A home often develops internal wall cracks at some point, and it can be challenging to determine whether they are seeing a minor, cosmetic crack or the early stages of subsidence. If a crack caused by subsidence is left unattended, it can quickly worsen and continue to grow, leading to further issues; it is therefore vital to identify it as soon as possible and to contact a specialist such as Subsidence Ltd. In this post, we explain how to recognise wall cracks that are unlikely to be home subsidence‑related and highlight the most common types that generally do not require intervention.
Why Cracks in Your Home Aren’t Always a Sign of Subsidence
Many people might notice cracks in their home, such as hairline settlement lines, small thermal splits, or slight plaster shrinkage, which can be concerning. These cracks can sometimes appear suddenly or run across a freshly painted wall, and this might alarm homeowners that subsidence is present in their property. However, if you think that the crack in a wall is due to subsidence, it’s important to contact a team of professionals like Subsidence Ltd to take a look.
The British Research Establishment has listed damage categories with descriptions of typical damage as a guide on when cracks need action.
| Category | Crack Size | Description | Subsidence Ltd Advice on action needed |
| 0 | 0.1mm | Hairline cracks of less than about 0.1 mm which are classed as negligible | We would advise to carry out cosmetic repairs or speak to a local builder/decorator to carry them out for you. |
| 1 | <1mm | Fine cracks that can be treated easily using normal decoration. Damage generally restricted to internal wall finishes; cracks rarely visible in external brickwork. | We would advise to carry out cosmetic repairs or speak to a local builder/decorator to carry them out for you. If you are starting to see cracking externally then monitor this. |
| 2 | <5mm | Cracks easily filled. Recurrent cracks can be masked by suitable linings. Cracks not necessarily visible externally; some external repointing may be required to ensure weather-tightness. Doors and windows may stick slightly and require easing and adjusting | We would advise that you contact us and we will triage your property to advise you on next steps. |
| 3 | 5-15mm | Cracks that require some opening up and can be patched by a mason. Repointing of external brickwork and possibly a small amount of brickwork to be replaced. Doors and windows sticking. Service pipes may fracture. Weather-tightness often impaired | We would advise that you contact us and we will triage your property to advise you on next steps. |
| 4 | 15-25mm | Extensive damage which requires breaking-out and replacing sections of walls, especially over doors and windows. Windows and door frames distorted, floor sloping noticeably. Walls leaning or bulging noticeably, some loss of bearing in beams. Service pipes disrupted. | We would advise that you contact us and we will triage your property to advise you on next steps. |
| 5 | >25mm | Structural damage that requires a major repair job, involving partial or complete rebuilding. Beams lose bearing, walls lean badly and require shoring. Windows broken with distortion. Danger of instability. | We would advise that you contact us and we will triage your property to advise you on next steps. |
Types of Cracks that are Unlikely to Indicate Home Subsidence
– Settlement Cracks
Often, newly constructed or renovated homes develop settlement cracks as fresh materials compress and the structure adjusts to its own weight. These fine lines are slim, usually vertical fissures that appear where walls meet ceilings or around window reveals. Once the settling stops, these cracks usually stabilise and only need filling and repainting; so it’s good to just monitor them and ensure they don’t worsen further.
– Cracks in Plaster
Internal plaster can crack or split as it dries, reacts to humidity changes, or rests on timber studs that flex with temperature. This process leaves fine crazing or small splits on the surface, while the brick or blockwork behind stays firm. Because the underlying structure remains unaffected, these cosmetic cracks can be remedied with filler and a fresh coat of paint.
– Cracks Less than 2mm Wide
Hairline openings under two millimetres wide usually reflect minor shrinkage or settlement rather than true foundation movement. If narrower than the edge of a £1 coin, they rarely affect load‑bearing elements. Such cracks tend to remain static after forming and can generally be concealed with flexible filler, so they do not warrant structural investigation or contacting a subsidence specialist in most domestic cases.
– Cracks that do not Widen
When a crack shows no measurable change over several seasons, it suggests that the movement which created it has ceased. The initial shift may have resulted from drying shrinkage, thermal cycling, or slight timber movement. Because the gap is static, the foundation is considered stable and the ground below firm, so no further intervention or subsidence assessment is normally necessary.
– No Lintels on Windows
Many older properties rely on brick arches rather than steel or concrete lintels above window and door openings. Minor stepped cracks may appear as the arch settles under load, radiating from the opening due to localised bearing stresses. Installing a modern lintel redistributes the load and resolves the issue without disturbing the foundations, because the cracking is not the result of subsidence.
– Thermal Cracks
Different building materials expand and contract at varying rates as temperatures fluctuate, producing vertical or horizontal fissures known as thermal cracks. Because the movement is cyclical and generally uniform across the structure, the load path stays intact and the foundations remain unaffected by subsidence. When the temperature stabilises, the gaps close or reduce, leaving the building sound and requiring only cosmetic repair.
Contact Subsidence Ltd
If you notice cracks in your house that suggest subsidence, contact Subsidence Ltd. Our resin‑injection system can raise, re‑level and re‑support your home in as little as a day, avoiding the disruption of underpinning. With over 16 years of experience providing home subsidence repairs and a highly professional and skilled team, trust us to fix any subsidence issues. Use our online subsidence postcode checker to assess the subsidence risk, and our repair‑cost tool to estimate likely expenses. For a free, no‑obligation quote, complete our online contact form or call us on 0333 130 0592 for help with subsidence problems.
CEO of Subsidence Ltd
