While the majority of our structural engineers’ reports result from surveyors reports’ and lenders’ valuation surveys, an increasing number of reports are arising from buildings insurance and specifically subsidence cover issues.

These problems include:

1. a) Buyers who are unable to obtain subsidence insurance
2. b) Buyers who are unable to secure a mortgage because of historic underpinning or insurance claims.
3. c) Vendors who are unable to sell their home as there is no subsidence insurance in place.
4. d) Vendors who are unable to sell their property because of historic underpinning or minor subsidence claims and superficial repairs, for example, redecoration.
5. e) Owners insurance premiums increase or even withdrawn without notice.
6. f) Owners who require a structural engineers report to support their application for new insurance terms
7. g) Owners re mortgaging are asked for a Certificate of Structural Adequacy to secure new funding even thought current insurance includes subsidence.
8. h) Owners subsidence insurance is withdrawn after they have made a claim or even merely notifying the insurer of damage without submitting a claim.

So why are there so many insurance problems related to subsidence?

Readers will see from the points above that the entire property chain, ranging from simple home ownership to buying and selling, is fraught with subsidence insurance issues.

Whilst we are not insurance experts, we believe that many of the issues arise from a simple lack of understanding of the subject. The following points are clear to us:

1. a) Property prices are so high that the general public, including insurance company employees, instinctively view cracks in buildings, such as houses and flats, as a significant concern or risk.
2. b) Most people believe that any cracks in houses are an issue, however, most are not.
3. c) Many people think that cracks in houses are expensive to repair and will jeopardise the process of buying and selling a property. In reality, most cracks are neither serious nor expensive to repair especially when compared to the property’s value.
4. d) Insurance companies do not employ technical experts, such as chartered structural engineers, which means they often don’t fully understand the technical issues. Instead they rely on binary computer-generated answers to standardise questions, which is too simplistic a methodology.

Discussion

The starting point with all of these issues is the “risk” specifically “perceived risk”. It all stems from a misunderstanding of how buildings behave and what cracks mean or do not mean. Fear of the unknown perpetuates anxiety until an experienced Chartered Structural Engineer provides a report and clarifies the situation.

It is a requirement of any domestic mortgage that the buyer or owner includes subsidence insurance as part of their buildings insurance policy. The insurance industry provides associated insurance and has to price the risk and ensure premiums to cover the overall costs and contribute to profits, similar to other types of insurance.

Between the 1970s and the 1990s, insurance policy excesses were typically low, around £500. Consequently, large numbers of the public did not hesitate to file insurance claims for minor issues such as small cracks or seasonal movement since the cost of repairs and redecoration nearly always exceeded the policy excess. As an unintended benefit, this often resulted in many rooms being newly decorated leaving them as good as new.

Whilst this article is not the place for a technical engineering thesis, it is fair to say that the subsidence industry, including engineers and surveyors, were somewhat overzealous when dealing with small amounts of cracking. This resulted in expensive underpinning schemes being carried out at huge cost, which was disproportionate to the cost of simply repairing the damage and dealing with offending trees. This legacy has resulted in owners, buyers and insurers being nervous of the terms ‘subsidence’ and ‘underpinning’ as these convey both expense and risk!

These days, it is uncommon to see properties being underpinned. Instead, issues such as tree roots or leaking drains are addressed, followed by straightforward and cost-effective crack repairs.

Insurance primarily aims to repair and restore the pre-damage condition rather than improve it or prevent future damage. A helpful analogy is that of a vintage car: if a fault develops, it is repaired, but the car does not become like new, and the same issue may arise again. Insurance companies have become more stringent in handling claims and prefer to repair damage even at the risk of future repairs, as this is potentially less costly than investing significantly more to prevent recurrence.

As a consequence, the cost of insurance per claim has reduced significantly, yet many household insurance companies are unprepared to offer simple and affordable terms to most domestic homeowners. This leads us to believe that the past perception of expensive underpinning is unfounded.

Why do we all worry about cracks?

This article is not a technical thesis on cracks and the human and engineering implications but it is important to emphasise that most of the issues discussed here are a result of people misunderstanding cracks and what they mean for residential property. Those interested to read more can see separate articles on our blog website about subsidence and minor cracks.

Previous claims and underpinning

Insurance companies often penalise property owners or buyers who have a history of previous insurance claims, especially if underpinning has been carried out. While various issues may arise from this stance, it often lacks sense from a technical and engineering perspective. Insurance firms most likely use simplified algorithms for these evaluations, as employing a structural engineer to assess each case individually is unrealistic. However, property owners or buyers can seek their own expert by employing a chartered structural engineer to assess the situation more accurately and provide a structural engineers’ report.

In the majority of our inspections and reports, where previous insurance claims have been made or underpinning has been carried out, we find that the current and future risks are no different to those of many similar properties in the same geographical area, sharing a similar architectural style and foundations. With over 30 years of experience, it appears that the criteria used by insurers and brokers are far too simplistic, leading to broad generalisations that cause problems for numerous homeowners and potential buyers.

What should you do?

Most of the issues discussed are unfortunate and frequently avoidable if there was a greater involvement of engineers in the decision-making process. This is unlikely to change given the sheer size of the insurance world. However, homeowners and potential buyers can significantly influence the decision making processes by exercising due diligence. This involves appointing an experience Chartered Structural Engineer to advise them. And the insurance company should be reassured by the subsequent detailed report. At the very least, it will provide essential engineering facts and give the insurance company concrete information on which to base their decisions (no pun intended!).

Although this is an extra task and expense, it can be crucial for securing subsidence insurance, which may affect the ability to purchase certain properties. For existing homeowners, it may significantly impact future annual insurance premiums. In many cases, the report’s cost can be recouped within one or two years through substantial insurance savings.

Should you require further advice or have any questions then do call SERL on 020 8161 9900 or contact us and we’ll be delighted to help.

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Pre-purchase Structural Engineers Reports are frequently called for during the sale of residential property on matters such as cracks, fears of subsidence or settlement or general structural problems noted but not diagnosed in a Chartered Surveyor’s report. These reports are primarily for mortgage purposes or RICS Level 1 or 2 Surveys.

The qualifications required for preparing reports by institutional lenders and building insurers can vary significantly. While Chartered Building Surveyors were once commonly tasked with this role, Chartered Structural Engineers are now often preferred. However, both lenders and property buyers often mistakenly believe that these inspections and reports are conducted by fully qualified, expert, and experienced Chartered Engineers.

Prospective clients often draw parallels with consultations involving top medical professionals, like an orthopaedic surgeon, who they expect to be highly qualified. They do not expect the patient, in our case, the property, to be evaluated by a junior doctor who merely discusses their findings with a senior colleague before the latter signs off on the prognosis.

For 35 years, my practice, SERL, has always used Chartered Engineers for such important pre-purchase reports, though this is not common. It often surprises prospective clients to learn that these structural inspections can be conducted by junior staff members, as long as a Chartered Engineer within the same organisation reviews and signs off the report. This process ensures the report meets lenders’ requirements if appropriate.

It is common for multiple staff members to be involved in the somewhat leisurely handling of “subsidence claims” for property owners and insurers. However, I argue that this approach is not appropriate for point-of-sale reports for the following key reasons:

a) Pre-purchase Inspections and reports are normally urgent and arise immediately prior to exchange of contract or at the eleventh hour when mortgage offers are urgent. They are “one offs” with little time for reflective thought or involving others.

b) Pre-purchase Inspection and reports are quite unlike Subsidence claims or general advice to owners since there is no practical prospect for investigations, monitoring of cracks or soil testing.

c) Reports require a lot of knowledge and expertise to determine likely the cause of structural issues with little time to “dig deeper”.

d) The financial and contractual importance of an expensive property purchase should be matched by the importance of the expertise and qualifications of those advising.

e) The need for a Structural Engineers Report has already been identified by a Chartered Surveyor so it now requires a more expert and experienced set of eyes than the Surveyor.

f) Third party Lenders and Insurance companies are relying on the same advice that we provide the prospective buyer, so they are entitled to assume it is an experienced and qualified opinion.

g) My practice, SERL, has encountered some truly shocking reports prepared by inadequately qualified individuals. These reports are rejected by lenders and insurers, damaging the reputation of our esteemed institution.

My proposal

I propose that such reports should only be carried out and signed by a fully qualified Chartered Engineer, not a graduate or technician engineer. This is normally a Chartered Structural Engineer with qualifications CEng MIStructE. Alternatively some Civil Engineers have relevant residential building experience so the qualification CEng MICE may be applicable where experience applies.

For the reasons set out above, and with no disrespect intended to less qualified Engineers, the pressures of time and the need for a “one off” structural inspection and report does not allow for a process of less qualified people carrying out inspections and the matter then being referred to a more senior person in the office for a signature.

Simon Pole BSc CEng FIStructE MICE MRICS MAE

Simon is a dedicated Chartered Structural Engineer. He actively conducts daily Structural Engineers Reports for clients covering the Greater London area. He is extensively involved in numerous professional interest groups and has lectured widely to Structural Engineers, Surveyors, and Party Wall professionals.

His voluntary contributions to the Institution of Structural Engineers include helping graduates prepare for their professional examinations and advising the professional conduct committee on matters within his expertise, as well as on general ethical and professional standards.

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A prospective buyer contacted SERL based on recommendations from their valuation surveyor. They needed a report to address the concerns of their mortgage surveyor, who identified structural issues associated with both general external and internal cracking.

The surveyor had endorsed SERL Structural Engineers Reports as a reputable, independent, and highly experienced structural engineering firm practising in the Sheen and Richmond area of South West London.

SERL’s structural reporting service

In response to the client’s requirements our qualified Chartered Structural Engineer recommended a General Structural Inspection (GSI) report.

SERL offers two types of structural reports:

1)       A localised, specific, and limited Specific Structural Inspection (SSI) report or a Structural Engineers Defect Report.

2)       A broader General Structural Inspection Report (GSI) or Structural Engineers General Movement Report which focuses only on matters of cracking and movement.

Our Chartered Structural Engineer’s report for the South West London property

The property is a right-hand semi-detached family home, likely built in the early 1900s based on its architectural style. It is situated on a relatively flat site, which our geological mapping suggests is probably Kempton Park Gravel.

The interior decoration is in extremely poor condition and appears to have been neglected for about thirty to forty years. Consequently, there are more internal cracks than one might typically expect.

SERL’s findings

The rear elevation of the property exhibited one significant crack that will require a thorough resin repair as part of regular maintenance. However, this issue does not affect our assessment of the property’s value or risk from a purchase or loan perspective.

Overall, the alignment and stability of the house is good, and better than many other properties we survey. This is evident in the straightness of the brickwork and the alignment of door and window sills.

Occasional spirit level checks indicated minor undulations in the alignment of the window sills and brickwork, which are within acceptable standards, especially for a property of this age.

SERL’s conclusions and recommendations

We were confident that the structural issues could easily be repaired for a few hundred pounds, which would allow the purchase to proceed.

We were able to provide a positive report to the client, who was pleased with our advice and guidance, and we expect that the mortgage company was able to approve the loan.

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Introducing Certificates of Structural Adequacy or COSA for short

This article explores the topic of Certificates of Structural Adequacy (COSA) within the context of buying and selling a residential property. Specifically, how they relate to a Structural Engineers Report for a buyer or, on occasion, a seller.

Certificates of Structural Adequacy (COSA) were established by the Institution of Structural Engineers in 2000. These certificates are important where a property has either been underpinned or had various structural cracks repaired within the last 20 years. See background below.

A COSA is NOT a form of Guarantee or Warranty and is often misunderstood. It is actually a concise, single-page document summarising relevant events, associated documents, company details, and a list of documentation. See below.

Increasingly, COSAs are requested by buyers’ solicitors, lenders, insurance companies, and surveyors before purchasing a property. See below.

What is a Certificate of Structural Adequacy and what it excludes

A Certificate of Structural Adequacy typically consists of a one-page summary of a major insurance claim related to subsidence. This may involve underpinning and/or significant superstructure crack repairs. Prepared by the lead consultant, the document summarises the entire process from start to finish, including initial reporting, investigations such as soil testing and crack monitoring, as well as the eventual design, specification, and site inspection of the repairs.

Since about 2020, there has been an increasing trend in the request for Certificates of Structural Adequacy during the pre-purchase Structural Engineers Report process. This typically occurs when evaluating cracking, movement issues, or providing advice on potential structural concerns during property transactions, regardless of previous occurrences such as subsidence or underpinning.

At SERL POLE, we issue these certificates clearly outlining their limitations, ensuring that clients fully understand them.

Defining what a COSA is NOT

Crucially the Certificate of Structural Adequacy (COSA) is neither a guarantee nor a warranty. It does not substitute for the guarantee from specialist underpinning or repair contractors, which may still be valid or might have expired. The COSA does not replace the need for a comprehensive Structural Engineer’s Report and can only be issued alongside such a report. Additionally, if the report concludes that the property is not “structurally adequate,” the COSA cannot be issued.

A COSA serves as a summary of the one off visual inspection and issue of a Structural Engineers Report, if that is the extent of the engineers’ evaluation. This excludes any intrusive investigation’s, crack monitoring, or similar activities, which are impractical during the sale process due to time constraints.

A COSA is a useful summary for those who prefer a concise report and do not wish to read the “small print” and the title can convey reassurance and confidence in the findings. This simplicity is likely why solicitors and lenders appreciate the concept.

This additional value of the Certification process does incur a commercial fee as it requires significant professional time and resources to explain the details to all parties involved. It is an extra service over and above our standard structural engineering reports.

It is important for SERL to clarify that the Certificate itself does not confer any contractual obligations beyond what is detailed in the written report, with which it should be read in conjunction. All our professional opinions are included within the formal report, which should be sufficient for most clients without necessitating a Certificate. Nevertheless, demand for COSA Certificates is rising due to the reasons outlined.

Should you have a Certificate of Structural Adequacy?

There is not a simple answer to this question. However, a COSA is becoming increasingly popular particularly amongst those selling their home because they add value to the vendors information pack providing reassurance to the buyer if the property appears sound.

Buyers sometimes obtain a COSA for similar reassurance, however, they are more frequently instructed to do so by their prospective lender or building insurer or via their surveyor.

We advise all our clients to carefully consider the limitations of such a Certificate as they do not provide any guarantee or warranty as detailed in this article.

Background

Since the turn of the millennium, Certificates of Structural Adequacy have been integral to the underpinning and building insurance sector. At that time, the collaboration between the Institution of Structural Engineers and a multi-party group, from the insurance and underpinning industry, determined that major subsidence claims should be summarised by the supervising engineer or loss adjuster.

Certificates of Structural Adequacy (COSA’s) were commonly issued following the underpinning of properties suffering from subsidence and they provided a useful resume of the lengthy Insurance claims process from investigation, design, specification and supervision of repairs.

COSA’s were not generally used by the wider construction or building industry.

COSA’s were not used by Surveyors and Structural Engineers who were not involved in the investigation, specification and supervision of building works.

COSA’s were not used, until very recently, by Structural Engineers carrying out a pre-purchase Structural Engineers Reports, where a one off opinion has been provided but with little or no knowledge of the subsidence history of a property.

The COSA has primarily been used in the insurance industry for procuring subsidence repairs. This involves a series of well-established, detailed procedures to investigate causes and implement suitable remedial actions, requiring the input and expertise of property professionals. Many experts and trades people contribute, including consulting engineers, geologists, arboriculturists, drainage experts, crack monitoring specialists, underpinning professionals, and general contractors. The whole process can often exceed a year. The need for a lead consultant to efficiently summarise the scope, parties involved, and actions taken in one succinct document led to the creation of the COSA in the late 1990s.

The COSA has not replace the professional responsibility of the parties involved and each service provider remains responsible for their advice according to their normal terms of client instructions and terms of business, also backed by their professional indemnity insurance. The specialist underpinning contractors normally provide a 10 year guarantee for their own works.

Today’s Certificate of Structural Adequacy

Since 2020, SERL POLE has noted that institutional lenders, insurance companies, and certain conveyancing solicitors frequently request a Certificate of Structural Adequacy (COSA) for any property purchase. This is regardless of whether there is a history of subsidence or underpinning.

From the above it is immediately clear that this was not the intention of the COSA and there is much misunderstanding even within the professions, regarding its appropriateness.

The limitations of a pre-purchase survey of any sort when the buyer or client is not the owner of the property, time and money constraints, together with all manner of practical implications, mean that it will never be possible to dig holes, test the soil, monitor the cracks for a year, and produce a report which states the property is fine, or structurally adequate.

As Chartered Structural Engineers we are able to assess the strength and stability of a property through a one-off, non-invasive inspection and provide their professional opinion. If a property is deemed “Structurally Adequate,” we will say so. Should the property need clear repairs without further investigations, we outline these in general terms and can confirm “Structural Adequacy” conditional upon such repairs.

By separate agreement beyond the visit and report fee, we can issue a Certificate of Structural Adequacy, provided the client acknowledges its limitations as outlined above. This certificate is not a guarantee or warranty but a summary of the report, with certain convenience and commercial advantages.

Surveyors, Banks and Lenders health warning

We would ask other property professionals to be fully aware of what a COSA is and is not, since they are often called for by lenders and Insurers during the pre-purchase process where RICS Surveyors Reports have recommended a Structural Engineers Report on behalf of the buyer.

It is essential for all parties to understand that when advising a buyer, the structural engineer’s role is limited to a single visit and report. The engineer cannot conduct detailed investigations into structural defects, such as monitoring cracks or testing soil, due to pre-purchase time constraints and because the buyer, not owning the property, is not technically the engineer’s client. As a result, the engineer cannot risk damaging the vendor’s property or create a conflict of interest by serving both buyer and vendor. Some lenders mistakenly request a “Certificate,” believing it provides insurance, indemnity, or warranty, when in fact, it does not exist.

Further Clarification and helpline

If readers of any status whether buying or selling or fellow professionals have any questions regarding this article, we will be very pleased to speak to you, so do not hesitate to call Structural Engineers Reports Limited on 020 8161 9900.

References

1. Subsidence by Institution of Structural Engineers published November 2023.

2. Subsidence of Low Rise Buildings second edition August 2000 Institution of Structural   Engineers

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Calling all industry professionals!

Has anyone in the industry had the chance to see/use/benefit from the above data which has just been published by the British Geological Survey? It sounds very useful indeed if it brings together not only the geological maps we are all used to, but in addition, information on building types and trees in particular in the case of classical clay subsidence.

The GBS promotional material lists the following considerations below. These are similar to those used in our own risk assessments that we use for our pre purchase Structural Engineers Reports but obviously brings together huge amounts of data which we cannot match individually:

• Geology including clay thicknesses/depths
• Building type and number of storeys
• Building age
• Drainage
• Tree proximity (the key one for clay soils)

All of the above apparently produces a combined hazard score.

Insurance companies and conveyancing professionals are likely to find the information invaluable. However, we engineers and surveyors will be quick to point out that there’s no substitute for a property-specific survey. Such surveys consider all factors, including internal alterations and condition, which even advanced tools like Google Maps and AI haven’t fully matched yet.

Any thoughts and experiences from fellow professionals would be most welcome once the data is in use.

If anyone would like to share knowledge on this subject please e mail Simon.pole@Ser-l.co.uk or comment on the SERL Linkedin page

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Selecting builders and trades people poses numerous challenges for the public, a difficulty even industry professionals encounter. However, there are some helpful tips and pitfalls to watch out for. Having worked in the industry for 40 years, and conducted surveys and inspections where issues have arisen, I thought it might be useful to share my experiences to assist homeowners.

An overview

The public often has a negative perception of the building industry, anticipating unreliable suppliers, unexpected costs, and project delays. However, this perception does not reflect the experience of professionals within the construction sector. How can you as homeowners benefit from this insider knowledge?

The industry does have systemic issues within certain parts of the industry, being largely unregulated and populated by individuals with varying levels of experience and often lacking formal qualifications.

While the Internet offers easy access to suppliers, and numerous websites display impressive profiles for “approved” contractors, navigating these options can be a minefield despite improved quality assurance from these portals.

Often, as consumers, we contribute to problems in construction projects by prioritising the lowest price over detailed briefing and specifications, and wonder why it then goes wrong! We rarely buy the cheapest clothes or television or anything else in our lives that matters so why would we use this basis when working on our own homes which is probably our most expensive and prized asset of all?

The larger construction companies have stopped hiring apprentices or providing in-house training. Instead they prefer to outsource to specialised subcontractors, such as plumbers and electricians, hiring them as needed and releasing them once their tasks are completed. Many of these specialist trades operate as small businesses or independents, lacking the resources, financial stability, or job security to train employees on a permanent basis. Consequently, the industry is dominated by “one-man bands,” which limits opportunities for “on the job” learning and skill sharing, ultimately undermining quality and craftsmanship.

So how do you find the right person for the job?

Firstly, what to not to do when looking for a builder

Do not rely solely on the Internet, attractive advertisements, or professionally branded vehicles when selecting a builder as appearances can be misleading.

Even websites that verify a company’s proficiency often prioritise advertisers over those with established reputations who don’t require advertising as they have plenty of work.

While these portals might perform due diligence on the financial stability, insurance, and customer satisfaction of a company, they do not necessarily assess the technical competence to do the work. The technical ability to execute projects to a high standard, which professionals in the construction industry can confirm, is the most important criteria. Most builders recommended by architects and engineers do not need to advertise for work.

DON’T ask a friend

Asking for recommendations from friends or neighbours is a common approach which may work occasionally but usually doesn’t end well in our experience. While they often mean well, friends may recommend a contractor based on traits such as being “nice” or punctual, without the expertise to assess the technical quality of the work. For example, they might not recognise whether the right materials were used or if they meet the necessary strength requirements.

Other factors

Additionally, numerous financial and contractual issues deserve attention.

Questions such as whether your documentation forms a legally binding contract, if the pricing is fair, or whether payment should be made upfront are vital. It’s important to determine who is responsible for notifying local authorities under Building Regulations. Whether the Party Wall Act is applicable, and if landlord consent is necessary for flats or leaseholds. Also whether there are adequate plans and documentation to satisfy a landlord’s requirements.

Homeowners often face numerous complex issues they are unlikely to understand, and it may not be in a builder’s interest to clarify these matters fully. Some builders are unaware of when work needs to be reported to the Local Authority under Building Regulations or the Party Wall Act 1996, leading to complications that could be easily avoided. Even when projects seem to proceed smoothly, lacking formal approvals and paperwork can complicate future buying and selling of a property.

What should I do when looking for a builder or trades person?

The best course of action is to consult and appoint an industry expert, such as a professional, to manage the challenging tasks for you. This includes preparing specifications, scopes of work, and associated drawings, as well as obtaining quotes from their exclusive list of builders.

Chartered Architects, Chartered Building Surveyors, and Chartered Structural Engineers in London have dedicated their careers to making these precise selections for clients such as you.

You may think this sounds expensive, but be assured, faulty building work is far costlier than doing it right the first time. Building projects are inherently expensive. However, poor workmanship can lead to even greater expenses, beyond just monetary costs. The stress, delays, and lack of control contribute significantly to the overall burden, both financially and emotionally.

It is important to research and find the right professional based on their expertise, type, and size of work. As long as they are chartered and qualified, you should receive unbiased and professional advice.

If a project is too small, too specialised, or involves only one or two trades, local and smaller professional practices are only too happy to assist their local community by recommending suitable specialist contractors. This guidance is often offered as a professional courtesy and typically does not incur any charges.

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When purchasing a property in Greater London, contacting the Local Authority as part of your searches will provide guidance on the risks of subsidence, landslip, and heave. This information is based on statistical factors such as local geology and insurance company data on subsidence claims in your postcode.

Subsidence claims are most frequent where London Clay is near the ground surface and large mature trees are nearby. Consequently, the risk to a specific property depends on various factors, though some general tips and guidance can be offered.

While this advice is intended to inform, it is not meant to alarm potential buyers or sellers or suggest that all properties in a particular London area, town, or postcode are affected by these risks. On the contrary, due to proactive measures by most Local Authorities to maintain trees, these risks have decreased in recent years.

The following general guidance may be of interest:

1. Geological Map of London, the South East, and the UK

The British Geological Society (BGS) offers a free website and app that provides likely geological details for any postcode. This resource needs careful use but can help establish whether a property is located on clay soil.

The map uses two distinct layers to show the deep underlying bedrock, i.e. the soil very deep below the ground, together with the superficial geology which is the most important soil type as this is closest to ground level. This is likely to be the soil type found immediately below most foundations in period houses built before the war and even before 1976.

If no superficial geology information is recorded for a postcode, this indicates that the surface geology is the same as the bedrock – generally London Clay in most of Greater London, or chalk near the North Downs in Surrey, for example.

General soil types and associated risks:

– London Clay: High risk of subsidence especially with large nearby trees.

– Head: Intermediate risk with nearby trees.

– Alluvium: Soft soil with a risk of historic settlement.

– Langley Silts: Clay with silt.

– Gravel Soils (e.g. Kempton Park, Taplow, Lynch Hill, Hackney) – Generally more strong and stable than clays and other soils listed above.

2. Trees

Most significant subsidence cases on clay soils involve trees or mature shrubs. The risk of subsidence depends on the location and size of the tree if the superficial or outcropping bedrock is clay-based. Conversely, stable soils like sand, gravel, or chalk reduce this risk. However, large trees can disrupt drains, potentially leading to subsidence due to soil softening or erosion.

Useful guidance regarding trees:

a) Consider the proximity of the tree to the house. If a tree’s height exceeds its distance from the house, root systems likely extend beneath the property.

b) Determine if the tree is within your control (i.e. within your property boundary) or on neighbouring or local authority land.

c) Check if the tree is protected by a preservation order or if the property is within a conservation area, requiring local authority approval for any alterations.

d) If a tree is suspected to cause subsidence damage, the tree owner may need proof, such as soil and root testing, to address the issue.

3. Drainage Issues and Loose Soils

Period houses often rest on manmade materials known as fill, covering London’s natural geology, whether gravels or clays. As a general guide, if loose soils are near the surface and below the house foundations, softening and erosion may occur, especially with poorly maintained drains located beneath or adjacent to the house. Subsidence can result from drains even when sands and gravels are close to the surface, not just clay soils. Given that drain surveys are relatively inexpensive, it is prudent to include these in early maintenance plans when purchasing a property. Requests to test drains pre-purchase can delay transactions, with some vendors reluctant to undertake such testing. Fortunately, drainage repairs are typically affordable, often costing a few thousand pounds rather than tens of thousands.

4. Foundation Depths

Subsidence risk is heavily influenced by foundation depth. Shallow foundations are more susceptible to soil drying out and shrinking during summer, tree root intrusion, and proximity to drains. Deeper foundations are generally more stable, with reduced susceptibility to seasonal soil volume changes and tree root impact. Modern properties typically feature deeper and more robust foundations, especially following the design improvements post-1976 after the significant summer drought.

Houses with cellars benefit from naturally deeper and more stable foundations. Houses with lower ground floors are usually better protected by having most of the property and foundations significantly below street level where trees are located. This might not apply to trees in rear gardens, however, where the external ground level is often close to lower ground floor level.

Foundation Depth Guide:

– Pre-1920: 30 cm to 45 cm

– 1920-1930s: 45 cm to 60 cm

– 1950-1975: 60 cm to 1 m

– Post-1976: 1 m or deeper

5. Building Regulations Approved or Engineer-Designed Foundations

Modern foundations are generally more robust, particularly if approved by the Local Authority Building Control Department or designed by a Chartered Structural or Civil Engineer based on soil testing and considering the mature height of nearby trees.

Note: that self-contained conservatories with external doors to the main house often do not comply with Building Regulations.

Local Authority approvals are based on current site conditions, not future tree heights, and the Authority holds no design liability. Therefore, consulting a reputable firm of chartered Structural Engineers for foundation designs of extensions and new constructions is advisable.

The National House Building Council (NHBC) offers extensive guidance to designers and developers for building near trees on clay soils, considering the soil’s shrinkage characteristics determined by testing or assumed worst-case scenarios. Tall trees, such as large oaks, London Planes, and Poplars, can necessitate foundation depths or underpinning up to 3.5 meters.

For new foundations exceeding about 2 meters, alternative methods like bored piles, concrete stilts drilled deep into the ground with a reinforced slab or a series of linking beams on top, are often more economical and practical.

Conclusions

This article serves as a general overview and should not be used in isolation without obtaining location-specific advice from relevant professionals, such as a local chartered structural engineer. It aims to provide valuable insights for property owners and non-engineering professionals, including solicitors, general practice surveyors, and estate agents, on broad geological and structural matters.

The paper introduces the geology of the London area and provides guidance on how to use the British Geology viewer map or app to identify the most likely soil type for a specific address or postcode. It explains the distinction between bedrock and superficial geology, as well as the differences between clay soils and gravel/sandy soils. Guidance is also provided on typical foundation depths for buildings of different ages.

This article highlights the importance of considering trees on clay-based soil, and the potential mature height of a tree if it isn’t controlled. This is crucial when designing foundations for extensions or new buildings. While it aims to be informative, we recommended you consult with a chartered structural engineer for more specific advice.

The post Subsidence risks for properties in London appeared first on Structural Engineers Report.

1. A) Consultancy advisory reporting advice
2. B) Design advice – calculations and drawings.

This article focuses on category A, since this is the expertise of Structural Engineers Reports Limited, a structural engineering firm, with nearly forty years of experience in London and the Home Counties.

Chartered structural engineering – A specialist approach

Chartered structural engineering is a very specialist discipline within construction and the built environment. General advice tends to be provided by chartered surveyors for residential buying and selling, chartered building surveyors for the technical and commercial sector, and architects provide advice related to design, town planning, and building regulations.

A useful analogy can be made with the medical profession: a general practice doctor (GP) is like a general practice surveyor where buying and selling residential properties is concerned. Similarly, a structural engineer, as a specialist, is comparable to a heart or knee surgeon or other specialised consultant in medicine.

There are very large firms of chartered structural, and civil engineers who design and advise on all manner of commercial and industrial buildings, bridges, airports, and similar large-scale infrastructure projects. These firms rarely deal with the residential sector as they tend to work for repeat clients on extensive projects.

In contrast, the residential sector is generally served by small and medium-sized companies (SMEs), particularly those with one to ten employees.

Historically the majority of structural engineers prefer doing design work, such as calculations and drawings, for extensions, lofts, basements, new houses or blocks of flats. However, it is far more difficult to find structural engineers who possess both a passion and expertise in the forensic, diagnostic and reporting sectors.

Whilst the training of structural engineers allows any chartered structural engineer to have a broad understanding of the stresses and strains in buildings and general associated defects, only those who specialise in conducting regular structural engineers’ reports are likely to have the appropriate experience to advise those buying and selling residential property. This expertise extends beyond technical knowledge but, crucially, the procedural aspects, such as dealing with mortgage lenders, valuation surveyors, insurance companies, estate agents and solicitors.

As with any other sector of business, there are subtle nuances associated with the preparation of reports within the residential buying and selling process. A report may be factually accurate, but it might not be realistic at the point of sale. For example, we find it all too common for some structural reports to recommend all manner of intrusive exploratory works associated with testing the soil, drains and tree roots, together with monitoring cracks for many months and often up to a year – all clearly inappropriate at the point of sale.

Most chartered structural engineers’ reports are required at the eleventh hour during the purchasing process, as a second opinion is required following general practice surveyors’ Level 2 or Level 3 surveys. The chartered surveyor has normally formed their own opinion on the severity of a structural concern but they require a prompt and practical second opinion to help support the buying process and before mortgages can be granted and contracts exchanged.

The buying and selling process requires a clear, straightforward, and decisive report that can be easily understood by anyone. It should avoid complex structural calculations and engineering jargon, presenting information in plain, everyday language.

How to find the right Chartered Structural Engineer

When selecting the right chartered structural engineer, begin by ensuring the professional has the all-important qualifications, indicated by the post-nominal letters ‘BSc CEng MIStructE’. These credentials confirm that the structural engineer has met rigorous standards and is fully and appropriately qualified. Be aware, the qualification must apply to the individual professional carrying out the report and not to the overall company. It is vital that the advice is obtained from a chartered structural engineer and not from a less experienced junior assistant.

Those structural engineers most likely to be able to advise will be located firmly at the smaller, more specialised, end of the profession. They should have significant residential experience rather than experience with commercial buildings. More particularly, they should possess long-term familiarity with existing building stock within the area of interest rather than the design of new buildings, which is a completely different discipline.

Years of helping builders take old houses apart provide invaluable experience regarding how residential property is constructed and what lies beneath the surface of wall plaster, render, and roof tiles. Genuinely useful and pragmatic advice comes from a practical and deep understanding of existing buildings and not from modern day calculations and drawings associated with new buildings.

The relevant chartered structural engineer should be able to demonstrate a proven track record of producing similar reports for buyers and sellers, and should be able to provide client testimonials that attest to their service over the long term.

In addition, a well-organised chartered structural engineer will have specific terms of engagement associated with the delivery of their advisory and reporting services. This information should be made available to you well in advance of the survey date so that you are clear about the level of service to be provided. There is normally a range of types of report available, with differing fees, which the structural engineer should offer you so that you can make an informed choice. They should offer more than just the basic service; they should also present a more comprehensive option that may better meet your specific needs and provide greater peace of mind.

The chartered structural engineer should be able to agree a clear timeframe for responding to your enquiry, both in terms of preparation, and engagement and professional fees. They should also be able to give you a firm date for the visit and, most importantly, a total timeframe for the production of the all-important written report following their inspection.

A personable structural engineer will normally contact you by telephone following the visit to let you know how they have got on, so that the formal report is simply confirmation of their resulting advice to you. This is particularly helpful as the report will likely contain some technical terms. However, it remains important that they communicate clarity and minimise jargon to ensure the report is easy for you to understand.

The professional fees charged by structural engineers vary enormously depending on a number of factors including, their level of technical expertise, geographical location, and office overheads. There are also less tangible, but normal, commercial considerations such as the engineer’s professional indemnity insurance costs, other overheads, and their mechanism for charging fees. Occasionally a chartered structural engineer will base their fees and advise on a ‘time spent’ basis, but it is far more common for fees to be based on a lump sum arrangement so that all parties know where they stand. These are normally paid in advance, in line with the practice of chartered surveyors and banks.

Another consideration when selecting a qualified structural engineer is their familiarity with the particular housing stock and the key geological conditions relevant to the property’s location. It is also essential that they are familiar with the ground conditions when reporting on matters of settlement, subsidence and cracking damage, and in particular, when weighing up future subsidence risks.

A further consideration is if the client is likely to require ongoing advice beyond the first stage of reporting. This is particularly appropriate to vendors rather than buyers where they may, for example, be seeking advice on removing a loadbearing wall which may require calculations and drawings. Alternatively, if a detailed specification is needed or the supervision or inspection of building work is required, then only some firms of a certain size are able to offer this particular service. It is essential that this is made clear at the time of the client’s enquiry in order to manage their expectation so that they are not left in the lurch and need to find an alternative structural engineer halfway through the process.

Where to find the right Chartered Structural Engineer

When looking for a Chartered Structural Engineer, the most suitable firms are those recognised within the industry, rather than being prominently featured on paid website directories or pay-per-click advertisements. Typically, a knowledgeable professional such as your RICS Chartered Surveyor, who may have conducted your pre-purchase survey, can recommend a reputable structural engineer. Structural Engineers Reports often result from the recommendations of such surveyors.

Other useful sources of recommendations are your Solicitor or Estate Agent, who are deeply involved in the property process and likely know experienced local structural engineers.

If personal recommendations are insufficient, consider these two online search tips.

First, use the Institution of Structural Engineers’ search portal at findanengineer.com. This platform lists firms employing Chartered Structural Engineers, members of The Institution of Structural Engineers with the all important C Eng MIStructE qualification for Structural Engineers Reports required by most clients, lenders, and insurers.

Then choose the “Domestic; Surveying, Inspection, and Appraisal” category and use the pull-down menus to enter your London Borough or Town, such as United Kingdom/England/London/Merton.

Alternatively, do a web search for Chartered Structural Engineers specialising in domestic house reports or something similar. Check the credentials of these firms, together with their Google reviews, and speak with a representative about their experience, scope of services, and professional fees.

Concluding comments

In summary, when selecting a chartered structural engineer for reports and advisory work, there is a wide range of factors to be considered. The most important criteria are the expertise, competence, and experience of the professional together with the timeliness of the reporting service if you are a buyer with time pressures.

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Why do we all find much more movement and cracking specifically within the rear addition/projection compared to the front elevation, when considering mid terraced Victorian houses in London.

Any discrepancy between the amount of trees to front and rear can be ignored. Bay window projections are also excluded for discussion purposes.

The answer

The answer, prior to the explanation, is simply due to the relative lack of lateral restraint or buttressing of a rear addition compared to the continuous nature of the front elevation.

The explanation

To be read with the sketch Sk13 (a to d) below.

Diagram (a) shows a front elevation of four houses with the subject house coloured green.

Diagram (b) shows its plan form with continuity of the front elevation, with rear projection adjoining its neighbour to the right. The letter “J” denotes a joint between abutting walls, often where the party walls abut the front elevation, where the flank wall abuts the main rear wall and also often within the party wall where there is sometimes a joint or gap (Used for the old lead pipes for the water tank) but more commonly poor bonding of brickwork.

Diagram (c) shows a simple isometric demonstrating how the rear projection is free to tilt away from the main house and to a lesser extent away from its neighbour.

Diagram (d) replicates the previous question 1 for ease of reference where we explored the subsidence to the right hand side of the frontage with tapered diagonal cracks emanating from the free edge at the top flank corner and gradually propagating downwards to the pivot point near the front door.

Overview

If we step back from our detailed site surveys and Structural Engineers reports for a moment we can consider the structural “form” of different building types whether they are framed steel or concrete office blocks or, in this instance, very simple plain brickwork housing stock.

In their purest forms, houses are a series of boxes.When a terrace is formed, with one long elevation at the front and a number of rear projections at the back, we have a number of boxes but connected together to become stronger, at least as far as the front and main rear elevation are concerned.

The rear projections are normally pairs of boxes twinned with the neighbour in respect of its rear wall but remain a single box structure with regard to the flank wall.

Unfortunately, whilst a box structure is normally strong when the corners are rigidly connected, many Victorian houses have gaps or joints between abutting walls, and in particular with regards to the rear projections. This is because they were invariably built by different teams of people, a number of weeks after the main house was built and with little regard, in many instances, to connecting the two structures together.

Whereas, the front elevation of a mid terraced house is sandwiched in between other houses and forms part of a much longer and continuous wall structure, a rear projection. As the name infers it is a “projection” from the general building line and, therefore, lacks any lateral support by comparison.

The enclosed diagram indicates the compressive or lateral restraint of this elevation if it tries to tilt within its vertical plane as per the detached or end of terrace house, as explained in a previous article.

The plan diagram (b) and simple isometric diagram (c) shows how the flank wall of the rear projection and the rear wall, to a lesser extent, is free to rotate when subsidence of the ground occurs. NB subsidence magnitude is not uniform and occurs greatest nearer a tree.

In Quiz question 1 we explored how unrestrained walls, such as those of a detached or an end of terrace, tend to tilt and rotate as a consequence of foundation movement. See diagram (d) on SK13. The rear projection flank walls behave in the same way, as do bay window projections.

There are multiple reasons why a rear projection might subside, many mentioned in the various comments thank you. It is the shape and form which allows the rear addition to move, assuming all other factors are broadly equal.

By way of general observations the most common causes of rear addition subsidence (Modern day movement), compared to the front elevation, tend to be;

1. Located nearest mature and or more frequent trees and large shrubs.
2. Drainage passes parallel and often below flank wall footings.
3. Lack of bonding or tying-in to main rear wall or house party wall.
4. Shallower foundations than the main house, particularly when the cellar is under the hallway and stairs.

Other common defects found within rear projections but which do not particularly contribute to the foundation movement discussion include;

• Poor brickwork quality generally, compared with frontage
• Poor bonding with the use of snapped headers.
• Built in timbers including backing lintels to brick arches
• Lack of lateral restraint perpendicular to floor span.
• Overloading of first floor joists from heady partition loads and roof props.
• Mono pitched roofs often undersized. Often no loft access to assess.

Watch this space and on Linkedin for further quiz questions and discussions.

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Simon Pole BSc C Eng FIStructE MICE MRICS MAE

Simon is well known within the profession and has regularly provided training courses and lectured at The Institution Of Structural Engineers and the Party Wall Society together at numerous firms of Chartered Surveyors.

SERL Pole Structural Engineers Reports is a specialist company advising all manner of buyers, sellers and owners of residential property in London and the surrounding area.

This article, together with several further blogs to be published shortly, is an introduction to cracks in buildings, explaining in simple terms what they are, why they occur, whether they are something to worry about and what to do about them.

This article introduces the topic and covers:

• What is a crack?
• Why do we worry about cracks.

Introduction to cracks

Cracks are, understandably, a very emotive subject. Our property is usually our largest financial investment and anything which appears to damage it, can be a worry. The very mention of cracks conjures up images of something breaking or not being strong enough and, in rare cases, be a significant problem involving health and safety. Normally cracks are just a nuisance that can be dealt with quite routinely. Whilst repairs are often routine, the prospect of them reoccurring is often high and reducing the risk of them reoccurring or eliminating such risks in the future is far more difficult. A structural Engineer can help you appraise this risk. See later article on Building Insurance issues.

In most scenarios, cracks are more routinely repaired, a bit like a dent in the bodywork of a car, and can normally be lived with. This article provides clarity on the subject and offers some reassurance.

1. What is a crack?

In simple terms cracks are the “pulling apart” of brittle materials, whether bricks, plaster or render.

Most domestic property is built using clay bricks, which are strong when compressed but relatively weak when pulled apart or “in tension”.

Cracks generally occur when there is a change of circumstance or environment either to the wall surface itself, for example temperature or moisture changes, or more significantly when there are changes to the volume of the supporting subsoil:

• • Changes in moisture and temperature result in minor effects such as normal plaster or render cracks.
  • Where there has been recent building work there may be slight changes to weight loading stresses.
  • When all other factors are stable but there are changes in ground conditions, for example, the drying out of London Clay soil due to trees sucking moisture from the soil, can cause varying degrees of cracking. See later articles.

2. Why do we worry about cracks in our homes?

Whether buying or selling a home, cracks can be a major issue, and up to 75% of our Structural Engineers Reports for properties in London and the surrounding area, arise at the point of sale for this reason. The remaining 25% tend to be for existing homeowners worried about cracks and whether they should notify their Insurance Company.

There are all manner of reasons to be concerned about matters of movement and cracking, whether buying or selling, as a Surveyor of property responsible for mortgage valuation or as a bank, Building Society or an Insurance company considering household insurance risks. Solicitors and Estate Agents advising the various parties will also want to understand the risks involved.

Cracks of any sort tend to be a warning for what could be a problem. They may not necessarily an issue but their sudden appearance and widening over time or reoccurring in newly decorated walls may indicate a problem. It is the not knowing which often causes concern and the need for our advice and reporting.

Other professions will not mind me saying that it is only when a Chartered Structural Engineer inspects and reports on cracking and movement that the client tends to be completely reassured. The training of other property professionals might include a general awareness of cracking and movement but their many areas of expertise covers so many other aspects that they cannot be expected to be experts in each particular specialism. Much like a GP Doctor who will provide an initial opinion, then refer the patient to a specialist for particular aches and pains within those particular organs, muscles and tendons etc.

For the above reasons it is increasingly common for Surveyors and other property professionals to recommend a structural engineers report.

More detailed articles will shortly appear to assist each property profession but the following points are the key reasons why each party to a typical property sale might have cause for concern:

• • • The homeowner

You have an immediate vested interest and therefore need to be reassured that your property is safe and strong, whether simple repairs are required or more detailed investigations and repairs may be required. You could also need advice before notifying your insurance company, either in general or for concern of non disclosure, which may jeopardise a future insurance claim, increased premium or even removal of subsidence cover. Some Insurance companies ask for a structural Engineers Report to accompany a claim in the first place.

• • • Selling your Home

Discerning vendors and their selling Agent are more often obtaining a Structural Engineers Report at the commencement of marketing their property, either generally or because of a specific crack or structural defect which they have not repaired, which might concern a prospective buyer.

Providing a Structural Engineers Report pre sale can reassure potential buyers and provides transparency, which increases confidence for the buyer.

All too often we are asked to report for buyers at the eleventh hour, for example, prior to the exchange of contracts and the buyer becomes nervous quite unnecessarily.

• • • The buyer

Most Structural Engineers Reports stem from the General Survey (RICS level 2 or 3) link to RICS or during the Bank Surveyors mortgage valuation. Our report may, therefore, either be for the peace of mind of the buyer or might become a third party requirement. It is particularly important the Structural Engineers Report is prepared by a fully qualified, Chartered Structural Engineer (CEng MIStructE qualifications), since only they will normally have both the expertise and minimum qualifications expected by the Bank, Building Society or Insurance company. Note, a graduate Engineer or Associate Member of a Built environment profession is not a chartered Structural Engineer so do check this carefully to avoid the need for paying for two reports.

A good Structural Engineers Report should provide clear, jargon free advice indicating whether you are able to proceed with the purchase or not, and if any repairs might be involve together with an order of cost.

• • • The Estate Agent

A discerning Estate Agent will appreciate the benefits of an early Structural Engineers Report, to indicate anything serious and for the vendor to have a report they can show to prospective purchasers. This can avoid the last minute problems created by waiting to see whether the buyer or their Surveyor or solicitor calls for a last minute Structural report.

• • • Buyers Surveyor or valuation survey

The majority of Structural Engineers Reports stem from a general Survey of some sort, whether for the buyer or the lender. If they are via the mortgage or Insurance provider they will be essential. If they are for your own peace of mind but a strong recommendation by your GP Surveyor then of course most people will take this advice. It is important, however, to clarify with the Surveyor and specifically what the structural concerns are. For example, are they confined to one particular crack in a bay window, or are there general concerns for the entire property. Most firms of Engineers offer two distinct types of report with different price points; either a specific defect report only or a more general movement report.

• • • Buyers Solicitor

A discerning conveyance solicitor will strongly recommend obtaining various specialist reports or a Surveyors report. This might not be confined to cracks and movement but increasingly common is if there has been any structural alterations, walls or chimneybreasts removed etc without Local Authority Building Regulations consent. Note this is not the same as Town Planning or permitted Development rights.

• • • Buyers lender

The bank or Building Society will need to understand whether any structural issues raised by the Surveyor are serious. The context for this is financial risk generally but particularly in the unlikely event of a repossession and whether the property is easily resold.

If there are expensive structural repairs involved and a mortgage applicant is heavily dependent on a large mortgage with few savings, they might not be able to fund the repairs.

• • • Insurance Companies

Whether for a current owner or for new Insurance associated with a purchase and mortgage offer, Insurers play an important role which is often misunderstood.

For an owner, an Insurance company may receive notification of an insurance claim for repairs. For a buyer, the prospective Insurer will want to know whether there are any current problems with the property or whether there is pre-existing damage.

Insurers are only in the business of Insuring for certain repairs which are not covered by routine maintenance; for example, fire, flood or subsidence. They are not interested in general maintenance, routine repair or neglect. Crucially they only deal with essential repairs to subsidence damaged property, for example, and are not obliged to prevent similar damage from reoccurring in the future. They do not deal with defective design or workmanship issues by a builder or a designers’ shortfall. A more detailed article will follow.

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