How and Why Cracks Form in Buildings
Cracks often form as buildings respond to natural changes in temperature, moisture, and load. As materials expand and contract, small fissures can appear in plaster, mortar, or brickwork. These are often superficial and part of normal building behaviour. Older buildings are especially prone to this, simply because materials have been moving and adjusting for decades.
Some cracks appear due to drying shrinkage in plaster or timber. Others arise from the settlement that occurs when a building first beds onto its foundations. In many cases, these cracks do not progress and are not a sign of structural failure.
However, some cracks require closer attention. Cracks caused by structural movement tend to follow patterns. They may widen with height, run diagonally, or pass through multiple materials. Movement caused by subsidence or heave can create stepped cracks in brickwork, often seen around openings such as windows and doors. Understanding how the building is behaving is essential before drawing conclusions.
Assessing the Significance of a Crack
A surveyor considers several factors when assessing whether a crack is serious. The location of the crack is important, as cracks near load-bearing elements or foundations may carry more significance than hairline cracks in plaster. The width and depth also matter. A long but thin crack may be less concerning than a shorter, wider one that suggests recent or ongoing movement.
Surveyors also consider the age and construction of the building. Timber frame properties behave differently from solid masonry structures. Properties built on shrinkable clay soils may move seasonally, creating recurring patterns of cracking. Homes that have undergone alterations, such as extensions or loft conversions, may also show cracks where old and new structures meet.
The history of the cracking is another key factor. A crack that has remained unchanged for years is unlikely to pose a threat. A crack that widens over time, however, may indicate active movement. Monitoring can therefore be essential in determining whether the building is stable.
What Cracks Can Reveal About Underlying Issues
Cracks can provide valuable clues about what is happening within the structure. Vertical cracks may relate to differential settlement. Diagonal cracks can indicate foundation movement or thermal stress. Cracks radiating from corners of openings often signal that the surrounding materials are under tension.
If cracks appear alongside sticking doors or windows, sloping floors, or rippling in wallpaper, the issue may be more significant. These signs suggest that movement is occurring across the structure, not just in a single material.
Moisture is another contributing factor. Damp walls may crack as the material dries unevenly. Salts can crystallise beneath paint or plaster, pushing the surface away and creating fissures. Without addressing the cause of the moisture, the cracks will continue to appear even after repairs.
How Surveyors Investigate Cracking
A thorough investigation begins with observation. Surveyors examine the crack’s pattern, location, width, and direction. They look for related signs of movement elsewhere in the building. This helps form a picture of whether the crack is isolated or part of a wider issue.
Surveyors then consider the surrounding environment. Soil type, tree proximity, drainage conditions, and weather patterns can all influence movement. For example, shrinkable clay can contract significantly during dry spells, creating seasonal cracking. Conversely, excess groundwater may soften the soil beneath foundations and lead to downward movement.
In some cases, further investigation is needed. Monitoring may be recommended to track whether cracks are widening. This helps determine whether the building has stabilised or whether intervention is required. Only after understanding the root cause can a surveyor recommend theappropriate course of action.
Repairing Cracks the Right Way
Repairing cracks without understanding their cause is rarely effective. Filling a crack may hide the problem temporarily, but if movement is ongoing, the crack will reappear. The correct repair depends entirely on what caused the cracking.
Cosmetic cracks caused by shrinkage or minor settlement can often be repaired easily once the movement has ceased. Structural cracks may require strengthening measures such as stitching, foundation improvement, or localised rebuilding. Moisture-related cracks will need damp issues addressed before any successful repair can take place.
Surveyors guide homeowners to the right solution by identifying the source of the problem. This ensures repairs are not only effective but also long lasting.
Conclusion
Cracks in buildings are common and often harmless, but they should never be ignored without understanding their cause. A crack is a symptom, not a diagnosis. Only by assessing the context, construction, and behaviour of the building can you determine whether a crack is a cosmetic nuisance or an indicator of something more serious.
If you have concerns about cracks in your property, a professional survey provides clarity and reassurance. At Harrison Clarke, we offer informed, practical advice to help you understand what your building is telling you and what steps, if any, you need to take.
For more expert advice on surveying and property matters, check out our range of informative videos on our website or YouTube channel. Harrison Clarke Chartered Surveyors is here to guide you every step of the way!
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