A 'section drawing', 'section' or 'sectional drawing' shows a view of a structure as though it had been sliced in half or cut along another imaginary plane.
For buildings, this can be useful as it gives a view through the spaces and surrounding structures (typically across a vertical plane) that can reveal the relationships between the different parts of the buildings that might not be apparent on plan drawings. Plan drawings are in fact a type of section, but they cut through the building on a horizontal rather than vertical plane.
The direction of the plane through which the section is cut is often represented on plan drawings and elevations by a line of long and short dashes, called a section plane. If there are a number of sections, the line may have letters at each end indicating the name of the section drawing and an arrow showing the direction that the view takes.
The section line can take an indirect route through a building if this helps show the most important features or junctions in the building, as illustrated on the drawing below.
In this case, the section drawing would be named 'Section B-B'.
The scale of a section drawing will depend on the size of the building being drawn and the level of detail that needs to be shown. Sections may show the entire building, or may focus on a particular component, junction or assembly. In this case they can be similar to assembly drawings but differ in that they don’t usually include details of the actually assembly process.
Different types of cross hatching can be used to differentiate between different types of component on detailed sectional drawings. Standards exist for hatching that should be used on some common materials, for example, double diagonal lines indicate brickwork, a wave indicates insulation and so on.
Perspective sections include 3D projection of the spaces beyond the section plane and can be used to give a graphical illustration of the relationship between spaces and building components as well as their depths that can be very helpful in trying to interpret a complex design.
Increasingly, section drawings can be generated automatically by 3D modelling software, including perspective sections where required.
 Related articles on Designing Buildings Wiki
- As-built drawings and record drawings.
- Assembly drawing.
- Building information modelling.
- Component drawing.
- Computer aided design.
- Concept drawing.
- Design drawings.
- Detail drawing.
- Engineering drawing.
- General arrangement drawing.
- Installation drawings.
- Manual of Section - review.
- North American Paper Sizes
- Notation and symbols.
- Paper sizes.
- Production information.
- Scale drawing.
- Shop drawings.
- Site plan.
- Technical drawing.
- Types of drawings for building design.
- Working drawing.
 External references
- ‘Building Construction Handbook’ (6th ed.), CHUDLEY, R. and GREENO, R., Butterworth-Heinemann (2007)
Featured articles and news
Read about RSHP's British Museum extension which has been shortlisted for the 2017 Stirling Prize.
Read our introductory article to building a house extension.
More updates from DCMS about the large-scale testing of cladding systems and the number of buildings affected.
UandI secure resolution to grant planning consent for major new regeneration project.
IHBC article considers how heritage is dealt with when infrastructure schemes are authorised.
It was the tallest structure in the world for 3,800 years, but to this day the exact construction techniques are a mystery.
Shortlist for the industry's most coveted award announced.
Government responds to Mark Farmer's review of industry, rejecting the call for a levy on clients.
Peter Hansford to examine what wider lessons can be learned from the fire.
Every project is subject to uncertainty. How can construction better understand uncertainty for performance improvement?
MAD Architects reveal their designs for a futuristic campus for electric car manufacturer.
Homebuyers could borrow more with better forecasting of energy bills, according to industry consortium's new report.
Read our introductory article on carbon capture and storage.