The content on this page is educational only. It is intended to help homeowners recognise common crack patterns, describe them more accurately and decide when to seek professional advice. It is not a diagnostic tool and does not assess, diagnose or rule out structural movement, settlement, subsidence, heave or any other defect.
No conclusions about the structural condition of any specific property should be drawn from this page. Cracks can arise from a wide range of causes, and accurate diagnosis depends on a physical inspection by an appropriately qualified professional with knowledge of the property, its construction, ground conditions and history.
Where there is any concern, or where cracks are visible, widening, recurring or accompanied by other signs such as sticking doors, sloping floors or movement at openings, a Chartered Building Surveyor or structural engineer should be instructed to inspect the property in person. The information on this page must not be relied upon as a substitute for that advice.
Before you do anything else, get a sense of three properties of the crack: its width, its pattern, and whether it is changing over time.
Hairline cracks (under ~1 mm) are extremely common in most plaster, render and brickwork. Cracks above ~3 mm warrant proper attention.
Vertical, horizontal, diagonal, stepped, tapered. Each pattern has typical underlying causes. The pattern matters more than the size.
A static crack is very different from a live one. Marking each end with a dated pencil note and re-checking in a few weeks tells you a lot.
The UK Crack Assessment Toolkit is the full PDF version of this awareness guide, with crack pattern diagrams and a monitoring template.
Diagrams, classification tables and a monitoring template you can use to track movement over time before bringing in a professional.
If you're buying a property and you've noticed cracking, the Survey Recommender will steer you towards the right RICS survey level.
Instruct a Chartered Building Surveyor or structural engineer in person where any of the following apply: cracks wider than 3 mm, cracks that are actively widening, cracks that pass through brickwork rather than just rendering, cracks accompanied by sticking doors or windows, sloping floors or visible movement at openings, or any crack appearing near a recently dug trench, a removed chimney breast or a property close to mature trees.