembly, showing every layer — framing, insulation, sheathing, cladding, interior finish — stacked in true relationship to each other. Both types use the same cutting logic; they differ in scope and scale.
In practice, a section is where a lot of coordination questions get answered: whether there's enough ceiling plenum space for ductwork above a corridor, whether a stair actually clears the floor above at the height shown on the plan, or whether a roof parapet detail as drawn is even physically buildable. Estimators and superintendents reference sections constantly alongside plans to understand vertical relationships the plan alone hides.
Sections matter for constructability review and cost because they expose conflicts and assembly complexity that plans and elevations can miss entirely — a duct that needs more vertical space than the section shows is available, or a wall assembly with more layers (and more labor and material cost) than a simple plan line suggests.
Real Examples
Common Misconceptions
People assume: A section drawing and an elevation drawing show the same thing.
Actually: An elevation shows a wall's outer face, viewed straight on from outside the building. A section shows what's inside the building — cut open — revealing structure, layers, and floor heights an elevation never shows.
People assume: You only need a whole-building section, not wall sections.
Actually: A building section shows overall vertical relationships but is drawn too small in scale to show assembly detail. Wall sections, drawn much larger, are where the actual buildable assembly — insulation, waterproofing, framing — is specified. Both are needed for different purposes.
Does MeltPlan Solve This?
Partially — adjacentMeltPlan's Design Review reads section drawings as part of the full document set, checking that dimensions, assemblies, and heights shown are consistent with related plans, elevations, and details — flagging conflicts like insufficient clearances or mismatched call-outs. It doesn't perform structural or MEP engineering analysis of what a section shows.
Check sections against plans and details for conflicts →Frequently Asked Questions
What's the difference between a building section and a wall section?
A building section cuts through the whole structure to show overall floor heights and how spaces stack. A wall section is a tighter, larger-scale cut through one wall assembly, showing every material layer for construction detail. Building sections give the big picture; wall sections give buildable detail.
Where is a section cut taken from?
The cut location and direction are marked on the floor plan with a section symbol — a line with an arrow showing which way you're looking — so anyone reading the section can trace it back to exactly where on the plan it was taken.
Why are sections important for constructability review?
Because they're the drawing type that exposes vertical conflicts — insufficient space for ductwork, structure that doesn't clear a stair, an assembly that's more complex than the plan suggests — before those problems get discovered in the field.
Do sections show dimensions?
Yes — floor-to-floor heights, ceiling heights, and assembly layer thicknesses are typically dimensioned on a section, since vertical dimensions are exactly the information a plan or elevation can't convey.