MET SURVEYORS

What Do Subsidence Cracks Usually Look Like?

 

Cracks associated with subsidence often have characteristics that suggest one part of a building is moving differently from another.

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Possible signs include:

• Diagonal cracking

• Cracks around doors and windows

• Cracks wider at one end than the other

• Cracking visible internally and externally

• Cracks that are becoming wider

• Previous repairs reopening

• Cracks concentrated in one part of the building

• Cracking associated with sticking doors or windows

• Cracking alongside sloping or uneven floors

• Cracks developing between an extension and the original house

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None of these features proves subsidence on its own.

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The surrounding evidence is equally important.

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Are Subsidence Cracks Always Diagonal?

 

No.

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Diagonal cracks are commonly associated with structural movement because openings such as doors and windows create weaker areas within walls.

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However, subsidence related movement can also create:

• Vertical cracks

• Stepped cracks through brickwork

• Horizontal cracks

• Cracking around corners

• Cracks at wall junctions

• Cracks around extensions

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The crack pattern depends on the direction of movement and the construction of the building.

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Subsidence Cracks on Internal Walls

 

Internal wall cracking is one of the most common reasons homeowners become concerned about subsidence.

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Possible signs include:

• Diagonal cracks above doors

• Cracks extending from window corners

• Cracks running through plaster and masonry

• Cracks that are reopening after decoration

• Cracking where one wall meets another

• Cracking close to floors or ceilings

• Cracking alongside door frames that have become distorted

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Internal cracking may be significant, but it should not be assessed in isolation.

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A crack limited to plaster may be cosmetic.

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A crack that also appears externally in a similar location may suggest movement through the wall itself.

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Subsidence Cracks in Plaster

 

Plaster cracks are extremely common and many have nothing to do with subsidence.

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Possible non structural causes include:

• Drying shrinkage

• Thermal movement

• Decoration

• Plasterboard joints

• Minor settlement

• Movement between different materials

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More attention may be required where a plaster crack:

• Continues into the wall behind

• Is becoming wider

• Reappears after repair

• Matches an external crack

• Forms part of a larger pattern of movement

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The key is determining whether the crack is confined to the finish or reflects movement within the building itself.

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Minor Subsidence Cracks

 

Homeowners often search for information about minor subsidence cracks.

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The difficulty is that the word minor can be misleading.

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A narrow crack may be relatively insignificant, but it can still be useful evidence if:

• It is new

• It is widening

• Similar cracks are appearing elsewhere

• Doors or windows nearby are sticking

• The property has a history of movement

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Conversely, a wider crack that has remained unchanged for decades may be historic and stable.

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This is why crack width alone should never be used to diagnose subsidence.

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Cracks Around Doors and Windows

Doors and windows are common locations for movement to become visible.

 

Possible patterns include:

• Diagonal cracking from corners

• Cracks above lintels

• Cracks beneath windows

• Cracks that taper in width

• Cracking alongside distorted frames

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Possible causes include:

• Settlement

• Lintel movement

• Structural alterations

• Differential movement

• Ground movement

• Subsidence

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Where cracking is accompanied by sticking doors or windows, further investigation may be sensible.

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Stepped Cracks Through Brickwork

 

External cracking sometimes follows the mortar joints between bricks.

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This creates a stepped appearance.

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Stepped cracking can indicate movement within the wall or foundations, particularly where:

• It is new

• It is widening

• Several steps are involved

• Cracking is also visible internally

• The wall appears distorted

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However, stepped cracking can also result from other structural or construction issues.

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It should be assessed in the context of the whole building.

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Cracks Wider at One End

 

A tapered crack can indicate differential movement.

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For example, one part of a wall may have moved more than another, creating a crack that is narrow at one end and wider at the other.

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This can occur through:

• Settlement

• Foundation movement

• Lintel movement

• Differential movement

• Subsidence

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Again, the crack shape is useful evidence, but not proof by itself.

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Cracks Visible Inside and Outside

 

Where a crack appears in a similar location internally and externally, it may indicate that movement extends through the wall construction.

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This can be more significant than a surface crack limited to plaster or render.

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Particular attention may be justified where:

• The crack is widening

• The pattern is repeated

• Doors or windows nearby are affected

• Floor movement is also present

• Previous repairs have reopened

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Cracks That Keep Coming Back

 

A crack that has been filled and decorated several times but keeps reopening can be significant.

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This may suggest that movement is continuing.

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Useful information includes:

• When the crack first appeared

• When it was repaired

• How long the repair lasted

• Whether the crack reopened in exactly the same place

• Whether it is now wider than before

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Repeated repairs without understanding the cause can simply hide the symptom temporarily.

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Cracks After Hot Weather

Prolonged hot and dry weather can sometimes contribute to movement where properties are built on shrinkable clay soils.

 

Possible signs include:

• New cracking after a dry summer

• Existing cracks widening

• Cracking concentrated close to mature trees

• Movement affecting one side of the property

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This does not mean that cracks appearing after hot weather are automatically caused by subsidence.

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Timing is one piece of evidence, not a diagnosis.

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Cracks Near Trees

 

Trees can influence ground moisture, particularly in clay soils.

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Factors that may be relevant include:

• Tree species

• Size

• Distance from the building

• Ground conditions

• Foundation depth

• Pattern of cracking

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A nearby tree does not prove that it has caused movement.

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Where necessary, arboricultural advice may form part of a wider investigation.

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Cracks Caused by Leaking Drains

 

Leaking underground drainage can sometimes affect ground conditions around foundations.

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Where cracking occurs near:

• Gullies

• Drainage runs

• Manholes

• Inspection chambers

• Previous drainage repairs

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further investigation may be appropriate.

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A CCTV drain survey may sometimes be recommended.

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Cracks Between an Extension and the House

 

Movement between an extension and the original house is very common.

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Possible causes include:

• Different foundation depths

• Different foundation types

• Initial settlement

• Poor bonding

• Thermal movement

• Ground movement

• Subsidence

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Fine stable cracking may be relatively minor.

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Wider or progressive cracking should be investigated.

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Cracks and Sloping Floors

 

Subsidence or settlement does not only affect walls.

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Floor movement can also provide important evidence.

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Possible signs include:

• Floors beginning to slope

• A noticeable step between rooms

• Cracked concrete floors

• Broken screed

• Repeatedly cracked tiles

• Gaps beneath skirting boards

• Localised sinking

• Doors dragging across the floor

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Where wall cracking and floor movement occur together, a wider structural assessment may be more appropriate.

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Can a Floor Crack Without Subsidence?

 

Yes.

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Concrete floors and screeds can crack because of:

• Shrinkage

• Poor installation

• Settlement of material beneath the slab

• Inadequate compaction

• Thermal movement

• Underfloor heating

• Local movement

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A cracked floor does not automatically mean that the foundations are moving.

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How Wide Does a Subsidence Crack Need to Be?

 

There is no single crack width that confirms subsidence.

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Crack width is useful information, but it must be considered alongside:

• Crack location

• Direction

• Pattern

• Age

• Whether it is changing

• Other signs of movement

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A relatively narrow crack that is actively widening may be more important than a wider crack that has remained stable for many years.

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Are Hairline Cracks Subsidence?

 

Usually, hairline cracks in plaster are not evidence of subsidence on their own.

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They are common in both old and new homes.

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Possible causes include:

• Drying

• Decoration

• Temperature changes

• Minor settlement

• Plasterboard movement

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Concern increases where hairline cracking forms part of a wider pattern or becomes progressively more significant.

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What Is More Important Than Crack Size?

 

Change.

A crack that is:

• Widening

• Lengthening

• Reopening

• Appearing alongside new cracks

• Associated with floor movement

• Associated with sticking doors or windows

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deserves more attention than one that has remained unchanged for many years.

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Can Subsidence Cracks Be Horizontal?

 

Yes, but horizontal cracking can also have several other causes.

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Possible explanations include:

• Wall movement

• Corrosion of embedded steel

• Lintel problems

• Roof spread

• Structural alteration

• Thermal movement

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Horizontal cracks should not automatically be labelled as subsidence.

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Can Subsidence Cracks Be Vertical?

 

Yes.

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Vertical cracking can occur where one part of a structure moves relative to another.

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However, vertical cracks are also commonly associated with:

• Movement joints

• Shrinkage

• Poor bonding

• Extension junctions

• Changes in construction materials

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Location and pattern are critical.

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Should You Fill a Crack Before It Is Investigated?

 

If a crack is causing concern, it can be useful to photograph and record it before carrying out cosmetic repairs.

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Repeatedly filling a crack without understanding why it has appeared can make it harder to assess whether movement is continuing.

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Where practical, record:

• Date

• Approximate width

• Length

• Location

• Photographs

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Should You Monitor Subsidence Cracks?

 

In some cases, monitoring can help establish whether movement is continuing.

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This may include:

• Dated photographs

• Manual crack measurements

• Formal crack monitoring

• Periodic inspection

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Monitoring may be recommended where movement is uncertain or appears seasonal.

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Where there are obvious signs of significant structural movement, a wider survey may be appropriate first.

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When Should You Worry About Cracks?

 

Professional advice should be considered where:

• Cracks are widening

• Several cracks are appearing

• Cracks are visible internally and externally

• Previously repaired cracks reopen

• Doors or windows begin sticking

• Floors begin to slope

• Floor slabs or screeds begin cracking

• Cracking appears suddenly

• Several connected areas are affected

• There is concern about subsidence

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When Is a Specific Issue Survey Appropriate?

 

Where you have one clearly defined area of concern, a Specific Issue Survey may be suitable.

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Examples include:

• One diagonal crack

• Cracking around one window

• One area of internal wall cracking

• Cracking at an extension junction

• One localised floor defect

• A defect identified in another survey

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The survey focuses on the particular concern and includes a written assessment with recommendations.