Roots can be removed to the boundary in the same manner as overhanging branches can, assuming removal is done with reasonable care. As per Lemmon v Webb , it was held that a neighbour could cut back from his property without notice to the owner of the tree, provided that he could do so without entering the owner’s land. In the case of McCombe v Read , such a ruling was again found, where the judge remarked that a neighbour could indeed cut back any root encroachment back to his or her boundary. Furthermore, the judge even ruled that the defendant who owned the trees must ensure that the tree roots did not encroach unto his neighbour’s land so that they could be deemed to be once again causing a nuisance. Soon after, the judge in Davey v Harrow Corp.  ruled similarly, by remarking that “if trees encroach, whether by branches or roots, and cause damage, an action for nuisance will lie”, though only if the apparent nuisance was indeed reasonably recognisable (for trees existing close to boundaries, such an issue almost certainly is). More recently, this precedent is evident in Perrin & Anor v Northampton Borough Council & Ors , where it was ruled that “root encroachment into a neighbouring property was similar to bough encroachment, and that the neighbour could lop boughs or grub roots without notice“.
Beyond mere direct encroachment and subsequent nuisance abatement, the most significant factor surrounding root encroachment onto a property is subsidence, where the soil is shrinkable in nature. In 1940, the case of Butler v Standard Telephones and Cables was one of the first to deal with the subsidence issue, and it was ruled that the line of poplar trees grown on the Company’s sports field, which were subsiding the claimant’s property, were the culprits. The line of defence the Company adopted was one of not being able to foresee that the poplars would cause such damage, though even whilst the judge did remark that the poplars were very attractive specimens, it was ruled that the Company should have appreciated the destructive potential of trees. Therefore, their defence was dismissed, and the claimant won the case. This ultimately sets the shape of things that were to come, as the precedent set was one of outlining how a tree owner must be able to recognise that trees, by virtue of their mere presence, can cause problems. Failing to recognise this and deal with such problems appropriately is, therefore, negligent.
In recent decades, the case of Solloway v Hampshire CC  continued this precedent, and ruled that where harm as a result of the moisture uptake by encroaching roots was foreseeable, action must be taken to reduce the nuisance. This case, in essence, saw the claimant’s property subside as a result of the Council’s trees, though as the area was predominantly considered to reside upon gravel, the Council had no knowledge that small pockets of clay underlay the claimant’s property. Therefore, whilst the initial judge ruled the Council were liable, at appeal it was ruled they were not, given such a geological erratic was not foreseeable: “To say that a risk of damage is reasonably foreseeable means that it is foreseeable, not merely as a theoretical possibility but as something, the chance of which occurring, is such that a reasonable man would consider it necessary to take account of it.” The judge, at appeal, also ruled that nothing short of felling the trees would have satisfied the situation, and because the Council would have not known that these trees were causing such an issue, expecting for them to have been removed prior to the issue manifesting would have been unfair and disproportionate to the level of foreseeable risk.
With further regards to the issue of subsidence, Delaware Mansions Limited & Others v Lord Mayor & Citizens of The City of Westminster  ruled that: “The encroachment of the roots was causing continuing damage to the land by dehydrating the soil and inhibiting rehydration. Damage consisting of impairment of the load-bearing qualities of residential land is, in my view, itself a nuisance.” In addition to this, the case stated that the established nuisance would continue up “until at least the completion of underpinning and piling“. Perhaps more importantly, this case continued the precedent that unreasonable and unacceptable burdens on local authorities and other tree owners must not be placed. It is not acceptable for unforeseeable harm to be anticipated and acted upon, by the owner of a tree. This precedent indeed relates back to Leakey v National Trust  and Solloway v Hampshire CC , where it was stated that only where harm is foreseeable can a nuisance be abated. In more recent times, this precedent has been echoed by Berent v Family Mosaic Housing & Islington Council , where it was ruled that subsidence damage caused by two mature plane trees was not a foreseeable threat, and again with Denness v East Hampshire DC  and Robbins v Bexley LBC . In the case of the latter, the defendant took the issue to appeal, where it was still ruled that they were liable for damage associated with tree roots (from two hybrid black poplars) causing subsidence, given they had not managed the trees in any manner for the period between 1998-2006, and only after this point had they enacted a four-year management cycle for the trees in question – all whilst the risk of subsidence was foreseeable.
Despite this, where harm is foreseeable, local authorities and owners must act (as already established). This applies also to ‘managing agents’ of a tree found to be causing damage. For instance, the judge in Le Jones (Insurance Brokers) Ltd v Portsmouth City Council  ruled that, where Portsmouth City Council were managing the tree stock of Hampshire County Council, “I do not understand on what basis it can be said that Portsmouth did not owe the claimant a duty to perform its function of tree management with reasonable care. Mr Bebb boldly submits that the only duties owed by Portsmouth were to HCC, and that only HCC owed a duty of care in tort to persons who foreseeably suffered damage as a result of inadequate tree management. I do not agree. The mere fact that Portsmouth owed a contractual duty to HCC does not mean that it owed no duties in tort to anyone else.” As a result, Portsmouth were found part-liable for the damage caused by root-induced subsidence, though it should be noted that a formal agreement was in place between the two parties that outlined the defendant’s role in managing the tree population for Hampshire County Council. Where such a formal agreement is lacking, there appears to be no current guidance on how a ruling would be made.
It must however be stressed that adequate proof must be provided in instances of subsidence, as concluded in Hilda’s Montessori Nursery v Tesco Stores Ltd . Adequate proof is, according to experts and the conclusions of the case, at least one year’s worth of monitoring and the associated data. In Loftus Brigham v Ealing Council  however, it was concluded by the ruling judge that it must be established that roots must be the “most dominant” cause of subsidence-related damage, not simply one of multiple causal agents. Interestingly, this case was overturned and sent for retrial, as it was deemed the judge was incorrect in his conclusions and that burden of proof was not on identifying roots as the “most dominant” cause, but merely a cause. Such identification of whether a tree is merely a cause relates back to Murray v Hutchinson , where the judge stated that one must “not jump to the conclusion that because they have a bad name they are always responsible for this damage.” It was ultimately ruled that the tree was found to play 25% of the role in harm caused to the property, and damages were awarded in light of this. However, the judge in Mayer v Deptford and Lewisham Councils  ruled that, even though a plane tree was found to only have accelerated subsidence damage once it had already begun to manifest via other means, full damages were to be paid, by the defendant, to the claimant.
In situations where more than one tree is found within an area known to be subsiding, care must also be taken to identify only the trees that are causing the damage. This precedent was established in Malewski v Ealing LBC , where it was argued by the defendant that trees within the garden of the property were causing the damage to the foundations. Ultimately, it was concluded that the highway tree owned by the defendant was the cause, though the precedent set on accurately proving implication of a tree was critical.
As a somewhat aside, the case of Siddiqui v Hillingdon LBC  found that damage had occurred via the removal of trees prior to development, and not from existing roots on site. The claimant had alleged that the cracking was due to soil desiccation, though it was ruled that the cracking was in fact down to heave (resulting from the removal of trees prior to development). Such a case acts as a reminder that exiting trees may not necessarily be the cause of damage. However, perhaps more importantly, the judge ruled that “modern standards of construction can be expected to take account of obvious hazards in the vicinity of the structure to be built…“, which may have implications for future claims where subsidence is an issue for newer builds on sites where trees were retained. Current case precedent does also recognise that the severance of roots may cause heave, as outlined in Park v Swindon BC .
As another partial aside, the case of Kirk & Ors v London Borough of Brent  set a possible precedent for a retrospective damage claim against the owner of trees considered to have been causing subsidence. Some years earlier, a line of properties had to be underpinned as a result of suspected subsidence damage, resulting from the moisture uptake of trees owned by the London Borough of Brent, though the Council were not notified of the underpinning works until after the work was entirely completed. The original judge rejected the claim, though on appeal it was determined that, even though there was no exact proof of the subsidence being caused by the trees, the Council should pay damages amounting to £15,000. In fact, this case influenced a more recent case where a near identical situation occurred, which was that of Robbins v Bexley London Borough Council . The High Court held that even though the local authority had not been notified of any damage to the property, the damage was still reasonably foreseeable as the trees had caused damage to other local properties and, once that was known, proactive remedial action should have been taken. When taken to appeal by the defendant in 2013, the case precedent remained as per the original ruling, and the appeal was therefore dismissed.
Other issues caused by roots, such as damage to drains, is outlined in Kennedy v Bournemouth Borough Council , where it was determined that the roots were not the principal cause of the flooding caused by blocked drains, but instead the principal cause was that of the state of disrepair with the drain pipes themselves. The court decided that the claimant was responsible for making good the drain pipes, so that tree roots could not exploit the cracks for moisture.