BASE - Best Answer Subsidence Engineering Ltd

BASE was set up in 2011 because we felt there were shortcomings in what has become the mainstream approach to investigating subsidence damage. In particular, there seems to have been a gradual shift in recent years towards a uniform approach to all subsidence claims, which is tailored towards the cases of minor movement that form the majority. As a result, in the minority of complex claims involving potentially large movements, the investigations can be inadequate and, because third party tree owners are less likely to co-operate when approached with incomplete or poor evidence, this results in delay or avoidable underpinning.

The BASE approach seeks to "sort the wheat from the chaff" - serious cases of subsidence, where underpinning is likely to be needed unless the cause of the movement can be addressed quickly, are identified at day one. Subsequent investigations are then tailored to provide the evidence needed to present to third party tree owners or, in the case of protected trees, to the Local Authority. This almost always includes precise level monitoring in addition to the crack monitoring carried out by most investigators.

As well as confirming the initial diagnosis, the level monitoring results provide a rational basis for identifying which trees are implicated and whether these need to be removed or simply reduced.

The result is reduced claim duration and, in many cases, reduced cost to the insurer because expensive and disruptive underpinning operations can be avoided - but only in circumstances where the cause of the movement has been eliminated.

The BASE philosophy is built around the guidance provided by the Building Research Establishment (BRE) and a keystone to our approach is keeping the home owner informed at all stages of the claim process.

BASE offers a full range of consultancy services in relation to subsidence damaged properties, including the following:

Initial inspection

The initial inspection needs to be carried out by a suitably-qualified Engineer who can assess the cause and the severity of the problem and advise the homeowner accordingly. Cases of potentially serious movement that may result in underpinning (unless the cause of the movement is eliminated quickly) need to be sorted from cases of minor seasonal movement and cases where the most likely cause of the damage is something other than subsidence.

Engineers Report

The Engineer's Report records key information such as location and nature of cracks, local geology, position of trees, etc, identifies the most likely cause of the damage, and makes recommendations for further investigations and remedial options. The report will also consider what damage is likely to be covered by the Building's insurance: subject to certain exclusions, most policies cover damage caused by foundation movement (i.e. subsidence or heave) and damage caused by an Escape of Water, but other causes such as general deterioration of the building materials are generally excluded. Insurance cover may also depend on other considerations such as the adequacy of the sum insured and whether some of the damage existed when the policy was taken out; these are issues that are normally addressed by the insurer's appointed loss adjuster.

Specifying and arranging soil investigations

Most cases of subsidence will require a soil investigation to confirm what is happening to the foundations. However, the scope of the investigation required will vary according to the suspected cause and the severity of the damage. Where the cause is a tree belonging to the property, a single trial pit and hand-augered borehole will often provide all the information that is required. Where there are several trees within influencing distance, some of which belong to a third party or are covered by TPOs, a more detailed assessment will be needed to (a) provide evidence to the third party tree owner and (b) determine that it is safe to remove the trees.

Specialist advice on technically difficult claims

Large trees can cause what is known as a persistent moisture deficit, which means that the soil will swell following removal. Where the extent of this swelling (or heave potential) is large, there may be an unacceptable risk of causing further damage over a period of years or even decades. Heave potential can be estimated from the results of soil tests, although careful and skilful interpretation is required because some testing can yield spurious results, There is also a range of opinion within the industry as to how much heave constitutes an unacceptable risk. The simple truth is that each case has to be judged on its own merits.

Specifying and interpreting monitoring

Precise level monitoring is the only technique that can be used to quantify the extent and scale of the foundation movements to a subsidence-damaged property. Despite the obvious advantages of measurements of this kind, many investigators / insurers tend to favour the cheaper alternative of crack monitoring. Geo-Serv offer an unrivalled level monitoring service nationally at competitive prices.

Because all properties founded on clay soil will move up and down slightly over the course of the year due to shrinkage and swelling in the surface soil, level monitoring requires careful interpretation. Ideally, the results for an individual property need to be considered in the context of what is happening to other properties in the same area due to the prevailing weather conditions. Because they undertake thousands of monitoring surveys each year, Geo-Serv has access to a unique database of foundation movement.

Dealing with Local Authorities and third party tree owners

Where it is suspected that street trees or neighbours' trees have contributed to the damage, it is critically important that the right evidence is collected at an early stage to avoid delaying the claim unnecessarily. Understandably most third party tree owners will be reluctant to remove their trees unless they are sure (a) that the trees have contributed to the damage and (b) that removal, rather than pruning, is essential. In such circumstances, it is not unreasonable for the third party to ask for "proof", which is likely to include soil test results, root identification and monitoring. In practice, crack monitoring can be ambiguous and open to interpretation whereas the results of level monitoring will generally provide a clear picture of which part of the property is moving and by how much. Accordingly, it is difficult for a third party tree owner to refute good quality level monitoring data, and the chances of cooperation at an early stage are much greater.

Conservation Area and TPO Applications

Many privately owned trees are subject to Tree Preservation Orders or TPOs which makes it unlawful to remove or prune the tree without submitting a formal Application to the Local Authority. Where a tree is implicated in subsidence damage, the Local Authority will demand certain levels of evidence before accepting an Application. In particular, it is mandatory to provide the results of level monitoring over an appropriate period or to explain why these results are not available.

If you live in a Conservation Area it is necessary to notify the Local Authority before removing or cutting back a tree, even if it is implicated in damage to your property or a neighbour's property. If the Local Authority has any reservations regarding the necessity of the work that is being proposed, they can apply a TPO to the tree, which means that the tree owner has to submit a formal Application accompanied by level monitoring results. Unless the possibility of the TPO is recognised at the outset of the claim, this will inevitably result in a long delay while the monitoring is undertaken.

Specifying repairs and underpinning

Generally underpinning will be required only where it has not been possible to mitigate the cause of the subsidence (e.g. to remove an implicated tree or repair a defective drain). A range of options exist from localised mass-concrete (traditional) underpinning to a piled-raft under the whole property. Selecting the right solution depends on the soil conditions and the extent of the movement see Has Your House Got Cracks? for further details.

Whether underpinning is carried out or not, structural repairs will be required to reinstate the integrity of damaged walls and the affected area will require decoration. The cost of repairing any damage reasonably attributable to the subsidence is normally covered by your Buildings' Policy, subject to a policy excess. Traditionally the Schedule of Repairs was drawn up by the Engineer for approval by the home owner and the loss adjuster, before tendering to a number of contractors. Under the project-managed system operated by many major insurers, the loss adjuster draws up the Schedule of Repairs and appoints the contractor from a panel approved by the insurer.

Project management and contract administration

Where the Schedule of Repairs has been drawn up by the homeowner's Engineer, the work is normally completed by a general builder or repair specialist working under an appropriate contract, such as the JCT Minor Works Contract. The insurer will usually not be a party to the contract, but will agree to fund the work and will ask the homeowner to sign a mandate allowing the insurer to pay the contractor directly.

The Engineer acts as the Contract Administrator which means that he has to approve payments to the contractor as well as making sure that the work progresses to plan. Any problems that are encountered are dealt with as "contract variations" and there may be a penalty clause for a contractor who does not complete the work diligently.

Party Wall matters

If the work involves repairs to the party wall or excavation within 3 m of a neighbouring property (6 m in some circumstances), it will be necessary to issue the owners of the Adjoining Property with a notice under the Party Wall, etc Act, 1996. The notice can be issued by the Engineer or Loss Adjuster and the Adjoining Owner can either agree to your Engineer/Adjuster acting as the Party Wall Surveyor or can dissent and ask for their own Party Wall Surveyor to be appointed. Where the work is being carried out as part of a valid subsidence claim, your insurance policy will normally cover the cost of these professional fees.

In complex cases, involving underpinning of the party wall for example, the Adjoining Owner's Party Wall surveyor may want to employ a specialist Engineer to advise on the implications for their client's property. Geo-Serv / BASE act as Party Wall surveyors and specialist engineers.

Trouble-shooting, mediation and dispute resolution

It would be nave to assume that all subsidence claims run smoothly without arguments arising over issues such as causation, appropriate remedial measures, entitlement under the terms of the policy, and delays. A common complaint that we come across is home owners who feel that they are not being fully informed as to the cause of the damage and what needs to done to fix it. A recurrence of damage after repairs have been carried out, can also result in a home owner losing confidence with the investigator.

It is in everyone's best interest to avoid an impasse arising and Geo-Serv / BASE has considerable experience in dealing with complaint situations for the home owner, the insurer and the Financial Ombudsman (FOS).

Where the problem is a technical one, a fresh pair of eyes can often help resolve misunderstandings and identify any further investigations that are needed to clarify the cause and/or appropriate remedial measures.

Where the problem is more one of personalities or loss of confidence, Geo-Serv / BASE can, with the approval of the insurer, take over the running of the claim and provide an experienced Engineer to see the claim through to a prompt conclusion.

Expert Witness Reports

Very occasionally, it may be necessary to pursue legal action to recover costs from a third party that has caused subsidence damage through negligence or nuisance for example, a Local Authority that has failed to maintain its trees adequately. In most cases, the recovery is sought by the insurer on a subrogated basis. However, where successful, the homeowner will be entitled to recover a proportion of their policy excess and uninsured losses.

Legal action is governed by the Civil Procedure Rules (CPR) which stipulate strict protocols for the appointment of experts and preparation of technical reports.