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TREE ROOT SUBSIDENCE 

Summary of this section

The mechanism of subsidence claims caused by tree roots – damage consists in impairment of the load-bearing quality of the subsoil – the correct defendant – the ‘Leakey’ measured duty of care (nuisance category 3) – foreseeability is a necessary ingredient – the question of notice – causation – contributory negligence – remedies – compensation for the ‘necessary and remedial work’ – ‘encroachment’ a misnomer when describing these cases.

Introduction

Tree root subsidence cases concern structural damage to buildings caused by desiccation of the sub-soil by the unchecked growth of roots from a neighbour’s tree or hedge.

It has frequently been pointed out that disputes about damage caused by the actions of tree roots “call for the application of the general law of negligence and nuisance”.  They are cases which fall within the category of cases where damage has been caused by some natural thing over which a defendant should exercise control, i.e. by reference to a ‘measured duty of care’ (Sedleigh-Denfield, 1940 and Leakey, 1979).

Whilst there is “no specific set of principles applicable to cases of this type alone” (Berent, 2012), there is a sufficient body of authority dealing with tree root subsidence cases to make reference to them here on their own as a separate topic.

A general summary of the key areas of law is to be found now in The Central Gurdwara (2009).  The key issues can be identified by addressing the following, considered in more detail separately in this section of the website:

  • What is the nature of the damage which must be proved to succeed in a claim for tree root subsidence?
  • Who is the correct defendant?
  • Does the claimant have to demonstrate negligence?
  • Foreseeability and the boundaries of negligence in the context of tree root subsidence
  • What elements are taken into consideration in assessing whether damage was foreseeable?
  • Foreseeability and notice
  • The role of previous damage to neighbouring properties in establishing foreseeability
  • Causation
  • Contributory negligence
  • What remedies are available where tree root subsidence has been proved?
  • What damages are recoverable?

The nature of the damage

In order to succeed in a claim for subsidence caused by the actions of tree roots, the starting point is to question what damage the claimant has sustained.

Typically, this is on-going crack damage to a property.  Cracking, internal or external, is the consequence of the cyclical movement of the soil underneath a property.  The soil becomes desiccated by the action of the tree roots during the growing season, but recovers during the remainder of the year.  The ground will subside, but it is unlikely to recover in full.  The result will be damage to the superstructure.

The issue was considered by the Courts in Delaware Mansions (1999 and 2001, the Court of Appeal and then the House of Lords reaching the same result).  Ultimately, tree roots are considered not only to cause desiccation of the soil, but also to inhibit rehydration: this has been said to constitute “impairment of the load-bearing qualities of residential land”.

Cracking in a building is consequential on the damage to the soil which supports it.

Who is the correct defendant?

As in all cases of nuisance, the primary defendant will be the person (natural or otherwise) who is in control of the source or cause of the nuisance.  This is because that defendant is in a position to abate the nuisance.  Thus in Russell (1984) the defendant council was liable since it alone had the power to maintain the trees by reason of s.82, Highways Act 1959, even though at common law the claimant was the tree’s presumed owner.  In LE Jones (Insurance Brokers) (2002), the defendant council which had agreed to act as agent for the highway authority in the maintenance of its highway trees was the correct defendant (rather than the highway authority itself).

Does the claimant have to demonstrate negligence?

A claim for the consequences of the behaviour of tree roots is a claim where liability attaches because of the failure to keep a natural entity under control.  It is a claim where it is necessary to demonstrate that there has been a breach of a duty of care.  The claim is in nuisance, but it is one to which a degree of negligence attaches.

The historical development of this type of claim can be traced to Davey (1957) (Lord Goddard making reference to Sedleigh-Denfield (1940) and Rylands v. Fletcher (1868), itself a precursor to Leakey (1979), where a ‘measured duty of care’ requiring the control of a natural thing was first generally recognised.

The Courts still apply a conservative approach by reason of the fact that (i) these are claims in respect of natural entities (rather than by human agency) and because (ii) liability arises by reason of omissions (rather than by acts).  In such cases the interaction between the scope of the duty, and foreseeability, is important.

It is not helpful to think of these claims as nuisances by encroachment.

Foreseeability and the boundaries of negligence in the context of tree root subsidence

The role of foreseeability was given a critical analysis in The Wagon Mound (No.2) (1966), as discussed in the tree root subsidence case of Berent (2012).

Two considerations are of particular importance.  First, the correct test is expressed by the inquiry as to what is the “real risk”.  Secondly, it is not possible to separate the inquiry as to reasonable foreseeability of damage from the related inquiry as to what it is reasonable to do in the light of the reasonably foreseeable risk.  In particular, in relation to tree cases, social utility is a consideration.  A balance has to be struck, so that even where a possible injury is a foreseeable risk, it may still, in the circumstances, be reasonable to do nothing about it.

The Court of Appeal in Leakey (1979) considered the ‘measured duty of care’ as it should apply to natural nuisances (such as the consequences of the actions of tree roots).  The duty is “a duty to do that which is reasonable in all the circumstances, and no more than what, if anything, is reasonable, to prevent or minimise the known risk of damage or injury to one’s neighbour”.

It is necessary to consider, in particular, the extent of the risk, i.e. what could reasonably be foreseen as the chance that damage would be caused, what could practicably have been done to prevent or minimise the damage, the cost and whether there was sufficient time for preventative action reasonably to have been taken.  Such factors as these all need to be weighed in order to determine whether a defendant is liable.

In short, when considering whether or not there has been a breach of duty, the extent of the risk and the foreseeable consequences have to be balanced against the practicable measures which could have been taken to prevent or minimise the damage. There will be some risks which a person may be justified in disregarding.

It is settled, therefore, that tree root subsidence cases are but a species of nuisance claim (see The Wagon Mound (No.2) (1966), Cambridge Water (1993), Solloway (1981) and Berent (2012)) with the result that damage must have been foreseeable on the part of the defendant.  The duty in respect of a nuisance which is not brought about by a human agency does not arise until the defendant had knowledge, or ought to have had knowledge of the existence of the defect and of the damage created.  Foreseeability, as may be imagined, plays a large part in tree root subsidence cases.

What elements are taken into consideration in assessing whether damage was foreseeable?

The question as to whether or not the risk of damage is foreseeable is a very fact-sensitive inquiry.  As it was said in Siddiqui (2003), “the question of whether damage to a structure is reasonably foreseeable falls to be determined not in a vacuum”.  The considerable number of cases decided since Delaware Mansions (2001) has thrown up a variety of considerations relevant in these types of cases.

In Solloway (1981), the local area consisted of gravel with pockets of clay, yet subsidence caused by the action of tree roots occurred only where soil was of a ‘plastic’ quality, typically clay.  It was known amongst the experts locally that there were pockets of clay in the affected area, but each was only between five and ten square yards in extent.  The Court of Appeal (overturning the trial judge) decided that the possibility of an intrusion of clay was unlikely.  What is more, it would have been necessary to undertake intrusive tests to locate the pockets of clay, and this would have been disturbing and worrying to locals if these tests had been carried out.  The risk of subsidence damage was so remote that it was right to disregard it.  Alternatively, the cost of taking effective steps to deal with the risk would have been disproportionate.

There have been a number of cases where attempts have been made to persuade trial judges that it should be the normal expectation on the part of individual residents (at least in London) that large trees carry a risk of causing subsidence.

In Kirk (2005) such an attempt failed: the fact that a large plane tree was located on London clay, nearer to the adjacent house than it was high, does not put a person on notice of the risk of tree-root subsidence.  However, the defendant was in fact put on notice after receipt of a letter from the claimant.

In Khan (2013) too, the attempt was also made to say that foreseeability can be made out by reason of a general awareness through the media that trees can cause subsidence.  The judge decided that media reports indicating a general risk cannot establish foreseeability of the risk in respect of particular trees, but he also decided that by reason of the general risk, the location, condition and size of one of the trees, a real risk had been established and not just a mere possibility.

Khan (2013) (and the cases relied on in that case) also shows that the risk of damage by reason of a falling limb or a tree pressing up against a property is not the same type of damage as damage caused by tree roots.  These unrelated types of risk do not support a finding of foreseeability (see The Wagon Mound (No.1) (1961)).

Foreseeability and notice

The factual inquiry as to whether or not a claimant provided the defendant with notice as to the actions of the defendant’s tree roots, unsurprisingly, plays an important role in tree root subsidence cases.

In Delaware Mansions (2001), Lord Cooke, counselling against the imposition of unreasonable and unacceptable burdens on local authorities, advised that a defendant “is entitled to notice and a reasonable opportunity of abatement before liability for remedial expenditure can arise”.

As it was said in LE Jones (Insurance Brokers) Ltd (2002), “what is a reasonable opportunity to abate the nuisance is a question of fact”.

Of course notice (typically a letter advising the defendant of the need to carry out abatement works), is very good evidence to show that a risk was foreseeable, but it is now recognised that the receipt of notice is not a necessary precondition for liability to be established (see Siddiqui (2003), Kirk (2005) and Khan (2013)).

As pointed out in Delaware Mansions (2001) itself, following the receipt of notice, time should be allowed for a defendant to carry out further investigations and to contemplate what alternative means of abatement should be applied.

The provision of notice has a more important function, from a claimant’s perspective, than simply showing that the defendant was on notice that a particular tree gave rise to a risk of structural damage.  If notice is given, but the defendant does not undertake reasonable works of abatement, then it is not open to the defendant to suggest that the claimant failed to mitigate its loss by carrying out an expensive course of action such as underpinning (see Delaware Mansions (2001)).

If a defendant fails to undertake abatement works once it has been notified of a tree root problem, then it can hardly complain if expensive works become necessary.  Conversely, from the point of view of a defendant, if notice has not been given, then there may be a question as to whether a claimant can recover their full costs of repair (Kirk, 2005).  Where it makes no difference to the required works, however, nothing is achieved by giving notice (Khan, 2013).

The role of previous damage to neighbouring properties in establishing foreseeability

In Siddiqui (2003), the trial judge was persuaded that the question whether a risk is foreseeable should be determined in the light of what a reasonable landowner knew or ought to know about adjacent properties.  If the foundations of one house is inadequate to resist the actions of tree roots, then the same might be true of the foundations of the house next-door.

In Robbins (2013) the trial judge had found that because a neighbouring property had made a claim for subsidence damage, the defendant Council knew that the offending row of poplar trees was capable of causing subsidence damage.  This runs the risk of a time-consuming inquiry, involving the assistance of experts, as to whether or not the area is a tree-root ‘hot spot’.  In The Central Gurdwara (2019), for instance, 14 properties were examined by the Court, whittling relevant claims down to two in 10 years.

Causation

Causation, unsurprisingly, also plays a large role in tree root subsidence cases.  There are no special rules of causation for these types of cases, and they are the same in nuisance and in negligence.

In Loftus-Brigham (2003), a careful and closely-reasoned discussion as to causation is provided by Chadwick LJ (recommending the judgment in Paterson (1995)).  As Chadwick LJ says, questions of liability cannot be separated from questions of causation.  As it is put in Banque Bruxelles (1996), the causative event need not be the only or even the main cause of the result about which the claimant complains, since it is enough if it is an effective cause.  The rule in Fairchild is correct.

It follows, therefore, that a claimant must show on the balance of probabilities that desiccation from tree roots caused or materially contributed to the damage.  See the discussion in Siddiqui (2003) (and the cases relied on).

It is for the claimant to prove that the cause of damage is the tree in question. At the same time, there is no obligation on the part of a defendant to prove that there was some other cause of the damage.  The Court is entitled to conclude that the claimant has simply failed to discharge the burden of proof.  Moreover, a judge is not compelled to choose between two competing theories. The judge can choose the alternative, namely that the claimant has failed to discharge the burden of proof.  (See Hilda’s Montessori Nursery Ltd (2006) and the cases cited).

In Berent (2012) a straightforward test was laid out: the trees need “only to be an effective and substantial cause of the damage, not the sole or predominant cause”.

That all said, the fact that the duty of care is one which concerns a failure to act (a Leakey omission) can have important consequences.

In Robbins (2013) the trial judge held that the Council had failed in its duty to carry out a programme of crown reduction.  The causation question in those circumstances then became a hypothetical exercise as to what the defendant would in fact have done.  The judge held that, as a matter of fact, Council officers would have gone on to do more than that which prevailing advice recommended (if they had done anything at all), but that they had failed to carry out any works whatsoever.  If the prevailing advice had been followed, the damage would still have occurred.  The judge reached this conclusion because he had found that when works were subsequently done (but after damage had been caused), the council’s contractors had decided to do more than what was required of them.  He inferred that if they had got round to doing any works at an earlier stage, then they would also have done more than was required, indeed they would have done enough to prevent the damage from happening.  In short, the Council was not able to rely on prevailing general industry standards in order to avoid liability.  Contrary to the submissions made on appeal, the Council was not correct to argue that the judge should have answered the causation question by asking what the Council should have done.  The right approach was to ask the hypothetical question what the Council would have done.  That is to say that the well-known causation test as applied in Bolitho (the case of an omission to act) was the correct approach.

Contributory negligence

Apportionment for negligence has to be based on liability, not simply on causation (Loftus-Brigham (2003)).

The concept of reasonableness between neighbours applies, so that in Khan (2013), the damages were apportioned under the Law Reform (Contributory Negligence) Act 1945 to reflect the fact that the claimant did not correspond with the defendant to warn of the risk that there was tree-root subsidence.  There was an apportionment of 15% for failing to warn the defendant of both the risk of damage and of the damage which occurred.

What remedies are available where tree root subsidence has been proved?

The Court of Appeal in Delaware Mansions (1999) decided that for the purposes of assessing compensation, “the actual and relevant damage is the cost of the necessary and reasonable remedial work”, a position which was approved by the House of Lords (2001).  In the House of Lords, Lord Cooke decided that “reasonable remedial expenditure may be recovered by the owner who has to incur it”.

What damages are recoverable?

The Court of Appeal in Delaware Mansions (1999) decided that for the purposes of assessing compensation, “the actual and relevant damage is the cost of the necessary and reasonable remedial work”, a position which was approved by the House of Lords (2001).  In the House of Lords, Lord Cooke decided that “reasonable remedial expenditure may be recovered by the owner who has to incur it”.

In Delaware Mansions itself, this meant that the purchasers of the freehold could recover all of the compensatory damages necessary, even though the structural (crack) damage had all occurred prior to the date of purchase.  The decision in Masters (1977) provided support for the Delaware Mansions decisions.  In none of these cases were the Courts troubled by the issue of limitation.

Encroachment

Whilst it is still said that these types of cases can be classified as ‘encroachment’ cases, that is a classification which arises as a matter only of historical accident.  The relevant principles which are applied have very little to do with encroachment (which is a strict liability form of the tort of nuisance).  These are now dealt with under the principles relevant to the measured duty of care, as explained above.

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