MET SURVEYORS

Why Monitoring Can Be Important Before Underpinning

 

Underpinning is a substantial intervention.

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Before recommending major foundation works, it can be useful to establish whether the building is actually still moving.

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Monitoring may help show whether cracks are:

• Stable

• Continuing to widen

• Seasonal

• Increasing slowly

• Associated with one particular part of the building

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This evidence can help determine whether further structural investigation is justified.

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Can Settlement Be Mistaken for Subsidence?

 

Yes.

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Settlement and subsidence are not the same thing.

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Settlement generally relates to movement that occurs as a building or part of a building adjusts after construction.

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Subsidence generally refers to downward movement of the ground supporting the foundations.

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An extension may settle differently from the original house without the whole building suffering from subsidence.

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This is one reason underpinning should not be discussed before the nature of the movement has been properly assessed.

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Can an Extension Need Underpinning Without the Main House?

 

Potentially.

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An extension may have:

• Different foundation depths

• Different foundation types

• Different construction

• Different ground conditions

• Different loading

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If the extension has inadequate foundations or is experiencing significant movement, remedial work may be limited to the extension rather than the entire property.

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The extent of intervention should match the actual defect.

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What About Sloping or Sinking Floors?

 

A sinking or sloping floor does not automatically mean the foundations require underpinning.

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For example, a concrete floor slab may sink because the material beneath it was poorly compacted.

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In that situation, the floor could move while the main walls and foundations remain relatively stable.

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Possible causes include:

• Settlement of fill

• Poorly compacted hardcore

• Deteriorated timber supports

• Failed joists

• Local floor construction defects

• Foundation movement

• Subsidence

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The first task is to establish what part of the building is actually moving.

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Does Cracking Mean the Foundations Have Failed?

 

No.

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Cracking can develop for many reasons unrelated to foundation failure.

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Examples include:

• Plaster shrinkage

• Thermal movement

• Lintel defects

• Poor masonry bonding

• Structural alterations

• Differential movement

• Settlement

• Local defects

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Foundation failure is only one possible explanation.

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How Do You Know Whether Underpinning Is Required?

 

A decision about underpinning may involve several stages of investigation.

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Depending on the property, these may include:

• Visual structural inspection

• Crack monitoring

• Level monitoring

• Trial holes

• Foundation investigation

• Ground investigation

• CCTV drainage survey

• Arboricultural assessment

• Structural engineering design

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The level of investigation should be proportionate to the evidence.

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Not every property requires every stage.

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What Is a Trial Hole?

 

A trial hole can be used to expose part of the existing foundation.

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This can help establish:

• Foundation depth

• Foundation width

• Construction

• Relationship to surrounding ground

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This information can be important where the adequacy of existing foundations is in question.

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Trial holes are not normally necessary simply because a crack exists.

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What Is Ground Investigation?

 

Ground investigation can provide information about the soil beneath and around the property.

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Depending on the circumstances, it may consider:

• Soil type

• Ground conditions

• Moisture

• Bearing characteristics

• Fill material

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This type of investigation may be appropriate where the cause of movement cannot be established from the building alone.

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Does Underpinning Fix the Cracks?

 

Underpinning is intended to address foundation support.

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It does not automatically repair all cracking or internal finishes.

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Once the structure has been stabilised and sufficient time has passed, additional works may be required to repair:

• Cracked masonry

• Internal plaster

• External render

• Decorations

• Floors

• Doors and windows

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The structural cause should normally be addressed before cosmetic repairs are completed.

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Are There Alternatives to Traditional Underpinning?

 

Depending on the cause and design requirements, alternative structural solutions may sometimes be considered.

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The appropriate method is a matter for the structural engineer designing the remedial works.

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Possible approaches may include:

• Local foundation strengthening

• Structural repair

• Ground improvement

• Piled solutions

• Drainage remediation

• Monitoring without immediate structural intervention

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The correct solution depends on the actual cause and extent of movement.

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How Much Does Underpinning Cost?

 

The cost can vary substantially.

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Factors include:

• Extent of the affected foundations

• Depth required

• Ground conditions

• Access

• Structural design

• Temporary support requirements

• Number of areas affected

• Internal reinstatement

• Drainage alterations

• Location of the property

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For this reason, meaningful pricing should normally follow structural investigation and design.

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Quoting an underpinning cost before establishing what work is actually necessary can be misleading.

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Should You Get Several Quotes for Underpinning?

 

Yes, once a clear structural design and scope have been established.

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However, obtaining contractor quotations before the problem has been properly diagnosed can result in different contractors pricing completely different solutions.

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The sequence should normally be:

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Investigate the movement

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Establish the cause

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Determine whether remedial work is required

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Prepare the structural solution

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Then obtain comparable contractor quotations

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What If a Builder Recommends Underpinning?

 

A builder may identify obvious signs of movement, but the need for underpinning should normally be determined through appropriate structural investigation and design.

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The contractor who carries out the work should ideally be working to a clear professional specification rather than deciding the extent of structural intervention on site.

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What If an Insurance Company Is Involved?

Where the property is subject to a subsidence insurance claim, the insurer may appoint:

• A loss adjuster

• A surveyor

• A structural engineer

• Other specialists

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The insurer may want movement monitored before deciding whether structural repairs are necessary.

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If you believe you may have an insurance claim, check your policy and notification requirements.

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Does Underpinning Affect Insurance?

 

A history of subsidence or underpinning may affect future insurance.

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Possible issues can include:

• Premiums

• Policy excess

• Availability of cover

• Additional questions during quotation

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If you are considering buying a previously underpinned property, it is sensible to investigate insurance before exchange.

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Does Underpinning Affect Mortgageability?

 

It can.

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A mortgage lender may request supporting information where a property has a history of significant movement or underpinning.

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They may want to see:

• Structural reports

• Completion documentation

• Monitoring records

• Insurance information

• Details of remedial works

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A properly documented historic repair may be viewed very differently from unexplained structural work with no supporting records.

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Buying a House That Has Been Underpinned

 

Underpinning does not automatically mean you should avoid the property.

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What matters is understanding:

• Why it was needed

• When it was carried out

• What part of the building was affected

• Who designed the work

• Whether Building Control was involved

• Whether documentation is available

• Whether monitoring took place

• Whether further movement has occurred

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A well documented repair can provide much more reassurance than undocumented structural work.

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When Is a Specific Issue Survey Appropriate?

 

Where you have one localised structural concern, a Specific Issue Survey from £695 + VAT may be the appropriate starting point.

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Examples include:

• One significant crack

• Cracking around one opening

• Movement at an extension junction

• One localised sloping floor

• A particular defect identified by another surveyor

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The survey provides a focused inspection and written recommendations.

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When Is a Crack Monitoring Programme Appropriate?

 

Monitoring may be useful where:

• Cracks have reopened

• Movement may be seasonal

• It is unclear whether movement is continuing

• Subsidence is suspected

• The building appears stable but uncertainty remains

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If monitoring is recommended during the initial Specific Issue Survey, the instruction can normally be upgraded to our Crack Monitoring Programme from £1,395 + VAT total, saving £300 + VAT against commissioning it separately.

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When Is a Wider Structural Survey More Appropriate?

 

A Structural Survey may be appropriate where:

• Cracking is widespread

• Several elevations are affected

• Floors are also moving

• Several openings are distorted

• There are significant foundation concerns

• Major previous structural work has taken place

• The overall condition of the structure needs to be assessed

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Do Not Assume Underpinning Is the First Step

 

If you have found cracks in your home, the first question should not be:

“How much will underpinning cost?”

The first questions should be:

Why has the building moved?

Is it still moving?

What level of investigation is justified?

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Only once those questions have been answered should significant structural repairs be considered.

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Concerned About Subsidence or Underpinning?

 

Send Met Surveyors:

• The property address

• Photographs of the cracking

• Details of when it first appeared

• Whether it appears to be changing

• Photographs of any sloping or sinking floors

• Information about nearby trees

• Details of drainage problems

• Any previous structural reports

• Any information about historic underpinning

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We can advise whether the appropriate starting point is a Specific Issue Survey, Crack Monitoring Programme or wider Structural Survey.