MET SURVEYORS
Expert Advice on Property Matters
Subsidence Survey London
Concerned About Cracks, Movement or Possible Subsidence?
Cracks appearing in a property can be worrying, particularly when they appear suddenly, become wider or are accompanied by other signs of movement.
While cracking can sometimes be associated with subsidence, there are many other possible causes. Settlement, thermal movement, drainage problems, alterations, extensions and differences in construction can all result in cracking.
If you are concerned that your property may be suffering from subsidence or structural movement, Met Surveyors can assess the circumstances and advise on the appropriate type of survey or investigation.
Where there are significant signs of movement or a wider concern about the structure of the property, a Structural Survey may be appropriate.
Where you have one particular structural concern, such as a crack to one wall or movement where an extension meets the original house, our Specific Issue Survey may be more suitable as a starting point.
What Is Subsidence?
Subsidence occurs when the ground supporting part of a building moves downwards.
If movement in the ground is sufficient, the foundations may move with it and this can result in cracking or distortion to the structure above.
London and parts of the South East contain extensive areas of clay soil. Clay can shrink when it loses moisture during prolonged periods of dry weather and expand again when moisture levels increase.
However, ground conditions are only one possible factor.
Structural movement can also be associated with:
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Trees and large vegetation
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Damaged or leaking underground drains
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Inadequate or shallow foundations
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Poorly constructed extensions
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Historic alterations
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Changes to surrounding ground conditions
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Different foundation types within the same property
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Previous structural movement
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Localised building defects
The presence of cracks alone therefore does not establish that a property is suffering from subsidence.
What Are the Signs of Possible Subsidence?
There is no single sign that conclusively proves that a building has subsidence.
However, movement may warrant further investigation where you notice issues such as:
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New diagonal cracks around doors or windows
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Cracks becoming noticeably wider
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Cracking visible both internally and externally
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Cracks that are wider at one end than the other
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Previously repaired cracks opening again
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Doors or windows suddenly becoming difficult to open
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Gaps appearing around window or door frames
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Distortion to walls or openings
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Movement between an extension and the original property
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Uneven or locally distorted floors
The position, pattern and extent of movement all need to be considered alongside the age and construction of the property.
Not Every Crack Means Subsidence
This is particularly important.
Cracks are common in buildings and can occur for many reasons that have nothing to do with subsidence.
Possible causes include:
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Normal settlement
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Drying shrinkage
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Thermal movement
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Minor seasonal movement
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Different materials expanding at different rates
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Poorly bonded masonry
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Movement between old and new construction
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Defective previous alterations
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Localised deterioration
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Structural movement
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Subsidence
The objective of a professional inspection is therefore not simply to establish that a crack exists.
It is to consider why the cracking may have occurred, how significant it appears to be and whether further investigation is required.
Which Type of Survey Do I Need?
The appropriate survey depends on the extent of the problem.
Structural Survey
Where there is extensive cracking, movement affecting several areas of the property, significant distortion or a genuine concern about subsidence, a more comprehensive Structural Survey may be appropriate.
This allows the wider structure and circumstances of the property to be considered rather than concentrating on one isolated defect.
If you are unsure, send us the property address, photographs and a brief description of what you have noticed.
We can then advise on the appropriate scope of inspection.
Specific Issue Survey
Where your concern relates to one particular defect or localised structural issue, you may not require a wider Structural Survey.
Our Specific Issue Survey is designed specifically for this situation.
Typical examples include:
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A particular crack above a door or window
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Cracking to one wall
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Movement around a bay window
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Cracking where an extension joins the original house
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A localised area of masonry movement
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A structural concern identified during refurbishment
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A particular defect highlighted by another surveyor
The survey concentrates on the particular issue identified rather than assessing the whole property.
Cracks Between an Extension and the Original House
Cracking where an extension meets the original property is a particularly common concern.
An extension and the original building may have been constructed many years apart and could have different:
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Foundation depths
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Foundation types
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Wall construction
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Materials
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Ground conditions
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Rates of settlement and movement
Cracking at the junction can therefore occur for several reasons.
It may result from relatively minor differential movement, poor bonding between the two structures or thermal movement.
Alternatively, it may indicate more significant foundation or ground movement.
An inspection can help determine which explanation appears most likely and whether further investigation is justified.
Trees and Subsidence
Trees are frequently mentioned when subsidence is suspected, particularly in areas containing shrinkable clay soils.
A mature tree can extract substantial quantities of moisture from the surrounding ground, and this can contribute to changes in clay soil.
However, simply having a tree close to a property does not mean that it is responsible for cracking.
Factors that may need to be considered include:
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Species of tree
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Size and maturity
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Distance from the building
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Soil conditions
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Foundation depth
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Position of the cracking
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Historic movement
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Seasonal changes
Where the relationship between vegetation and structural movement requires specialist investigation, arboricultural advice may also be recommended.
Can Leaking Drains Cause Movement?
Drainage defects can sometimes contribute to movement around a building.
A damaged underground drain may affect the surrounding ground, particularly where leaks continue for a prolonged period.
Where the pattern of cracking or movement suggests that drainage could be a factor, additional investigation may be recommended.
This could include a CCTV inspection of the drainage system.
A visual structural inspection cannot establish the condition of underground pipes, so where further investigation is required we will explain this.
Subsidence or Settlement?
The terms subsidence and settlement are sometimes used interchangeably, but they do not necessarily describe the same thing.
Settlement generally describes movement associated with a building or part of a building adjusting after construction.
Subsidence generally refers to downward movement of the ground supporting the foundations.
There are also numerous other forms of structural and building movement that can cause cracking.
Determining the likely cause requires consideration of the crack pattern together with the construction, age, alterations and surrounding circumstances of the property.
Subsidence and London's Clay Soil
Much of London is constructed over clay soils.
Clay soils can change volume as moisture levels alter. During extended periods of hot and dry weather, moisture can be lost and the soil may shrink.
The risk is not identical across London and the presence of clay does not mean that a property will suffer from subsidence.
Foundation depth, vegetation, drainage, construction type and local ground conditions all play a part.
This is one of the reasons why the circumstances of the individual property need to be considered rather than diagnosing subsidence from a photograph alone.
Buying a Property With Cracks?
Cracking is frequently identified during Building Surveys and other pre-purchase inspections.
A surveyor may recommend that a purchaser obtains further structural advice before exchanging contracts.
Depending on the nature and extent of the concern, this may require either a Structural Survey or a focused Specific Issue Survey.
Further investigation can help you understand:
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The apparent significance of the cracking
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Possible causes of the movement
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Whether the defect appears localised
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Whether further investigation is advisable
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Whether monitoring may be necessary
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Whether repairs are likely to be required
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Whether specialist structural input is needed
Where you are purchasing a property, it is normally preferable to investigate a significant structural concern before becoming legally committed to the purchase.
What If Cracks Have Suddenly Appeared?
New cracking should not automatically be treated as subsidence, but sudden changes deserve attention.
It can be useful to record:
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When you first noticed the crack
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Whether it appears to be increasing in width
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Whether doors or windows nearby have started sticking
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Whether cracking is visible externally as well as internally
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Whether recent building works have taken place
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Whether there are large trees nearby
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Whether there have been drainage problems
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Whether previous cracks have been repaired in the same location
Photographs taken periodically can also provide useful information about whether a crack is changing.
If you send photographs to Met Surveyors together with the address and a short description of the problem, we can advise what type of inspection appears most appropriate.
Will One Inspection Prove Whether Subsidence Is Active?
Not necessarily.
A visual inspection provides evidence about the condition of the building at the time of the survey.
In some cases the pattern and circumstances of movement may indicate a reasonably clear likely cause.
In other cases, further evidence may be required to determine whether movement is historic, seasonal or continuing.
Further investigation could include:
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Crack monitoring
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Drainage investigation
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CCTV drain inspection
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Trial holes to establish foundation depth
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Ground investigation
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Arboricultural advice
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Further structural engineering assessment
The appropriate investigation depends entirely upon the circumstances of the property.
Should I Contact My Buildings Insurer?
If you believe your property may be suffering from subsidence, you should check your buildings insurance policy and any requirements relating to notification of potential claims.
Met Surveyors can provide independent professional advice regarding the visible condition of the property, but our inspection does not replace any investigation that your insurer may require.
If an insurance claim is being considered, your insurer may appoint its own surveyor, engineer, loss adjuster or other specialist.
What Happens When You Contact Met Surveyors?
If you are concerned about possible subsidence or structural movement, you do not need to decide which service you require before contacting us.
Send us:
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The property address
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A brief description of the problem
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Photographs of the cracking or movement where available
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Details of approximately when you first noticed it
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Any previous reports or relevant information you already have
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We can review the information and advise whether the circumstances appear better suited to a Structural Survey or a Specific Issue Survey.
Specific Issue Surveys From £695 + VAT
Where you have one clearly defined structural concern, our Specific Issue Survey provides a focused inspection of that particular problem.
The standard service includes:
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Review of information supplied beforehand
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Site inspection of the reported issue
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Visual inspection of relevant accessible areas
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Consideration of the likely causes
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Photographic record where appropriate
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Written report
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Recommendations for appropriate next steps
The fee starts from £695 + VAT, subject to the size, complexity and extent of the issue.
This is not a comprehensive subsidence investigation of the whole property. Where the evidence indicates that a wider structural assessment is appropriate, we will advise you accordingly.
Structural and Subsidence Advice Across London
Met Surveyors provides structural survey and Specific Issue Survey services across London and the surrounding Home Counties.
If you have discovered cracking, movement or another structural concern, the important first step is establishing the appropriate level of investigation.
Send us photographs and details of the property and we can advise how best to proceed.