Reasons for contacting Structural Engineers Reports Ltd (SERL)

A prospective buyer of a terraced property contacted us following a failed mortgage survey. The valuation surveyor was concerned about various cracks inside and out, together with a more general history of movement.

N.B. Although this report was for a buyer, some twenty per cent of our enquiries are from owners who are either concerned about their property generally or, alternatively, are about to market their property for sale and wish to have a report which they can share with prospective buyers.

Summary

N.B. We always provide a one-page, easy-to-read summary at the beginning of each report.

We are satisfied that the property remains strong and shows no signs of any modern day movement. The various cracks noted were all considered historic and entirely normal for a period property more than one hundred years old.

The structural significance of the cracking can be conveyed to you numerically on a scale of one to ten, where one is minor and ten is severe. In this regard we would rate the cracks in this property at about two to three out of ten.

N.B. We often use a medical analogy and would in this instance describe the property as requiring a proverbial paracetamol rather than open heart surgery, open heart surgery being analogous to major underpinning or strengthening works.

Once the repairs have been carried out we would consider the property to be a normal lending and insuring risk.

N.B. When assessing the risk we consider the geology, proximity of trees and drains, etc.

Brief

We confirm your recent instructions in conjunction with your intended purchase of the above family terraced house.

You explained that your mortgage survey has highlighted cracking of some concern and the bank requires a chartered structural engineer’s report before considering the mortgage application. We further understand that the cracking is widespread inside and out.

Given the bank’s requirements you will need our general report, known as a General Structural Inspection, on all the main loadbearing walls inside and out. We have agreed to provide guidance regarding costing for repairs and can provide the names of specialist repair contractors.

N.B. Less frequently we provide a more localised report, known as a Specific Structural Inspection, where concerns are very limited such as for example a single crack in a single bay window.

We trust we have interpreted your brief correctly but please contact us immediately if not.

N.B. A formal report would include more details and would refer to guidance notes provided to clients prior to receiving confirmation to proceed with our inspection so clients are quite clear what we do and what our deliverables comprise.

Description of Property and Geology

The property is a very standard mid-terrace family dwelling house on two floors plus loft conversion.

The construction appears to comprise normal solid brick external walls with suspended upper timber floors and roof framing. Elevations are all yellow stock brickwork. The architectural style is typical of early 1900s construction.

The house layout is traditional with primary rooms in the forward part of the house between party walls and secondary rooms within the narrower but original rear projection adjoining the right hand party wall. There are no modern day extensions or significant changes to original room layouts.

The property occupies a fairly level site. Our geological mapping records indicate London Clay subsoil. There is a large London plane tree close to the front left-hand side of the property within five metres. The tree is some fifteen metres tall. The drains appear to pass beneath the property from the rear towards the front. The house is in good order decoratively but has not been well maintained externally. An RICS Surveyor will comment on this in more detail.

Site Observations

Background context

Most of our detective work is carried out externally, since it is the bricks which form the main skeleton of the house, together with just one or two internal loadbearing walls.

We are mainly concerned with any cracks of a “structural Engineering nature” generally described as those cracks which occur on both sides of a loadbearing wall, eg inside and out in the case of an external wall AND where crack widths exceed about 3mm. This acknowledges that almost all building materials together with the soil mass, expands and contracts from time to time causing normal/ seasonal movements which do not compromise the structural integrity of a property.

In detail

The property exhibits a pronounced slope from right to left away from the front door and towards the bay window and the left-hand party wall.

There are various cracks dotted around the front elevation, typically between 1‑3 mm wide. In particular there is vertical cracking where the bay window abuts the main front elevation of the property, but all of this cracking is extremely discoloured and clearly of long standing.

Our internal observations note the decoration is old, at least ten or fifteen years in our estimation. Crucially there is no corresponding cracking internally, which confirms our suspicion that the cracking is long-standing and dormant.

The various brick arches over first floor bedroom windows are in good order.

The brickwork and pointing generally is also sound and your RICS surveyor will comment on all of this in more detail from a maintenance and general repair point of view.

At the rear of the property there is minor cracking where the front and rear halves of the property adjoin, which is very common. Internally there is an old crack in this location but this too shows no signs of any modern movement.

Internal floors slope from right to left, consistent with the cracking noted externally both within the front part of the house and the rear projection.

N.B. A formal report would include more detail that this.

Conclusions

See summary at the beginning of the report for an easy-to-read précis.

The property shows normal signs of historic settlement, from right to left, commensurate with the age of the property. We suspect that most of this early age settlement occurred soon after construction as the weight of the house squashed into the soft soil.

There has clearly been a minor to moderate dose of subsidence in the medium term past, approximately some twenty years ago, but crucially there is no sign of any ongoing movement.

The cracks require a routine resin repair and we estimate costs of approximately £3,000-£5,000 in this regard. We can recommend appropriate repair contractors for this work, which ideally should not be undertaken by a general builder. We recommend that you allow for testing of and minor repairs to the drains as part of your early planned maintenance.

Ideally the Local Authority would be encouraged to reduce the height of the tree, given that it is far too large for the urban environment.

It is obviously important that you maintain building insurance, and specifically subsidence cover, for any period house, particularly those on London Clay soils and fairly near large trees. It is however the nature of owning a period property that there is always a residual subsidence risk, but fortunately there is no sign of any recent movement here within the last twenty years or so.

Report signed by Chartered Structural Engineer.

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A prospective buyer commissioned an RICS survey which noted cracking to the front elevation inside and out including to the neighbouring property in Kew, Middlesex.

SERL Pole Structural Engineers Reports were contacted by the buyer who was seeking a reputable, independent, and highly experienced structural engineering firm practising in the Kew and West London area.

SERL Pole service offer

In response to the client’s requirements our qualified Chartered Structural Engineer recommended a Specific Structural Inspection Report.

There are two distinct types of structural engineers reports:

1) A localised, very specific and limited Structural Engineers Specific Structural Inspection Report (SSI).

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

We offered our localised Specific Inspection Report on this occasion as the Surveyor and buyer were not concerned about the rest of the property.

Our report

The property was a small Artisan two bed terraced cottage built in circa 1850. The local geology is alluvium due to the proximity to the river Thames, ie soft silts and sands over London Clay.

Findings

We found minor cracking internally but mainly lose plaster, therefore nothing to be concerned about. Externally there was some repointing and a very small crack to the neighbouring property.

Conclusions

We concluded the cracking was very minor although probably recent so we recommended the drains be tested and repaired if they were found to leak. These repairs should be less than £1,000.

We explained to the buyer that all period buildings “move” and crack a little from time to time but cracks of a few millimetres are not serious and do not undermine the structural integrity of a house. And simple repairs from time to time is all that is required.

Can we help you?

If you would like advice on any structural aspects of your property, our structural engineers’ are here to help you so please don’t hesitate to contact us.

Call us now on 020 8161 9900

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What is subsidence

Subsidence is the general term used to describe the downward movement of the ground and consequently a building resting upon it. More specifically we normally refer to the consequent cracking or structural damage that results.

Subsidence causes vary, depending on the type of soil, trees, drains and type of foundations beneath the property.

Most subsidence takes the form of minor cracking which is easily repaired from time to time but in extreme cases more significant repairs are required. Sometimes the cause of subsidence can be dealt with but on other occasions it cannot realistically be completely eliminated in the future. See later.

Why do we worry about subsidence?

The term subsidence can sound overly dramatic as it conveys images of buildings sinking into deep mining holes are sliding off steep cliff faces and generally causing catastrophic damage to our valuable homes.

In reality the above is rarely the case and particularly in London and the Home Counties where the geology is relatively uniform and well known, albeit prone to perhaps more frequent but minor damage in most instances.

The term subsidence has repercussions depending on circumstance and status eg whether owning, buying, selling or renting property and some of the main concerns for each of these status are as follows;

For homeowners

• Repair costs might be significant if the damage is not covered by Building Insurance and more specifically Subsidence Insurance. The normal policy excess is typically £ 1500.
• Making a Subsidence claim can be detrimental to future insurance premiums. In some instances, Insurance companies withdraw Insurance cover after making a claim which is very harsh.
• If minor cracking damage reoccurs regularly but does not exceed the policy excess, year on year repair costs can mount up and reoccurring cracking is a nuisance visually.
• In extreme cases internal repairs or strengthening such as underpinning or piling would necessitate moving out of the family home for many months whilst repairs are carried out. Whilst this is extremely rare in practice, the potential of this risk is what triggers a natural fear of subsidence.

For those selling

• Subsidence damage may prevent or restrict the sale of a property in terms of market appeal and potentially lower the sale price. See below.
• It is important to obtain professional advice from a Chartered Structural Engineer prior to sale, which might be shared with a prospective buyer, in order to smooth the sale process.

For buyers

• Many buyers will simply be put off buying a property with a current subsidence problem, for fear of costs of repairs and disruption to day to day living.
• It is difficult to obtain a mortgage, and Buildings Insurance, against a property with a current or ongoing subsidence problem even if the damage is minor, for fear of it becoming worse and expensive to resolve.
• A structural engineer’s report is almost bound to be required for any property showing recent signs of cracking, which might indicate a current or ongoing subsidence problem.

Estate Agent’s advice note

We always encourage Agents to recommend that a vendor obtains a Structural Engineers Report from a professional structural engineer when there are obvious cracks and signs of subsidence or historic settlement cracking. This report will inform the owners repairing options pre-marketing for sale, or alternatively, to share the report with prospective buyers on an open book basis so they can be informed at the earliest opportunity. This avoids wasted time and money later and can avoid disappointment all round.

Surveyor’s Reports

Depending on the type of RICS report and on the experience and knowledge of the surveyor, it is common for the general practice surveyor to refer matters of significant structural cracking to a Chartered Structural Engineer and they will recommend a report by such an expert.

A brief description of subsidence

Subsidence is the general term used for “sinking” of the soil and the consequent movement and cracking of the building on that sinking soil mass. Whilst it might sound rather dramatic, the reality is that in most cases that amount of subsidence is measured in a few millimetres rather than centimetres or inches so damage is normally fairly modest structurally.

Subsidence causes vary, depending on many factors as mentioned above but in 90% of cases in London and the Home Counties it is usually when a period house has shallow foundations resting on a shrinkable clay subsoil AND with medium to large trees nearby. There are exceptions however, which will be discussed in more detail in a subsequent paper.

A clay soil is a bit like a “blu tack” or plasticine and is mouldable by hand so is not very strong compared with bedrock, sands or gravels. Specifically, the clay comprises a large volume of tiny water molecules and it is the varying water content from one season to the next, or when sucked dry by tree roots, that causes a reduction in volume of that soil mass. This results in a downward movement of the soil together with that part of the building resting upon it.

In loose granular soils like sand, silts and fine gravel, if nearby drains are broken and fractured, the soil can fall into the drain pipes and be washed away, causing weaknesses in the soil beneath the foundations; a further but less common cause of subsidence.

Subsidence occurs regardless of any weight loading. For example, the ground under a garden path or lightweight conservatory might subside in periods of drought.

Mining subsidence and underground water course erosion of chalk and limestone rock, found elsewhere in the UK, is very unusual in the Home Counties due to the differing geology and is not dealt with in this article.

Settlement versus Subsidence

Subsidence is not the same as settlement and the distinction is very important.

Briefly, subsidence occurs when the soil mass below a house moves downwards of its own accord eg in dry summers, whereas settlement only occurs when weight loading is applied and squashes the soil downwards eg when building an extension or raising a house higher.

Settlement commonly occurred in most pre Second World War housing because foundation design was not understood and whilst many house were and are still very robust above ground, they have little or no foundations as we would know then today.

As a general rule of thumb most foundations in homes built before 1920 were typically the most shallow at some 20 to 40 cm below ground level. Post 1920s until the 1960s many house were founded at about 60cm deep

Only after the drought of 1976 did foundations routinely extend to 1m below ground and deeper in some instances, as the construction industry learnt of the dangers of tree roots causing subsidence.

In extreme cases when building near very large oak or poplar trees, new foundations were on occasions built to 2.5m deep or alternatively are now commonly supported on concrete stilts called piles instead, which extend much deeper into the soil.

Settlement takes place fairly immediately on granular soils like sand and gravel, usually within a year or so, and within the first five years or so on clay soils. For period houses, settlement is therefore by definition historic.

Settlement only rarely occurs in modern extensions and new houses due to the demands of modern building Regulations and design office Eurocodes used by Structural Engineering designers for their calculations of beams and foundation sizes.

We do see some settlement in poorly constructed ground bearing slabs for extensions when the ground is not sufficiently well compacted.

All this explains the importance of obtaining proper “design” advice from a structural engineer together with achieving Building Regulations Approval, including the completion certificate when works are completed.

What you should do if you think you have subsidence

There are two general options but these might be influenced by a number of factors mentioned further below;

1. Notify your insurance company and hope they deal with it professionally.
2. Obtain an independent report from a Chartered Structural Engineer

Historically subsidence claims were dealt with via a panel of independent Structural Engineers overseen by Loss Adjusters on behalf of Insurance Companies. This has all changed and almost all cases are now dealt with “in house” by Insurance Companies and “term contractors” with mixed success as far as the homeowner is concerned.

As a house owner your probably have subsidence insurance as part of your building insurance policy. If you are a leaseholder, the insurance is probably via the freeholder.

Most insurance policies have an excess to pay upwards of £1500.

If you start with your insurance company you will not incur any initial costs but may or may not receive the correct technical advice as a Chartered Structural Engineer will not be involved in most instances.

Alternatively, you might initially seek the advice of an independent Chartered Structural Engineer with professional fee costs of the order of £1500, paid by yourself.

Some insurance companies now ask for a structural inspection report from a Chartered Structural Engineer before they will visit or deal with a claim in order to establish whether there is likely to be a subsidence case to deal with or not.

Note not any damage or any cracks or movement are automatically dealt with by insurance companies. They do not deal with either pre-existing, pre-policy inception date, damage nor maintenance and wear and tear issues.

You are obliged to notify your insurers if your property suffers significant damage but you may or may not elect to make a formal claim in order for them to consider covering repair costs. Some people would rather fund modest repair costs and maintain a “ clean” insurance policy much like a “no claims” car insurance policy. This is particularly useful if you are intending to sell the property in the near future as a prospective buyer might be put off by news of recent insurance claims. In our experience solicitors advising buyers are very nervous about recent insurance claims.

A good independent Chartered Structural Engineers report will make clear whether you have a current subsidence issue or not and what order of costs might be involved in dealing with repairs. This will hopefully help inform you whether to make a formal insurance claim or not.

What insurance claims and repairs do NOT do, however, is improve the property nor prevent similar damage occurring again in the future – insurance is about repairs rather than improvement. For example, the repair of cracks does not mean they will not reoccur one day. If, however, an offending tree can be easily removed or reduced in size this will reduce the risk of a future re-occurrence at marginal cost.

In the past properties were frequently underpinned, deeper foundations were created by pouring concrete under the existing foundations, as part of a repair but this rarely occurs today as it is deemed an improvement to the house and is not often needed solely to repair damaged foundations. Only in very rare circumstances where a very large tree on neighbouring land or with a tree protection order placed upon it and where year on year recurrent damage is eminently foreseeable, might underpinning be considered as part of a repair.

Normal repairs

Without going into detail now, in the majority of cases, cracks and damaged decoration are easily repaired and rooms redecorated. Routine tree pruning or pollarding together with any drainage repairs are commonplace.

Cracks masonry must be repaired properly with either resin (for fine cracks) or Cementitious grout for larger cracks. In instances where   a wall has been substantially weakened and would benefit from additional tensile strength, some cracks are reinforced by stainless steel helibar rod reinforcement but only when specified by the structural engineer.

Repairs must be carried out by specialist repair contractors and approved helibar installers not general tradesman or builders ideally.

Most crack repairs are relatively inexpensive, certainly in comparison with very high property prices. Normally, one or two cracks can be repaired for a £1,000 to £2,000 and some 20 or 30 cracks dotted around a large house could be repaired for less than £20,000 excluding redecorations, so the figures are by no means astronomical. Smaller cracks can be repaired within the normal insurance policy excess, typically £1500 and whilst insurance companies should always be notified of damage, there is often no financial reason to make an Insurance claim.

Reflections

We are frequently surprised that lending institutions are so risk averse, at the slightest mention of subsidence, given how rare expensive underpinning is and how marginal most crack repairs are.

Most of us know, anecdotally, that many of London’s older housing stock has had some sort of minor subsidence in the past and either an insurance claim is on record or there are a few cracks in need of repair from time to time.

Unfortunately there is a big disconnect between the perception of subsidence and what it really means and this creates significant tensions during the buying and selling process which is related more to public perception and lending or insuring implications rather than issues of structural engineering.

Our role as Chartered Structural Engineers in this arena is therefore as much about human perceptions and expectations as it is about structural engineering. A good Structural Engineer can hopefully help you with both.

Conclusions

This article has introduced the broad subject of subsidence and settlement and what it means for you whether owning, buying or selling property. It provides guidance on what you might do if you think you have subsidence and gives food for thought regarding the issues surrounding selling a property at this time.

A future article will shortly provide some information and guidance on what subsidence cracks might look like and when you might become concerned.

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An introduction to cracks

Many people often have concerns about cracks present in their homes or those they plan to purchase. Whether the cracks are small or large, there is often uncertainty regarding their severity. This second article in the series explains “cracking” in more detail and provides guidance on when it is necessary to be concerned. Additionally, it aims to reassure readers that not all cracks are indicative of serious issues.

A background to cracks

It is only natural that cracks in a property can cause concern. Whist many cracks turn out not to be serious, those which become a genuine concern, can start off as small, minor cracks. Cracks in buildings can also cause concerns among surveyors, lenders, and insurers, which can result in challenges when buying and selling property and occasionally impact property prices.

Firstly, it’s important to say that most building materials occasionally crack. At the smaller end of the scale they shrink and expand due to changes in the environment. Those changes might be due to stresses and strains, which can lead to more significant implications, or just changes in moisture or temperature levels from one season to the next. These are less problematic. The more brittle the material, the more likely it is to be prone to cracking when exposed to any changes in its environment. This is why modern plaster and some external renders crack so easily due to their brittleness.

The most common building materials seen with cracks are either internal plaster or external brickwork and cement renders.

Most people notice cracks inside their homes first, as they are constantly exposed to this environment. And cracks on the exterior may also be quite noticeable, especially those near the front door. However, cracks in less obvious areas outside, such as the sides of the house or hidden behind garden shrubs, often go unnoticed by many homeowners. We often point these out during our surveys revealing that the owner were unaware of them.

Some small cracks might be recent but are continuing to widen so could be a problem in the future, whereas a larger crack might be very old and dormant, therefore less of a concern.

We need to differentiate between cracks which are a personal concern of the homeowner, and those which present a structural concern. The two are quite different and so Engineers and Surveyors need to appreciate this point. Cracks which worry many homeowners, and indeed those Surveyors associated with mortgage Surveys, may only range from a hairline width to perhaps 2 or 3mm wide.

In contrast, a Chartered Structural Engineer and the building industry does not, in general, become concerned until a crack widths is typically 5mm wide AND is becoming progressively wider. That said, as Structural Engineers we understand the concerns of owners and buyers and the practical issues associated with obtaining mortgages and Building Insurance.

A good Structural Engineer will appraise the implications of any cracks and present the report in a way that is readily understood by the public and crucially reflect both their concerns and the practical implications for obtaining mortgages and building Subsidence Insurance.

When construction projects are in progress and in the event, neighbouring buildings are damaged, the Party Wall Etc Act 1996 usually deals with the resulting damage and there is time to investigate and propose alternative solutions. In contrast, at the point of sale, Structural Engineers do not have the luxury of time to investigate, dig holes and monitor cracks, so a more decisive conclusion must be reached to assist the buying process.

The much quoted Burland Scale which categorises cracks together with the British Research Establishment Document number 251 1995, will be the subject of a future article.

Minor cracking

The following might help you when looking at cracks that are between a hairline to 3mm range.

Cracks which are not usually a problem

• A crack that is located in a non load-bearing structure, such as a lightweight partition or in a piece of wooden joinery. Be aware that some timber stud walls can be load-bearing.
• An internal crack that occurs at a junction between abutting a wall or between a wall and the ceiling.
• A crack which only occurs internally, within an external wall, but does not occur in about same location externally.
• A very old, dark and dusty crack, which occurs in a structural wall, inside and outside in the same location but shows no signs of ongoing movement. Simple correct resin repairs may be the solution to keep the property strong and robust. A further article regarding crack repairs will appear soon. 

But what about more serious cracks?

Cracks which are either larger, more than 5mm, and smaller cracks of a particular type which progressively become larger, may be a cause for concern.

As we have said previously, there is a distinction between cracks which are of personal concern for the homeowner compared to cracks which are of a structural concern and where major repair might be required. A homeowner who isn’t planning on moving may well be able to take longterm pragmatic action towards the cracks which occur in their home, providing they receive the correct structural advice and are subsequently reassured. In contrast, even small but progressive cracks can cause disruption to the buying and selling process and so it’s important to consider the position of the reader.

Identifying more serious cracks

In general terms, cracks which are of some structural concern usually include the following:

• Recent cracks in external walls, throughout the thickness of the wall, appearing both inside and out and seem to be getting wider year on year. In London and the Home Counties, London Clay and trees combined tend to cause most subsidence cracks. A future article will look at geology, trees and the general causes of subsidence.
• Diagonal AND tapered cracks in external walls, inside and out. These types of cracks tend to propagate from the top of a building and move downwards, as a result of what we call rotational movement of a building. This is perhaps counterintuitive when considering foundation movement and subsidence as many people might reasonably look for cracks close to the ground first! Subsidence and crack pattern will be explained in a future article.
• Cracks wider than 2 or 3mm may concern a pre-purchase surveyor and impact the sale transaction process even though the damage is slight in structural engineering terms.
• Cracks wider than 5mm start to become more serious to the structural engineer and whilst safety is not an issue, it becomes more important to establish causation and properly engineered repair solutions.
• Cracks larger than about 20 to 25mm can start to impact structural performance and possibly safety so must be taken very seriously.

Conclusions

Cracks can elicit strong emotions in property owners, buyers and lenders, and Insuring Institutions.

The reasons for worrying about cracks are understood by an experienced and expert Chartered Structural Engineer, who can normally provide reassurance and clear guidance for action and repairs.

In general, Structural Engineers and the building Industry tend not to worry about smaller scale cracks as they rarely have an impact on the structural performance of a building and can usually be repaired easily and inexpensively, much like a dent in the bodywork of a car. Preventing cracks from reoccurring, however, is often more challenging, similar to preventing dents on a car.

In summary, cracking in general tends to worry many people perhaps unnecessarily, particularly during the stressful period of buying and selling property.

This article has given advice for what to look for in cracks, either minor or more serious, but must be regarded as very general advice since each and every property is different.

A Chartered Structural Engineer with specialist knowledge on cracks in residential buildings is the most appropriate property consultant to advise you on such matters.

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