Cracking in a property can be worrying, but it does not automatically mean there is a serious structural problem.
Buildings move over time as they respond to changes in temperature, moisture, loading, alterations and ground conditions. The important point is to understand where the cracking is, how wide it is, what pattern it follows and whether it is changing.
At Stokemont, our Surveyors regularly inspect cracking as part of Defect Analysis Reports, helping property owners understand the likely cause and what should happen next.
How Serious Is a Crack?
BRE Digest 251 provides a useful guide to the significance of cracking in low-rise buildings.
In broad terms:
- hairline cracking below 0.1mm is negligible;
- cracks up to 1mm are very slight;
- cracks up to 5mm are generally classed as slight;
- cracks between 5mm and 15mm, or several cracks of around 3mm, can fall within a moderate category;
- wider cracking may indicate more significant movement.
Crack width is only part of the picture. The number, location, direction and progression of cracks are equally important.
Several smaller cracks following a consistent pattern can sometimes be more significant than one isolated crack.
Why Do Cracks Appear Around Windows and Doors?
Cracks often develop around windows, doors and archways because these openings interrupt the continuity of a masonry wall.
Loads are redistributed around the opening, creating natural stress concentrations at the corners.
This can result in diagonal, stepped or hairline cracking, particularly where masonry, plaster, lintels and window frames meet.
This type of cracking is common and does not automatically indicate serious structural movement.
Older Buildings, Foundations and Movement
Older properties are often built on comparatively shallow foundations.
These can be more responsive to changes in ground conditions, particularly where soil moisture varies throughout the year.
Extensions and later alterations can also move differently from the original building, particularly where foundation depths, materials and construction methods differ.
This is why cracking often appears at junctions between original and later construction.
Trees and Vegetation
Mature trees, shrubs and hedging can influence ground conditions, particularly where shrinkable clay soils are present.
Vegetation draws moisture from the soil, and during prolonged dry periods this can contribute to localised shrinkage.
The extent of any influence will depend on factors such as:
- species and size;
- distance from the building;
- root spread;
- foundation depth; and
- underlying soil conditions.
The presence of vegetation does not automatically mean it is causing the cracking, but it should form part of the wider assessment.
Retaining walls and hard landscaping may also influence the direction of root growth and can therefore be relevant in some cases.
Drainage Should Also Be Considered
Defective drainage can sometimes contribute to movement by affecting the ground supporting the foundations.
Where cracking is being investigated, accessible drains should therefore be checked where appropriate.
If the drainage is clear and free-flowing, this can help rule out one possible cause.
Why Monitoring Matters
Where cracking is more widespread, several millimetres in width or follows a consistent structural pattern, monitoring is often the sensible next step.
Crack-monitoring gauges or tell-tales can be used to establish whether the movement is:
- stable;
- seasonal; or
- progressive.
This is important because repairing the visible crack before the movement has stabilised can simply result in it reopening.
When Should Repairs Be Carried Out?
If monitoring confirms that movement is stable, conventional repairs may be sufficient.
These can include plaster repairs, redecoration, localised repointing, render repairs and replacement of cracked finishes.
If movement is continuing, further investigation should take place before permanent repairs are undertaken.
In some cases, localised masonry reinforcement, such as helical bars, may be appropriate once the underlying cause has been addressed.
Should Trees Be Removed?
Not necessarily. Wholesale removal of mature vegetation is not always the right first response, particularly where shrinkable soils are present.
Controlled reduction and ongoing management may be more appropriate, subject to arboricultural advice.
When Should You Notify Your Insurer?
Where cracking is extensive, appears to be progressing or raises concern about possible subsidence or ground movement, it may be appropriate to notify the buildings insurer.
The insurer may choose to arrange monitoring, appoint specialist advisers or undertake further investigation before deciding on the appropriate repair strategy.
When Should You Instruct a Defect Analysis Report?
If cracking has appeared and you are unsure what it means, a targeted Defect Analysis Report can help establish:
- the likely cause;
- the significance of the cracking;
- whether monitoring is required;
- whether further investigation is necessary; and
- the appropriate next steps.
At Stokemont, our Surveyors undertake Defect Analysis inspections across London and the surrounding areas.
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The key is to understand the cause before carrying out repairs. In many cases, cracking can be managed relatively simply once it has been established whether the movement is stable, seasonal or progressive.
