Building components · Frame Members
Beam
Explains the beam as the horizontal spanning member of a frame, distinct from joists and from the openings-head members it resembles.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a beam is
A beam spans between supports and carries whatever is applied along its length — a floor, a wall, other beams — delivering it to those supports as reactions at each end. It is the element that lets a building have space between its vertical supports.
Its behaviour is governed by bending and by how far it has to span, which is why a beam's size is far more sensitive to span than to the magnitude of the load it carries.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a floor joist. Joists are the repeated, closely spaced members that make up a floor; a beam is a heavier member that commonly carries joists.
- It is not a lintel. A lintel spans a specific opening in a wall and carries the wall above it; masonry lintels are published as a material entry.
- It is not a ground beam, which is the same idea in a different position with different exposure and a different relationship to the ground.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- beams
- primary beam
- spanning member
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- Its span, which dominates how it behaves far more than the loading does.
- What bears on it and where along its length, since a load near a support behaves differently from one at midspan.
- How it is supported at each end, including whether the support can accept the reaction.
- Whether it is restrained against sideways buckling along its length.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Beams deflect under load, and how much is acceptable depends on what they support — a finish that cracks is a different criterion from structural safety.
The reactions at a beam's ends have to be accepted by something, and support design is as much part of the beam's design as the beam itself.
Where a beam carries a floor above, its behaviour in fire is a design and regulatory matter rather than a property of the material alone.
Getting a beam into position, particularly in an existing building, is frequently the constraint that shapes how the work is done.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Junctions
Interfaces this element takes part in
Junctions where the condition between this element and another governs how the construction behaves. These name the junction and the subjects it raises; they are not details, arrangements or approved ways of building.
Beam End to Column
Where a beam meets a column, and where the connection's stiffness determines how the whole frame behaves.
Raises: Structural transfer · Fire continuity · Buildability · Movement
Where it is met
Application contexts
Building contexts where this element is commonly encountered. Association is not recommendation: appearing here does not mean the component suits every instance of that context, or any particular one.
- Intermediate Floor
- Superstructure
Related elements
Neighbouring components
Typed relationships to other elements. There is deliberately no generic “related” category: an edge that cannot be classified does not exist.
Narrower forms of this element
Clarifications
Commonly misunderstood
- That a beam's size follows from the load. Span usually dominates, which is why a longer opening needs a disproportionately larger beam.
- That any beam can replace a removed wall. What the wall was carrying, and where that load can go, has to be established first.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What is this beam carrying, and over what span?
- Where do the end reactions go, and can the supports accept them?
- What deflection is the design allowing, and does anything it supports depend on less?
- Is the beam restrained along its length, and does any proposed work change that?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- No span, section, deflection limit or capacity is stated here, and no beam can be sized from this entry.
- Removing a wall and installing a beam is structural alteration requiring qualified design and, commonly, regulatory approval.
Structural Frame Members
The columns, beams, joists, rafters, plates and bracing that make up a load-carrying frame, identified by the position each occupies.
Browse all frame members entries →