By Joseph Lawson MEng (Hons), Director / Structural Engineer, Lawson Cook Limited
Cracks in walls, ceilings and brickwork are common in buildings and do not automatically mean that there is a serious structural problem.
Some cracks relate to normal drying shrinkage, thermal movement or minor historic settlement. Others can indicate movement within the structure, localised defects, foundation movement or problems with supporting elements such as lintels.
A structural crack survey is intended to assess the cracking in context and establish, as far as reasonably possible from the available evidence, what may be causing it, how significant it appears to be and whether further investigation or remedial work is required.
At Lawson Cook Limited, we regularly carry out structural surveys of properties where homeowners, purchasers, landlords or building surveyors have raised concerns about cracking or movement.
Before the Survey
Before attending site, it is helpful for the structural engineer to understand the background to the concern.
We will normally ask for:
The property address
Photographs of the cracking
Estate agent floor plans where available
Any building survey or mortgage valuation report
Previous structural reports, if applicable
Information regarding when the cracking was first noticed
Whether the cracking appears to be worsening
Details of recent building works or alterations
Any known drainage problems
Information regarding nearby trees or vegetation
This information can help us determine the appropriate scope of the survey before attending.
If the concern has arisen following a building survey, we generally recommend providing the relevant report so that we can understand exactly what has been raised.
What Does the Structural Engineer Look at?
A crack should rarely be considered in isolation.
During a structural crack survey, the engineer will normally assess the cracking alongside the wider construction and behaviour of the building.
Depending on the property and the nature of the concern, this may include looking at:
Internal wall cracking
External brickwork or masonry cracking
Cracking around windows and doors
Lintels and masonry above openings
Floors and ceilings
Junctions between extensions and the original building
Roof structure where accessible and relevant
Walls showing signs of leaning, bulging or distortion
Doors and windows that have become difficult to operate
Previous repairs or filled cracks
Nearby trees and vegetation
Visible drainage arrangements
Changes in ground level
Adjacent structures
Previous structural alterations
The purpose is to understand whether the crack forms part of a wider movement pattern.
Does the Engineer Measure the Cracks?
Yes, where appropriate.
Crack width can be useful information, particularly where several cracks are present or movement has been monitored over time.
However, crack width alone does not determine whether a crack is structurally significant.
The engineer will also consider:
Crack direction
Crack pattern
Position within the building
Whether it passes through structural materials
Whether it appears internally and externally
Whether there is associated distortion
The age and type of construction
Whether repairs have previously been carried out
Whether the cracking appears recent, historic or progressive
A narrow crack in an important structural location can sometimes be more relevant than a wider crack restricted to plaster.
What Do Different Crack Patterns Mean?
Different forms of cracking can suggest different mechanisms, although the appearance of a crack alone is rarely enough to confirm the cause.
Stepped Cracking
Stepped cracking through brickwork or blockwork follows the mortar joints and can sometimes be associated with differential movement.
Possible causes include:
Foundation movement
Seasonal ground movement
Nearby trees on shrinkable clay
Drainage problems
Localised settlement
Alterations to the building
The wider context of the property needs to be considered before reaching a conclusion.
Diagonal Cracking Around Openings
Cracking extending from the corners of windows and doors may relate to movement of the surrounding masonry.
It can also sometimes be associated with:
Defective or deteriorated lintels
Inadequate support above an opening
Thermal movement
Localised masonry movement
Previous alterations
Vertical Cracking
Vertical cracks can occur for various reasons, including shrinkage, movement between different materials or separation at the junction between parts of a building.
A common example is cracking between an extension and the original house.
Horizontal Cracking
Horizontal cracking may warrant closer attention where it is associated with wall movement, restraint problems, corrosion or other structural defects.
Again, the significance depends heavily on the construction and location.
What About Cracks in Plaster?
Plaster cracking is extremely common.
Fine cracks can occur due to:
Drying shrinkage
Thermal movement
Minor movement between materials
Changes in humidity
Normal movement within timber floors or roofs
The engineer will therefore consider whether the crack appears limited to the finish or whether there is evidence that the underlying masonry or structure has also moved.
Where necessary, localised opening-up may be recommended to confirm the underlying condition.
Will the Engineer Look Outside the Property?
Usually, yes.
External inspection can be extremely important because internal cracking may correspond with defects visible externally.
The engineer may look for:
Stepped cracking in brickwork
Distortion around openings
Cracked or displaced masonry
Previous repointing or repairs
Signs of movement at extensions
Condition of visible lintels
Movement to bay windows or other projections
Ground levels around the building
Nearby trees
Visible drains and manholes
Retaining walls or adjacent structures
A combination of internal and external observations often provides a much clearer picture than assessing the internal crack alone.
Are Trees Considered?
Where relevant, yes.
Trees can influence ground moisture conditions, particularly where buildings are founded on shrinkable clay soils.
The engineer may therefore consider:
Approximate tree size
Distance from the building
Species where known
Location relative to the cracking
Evidence of recent tree removal or pruning
However, the presence of a tree close to a building does not automatically mean that the tree is causing subsidence.
Ground conditions, foundation depth, drainage and the pattern of movement all need to be considered.
An arboricultural assessment may sometimes be recommended where vegetation appears relevant.
What About Drainage?
Drainage can also be relevant to structural movement.
Leaking drains can affect local ground conditions and may contribute to settlement in some circumstances.
If drainage is considered a possible factor, we may recommend a CCTV drainage survey or other specialist investigation.
Structural engineers do not normally inspect underground drainage during a visual crack survey unless this has specifically been included within the appointment.
Is the Survey Intrusive?
Normally, no.
Our structural surveys are generally visual and non-intrusive unless otherwise agreed.
This means we do not automatically:
Remove plaster
Lift floorboards
Excavate foundations
Open ceilings
Remove finishes
Expose concealed beams
Where important parts of the structure are concealed, we may recommend further investigation.
This could include opening-up works or trial holes carried out by others so that the construction can be inspected.
What Is a Trial Hole?
A trial hole is a small excavation used to establish information about an existing foundation.
This may help confirm:
Foundation depth
Foundation width
Foundation construction
Ground conditions immediately below the footing
Whether made ground is present
Trial holes can be particularly useful where foundation movement is suspected or where the existing foundation arrangement is important to the assessment.
They are not required for every cracking survey.
What Other Investigations Might Be Recommended?
If the cause of movement cannot reasonably be established from the initial survey, the engineer may recommend further investigation.
Depending on the circumstances, this could include:
Crack monitoring
Trial holes
CCTV drainage surveys
Ground investigation
Soil testing
Arboricultural advice
Opening-up works
Level surveys
Review of historic photographs
Review of previous structural reports
Investigation of concealed lintels or structural members
The investigation should be proportionate to the nature and severity of the defect.
Can One Survey Tell Whether the Building Is Still Moving?
Sometimes, but not always.
A site survey provides a snapshot of the building at a particular point in time.
The engineer may be able to form an opinion from the crack pattern, condition of repairs, distortion and other evidence as to whether the movement appears historic or potentially ongoing.
However, where this cannot be established with reasonable confidence, crack monitoring may be recommended.
Monitoring can help determine whether the cracks are continuing to change over a period of time.
What Happens After the Survey?
Following the site visit, a structural report can be prepared setting out the engineer's observations and professional opinion.
A typical Lawson Cook structural report may include:
Background
Why the survey was requested and any relevant information supplied by the client or building surveyor.
Property and Construction
A description of the relevant building construction and structural arrangement.
Site Observations
The cracking, movement or other defects observed during the inspection.
Structural Assessment
Our opinion regarding the likely mechanism and structural significance of the observed defects.
Further Investigations
Any additional investigations considered necessary before a definitive repair strategy can be established.
Recommendations
Practical recommendations for monitoring, repair, further investigation or structural works where appropriate.
Conclusion
A concise summary of the principal structural findings.
Where a precise cause cannot reasonably be established from the available information, the report should say so rather than providing an unsupported conclusion.
Will the Report Tell Me How to Repair the Cracks?
Where the cause is reasonably understood, the report may include recommendations for appropriate remedial works.
Depending on the defect, this could include:
Local masonry repairs
Repointing
Helical bar reinforcement
Lintel replacement
Local rebuilding
Timber repairs
Foundation strengthening
Drainage repairs
Monitoring before repairs are undertaken
In other situations, further investigation may need to be completed before an appropriate repair can be specified.
It is important to address the cause of movement, where possible, rather than simply filling the visible crack.
What If Subsidence Is Suspected?
Subsidence is one possible cause of cracking, but it should not be assumed simply because cracking is present.
An assessment may need to consider:
Ground conditions
Foundation construction
Trees
Drainage
Seasonal moisture changes
Historic alterations
Adjacent structures
Crack pattern
Building age
Evidence of progressive movement
Where significant foundation movement is suspected, a staged investigation is usually more appropriate than immediately recommending underpinning.
Further evidence may first be needed to establish the cause and extent of the movement.
Should I Have Cracking Inspected Before Buying a House?
If a building survey or mortgage valuation identifies potentially significant cracking, it can be sensible to obtain structural advice before completing the purchase.
This can help clarify:
Whether the cracking appears structurally significant
Whether further investigation is required
Whether significant remedial work may be necessary
Whether monitoring is appropriate
Whether the issue appears localised or more widespread
Where a mortgage lender has requested the structural report, it is also important to confirm whether they have any specific requirements regarding the qualifications or professional status of the person preparing it.
When Should You Arrange a Structural Crack Survey?
You should consider seeking structural advice where cracking is:
New or noticeably worsening
Diagonal or stepped through masonry
Visible both internally and externally
Associated with sticking doors or windows
Accompanied by sloping or distorted floors
Concentrated around a structural alteration
Associated with an extension separating from the original building
Affecting structural masonry rather than finishes alone
Identified as potentially significant within a building survey
Causing concern during the purchase or sale of a property
If you are uncertain whether a survey is necessary, photographs can often help us advise on the appropriate next step.
Structural Crack Surveys in Hertfordshire
Lawson Cook Limited is a structural engineering practice based in Hertford carrying out structural surveys and reporting throughout Hertfordshire and surrounding areas.
We regularly assess:
Cracking to houses
Suspected structural movement
Subsidence concerns
Cracking around windows and doors
Extension movement
Foundation-related defects
Lintel defects
Movement following alterations
Structural concerns raised within building surveys
If you are concerned about cracking, please send us:
The property address
Clear photographs of the cracking
Estate agent floor plans where available
Any relevant building survey
Details of when the cracking was first noticed
Any previous structural reports or investigations
We can then review the information and provide a quotation for the appropriate site survey and reporting.
Lawson Cook Limited
Structural Engineers
Hertford, Hertfordshire
info@lawsoncook.co.uk