- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 26 Apr 2018
A girder is a large and deep type of beam that is used in construction. It is typically capable of longer spans and taking greater loads than a normal beam, and is often used as a main horizontal structural support for smaller beams, such as in bridge construction.
There are several different types of girder available depending on circumstances, and the load they are required to support:
- Smaller steel girders can be 'rolled' into the required shape. When girders become larger however, a standard rolled shape may not be available and a plate girder may have to be fabricated instead.
- A plate girder is typically an I-beam cross-section made up of separate structural steel plates which are welded, bolted or riveted together to form the deeper vertical web and narrower horizontal flanges of the beam. Plate girders are commonly-used for spans of up to 15m.
- A gantry girder is used for a gantry crane - typically consisting of two ‘A’ frames connected by a lattice cross member which straddles the work area. The lifting gear is suspended from the horizontal girder and can move along it on rails. For more information, see Types of crane.
- A box girder is fabricated from steel plates used to form a rectangular box. This resists torsion better than a plate girder and can be used when depth constraints mean a plate girder cannot be made deeper.
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
Their survival against the odds is a remarkable feature of the City’s history.
Immersed, charmed and inspired on conservation’s front line.
About JCT...and the rest
The Centre Building, London School of Economics
Architecture course essentials
Enhancing employee health and wellbeing
Underfloor heating opportunities as world radiator market cools.
Points to consider to make specifying sustainable.
It is not just about speed
The Flatiron Building, New York
Which way up should you lay a brick?