Building components · Terminations
Movement Joint
Explains the movement joint as a designed break, and why its position is determined by movement rather than by convenience.
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 movement joint is
Materials change size with temperature and with moisture, and different materials do it by different amounts and sometimes in opposite directions. A movement joint is a deliberate break that lets that happen without the material being forced to crack in a place nobody chose.
The word covers several distinct cases: joints that allow expansion, joints that control where shrinkage cracks form, and joints that separate two elements expected to move independently. What they share is that the discontinuity is designed rather than accidental.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a construction joint. A construction joint is where work stopped and restarted and is intended to act as continuous; a movement joint is intended to move.
- It is not a crack. A crack is where movement occurred without provision; a joint is where it was provided for.
- It is not a sealant. Sealant closes a movement joint against weather; the joint is the gap and the sealant is one component within it.
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.
- movement joints
- expansion joint
- control joint
- contraction joint
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- Being positioned where movement actually concentrates, which follows from the materials and the geometry rather than from convenience.
- Passing through everything that needs to move, since a joint interrupted by a rigid finish is not a joint.
- The material closing it being able to accommodate the movement repeatedly over its life.
- Not being bridged later by mortar, render, tiling or a rigid fixing.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Different materials move by different amounts and in different directions with moisture — clay units tend to expand over time while concrete units shrink — so joint provision is material-specific.
A joint through an external wall is a hole through it, and closing it against weather while letting it move is exactly the difficulty.
Joint sealants have a finite life and are among the components most likely to need replacing during a building's life.
A joint that is bridged by a rigid finish applied over it has been eliminated, and the crack will simply appear elsewhere.
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.
Materials
Commonly incorporates
Materials this element commonly contains as a distinct constituent part, rather than being made of.
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.
Movement Joint Through a Surface
Where a movement joint in the construction must be carried through the finish above it, rather than being covered over.
Raises: Movement · Moisture · Weathering · Buildability
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.
- Basement
- Boundary Structure
- Building Envelope
- Deck & Terrace
- External Wall
- External Works
- Flat Roof
- Hardstanding
- Internal Partition
- Wet Area
Clarifications
Commonly misunderstood
- That movement joints are unsightly compromises. They put the discontinuity where it was chosen rather than where the material decides.
- That a joint can be moved to a tidier position. Its position follows from where movement concentrates.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- Where are the movement joints in this construction, and what determined their positions?
- Does each joint pass through every layer that needs to move?
- What closes the joint, and what is its expected life?
- Has any subsequent finish bridged a joint?
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 joint spacing, width, sealant type or movement allowance is stated here.
- Movement joint provision is a design calculation based on the materials, geometry and exposure of the specific construction.
Terminations & Weathering
The elements where a plane stops, turns up, sheds water or is deliberately interrupted — parapets, upstands, flashings, drips, weeps and movement joints.
Browse all terminations entries →