In 2018, the Court of Appeal upheld the County Court decision in Network Rail Infrastructure Ltd v Williams and another, that Network Rail had caused an actionable private nuisance by failing to take reasonable steps to prevent Japanese knotweed from affecting domestic properties next to its railway embankment. This was not because it diminished the market value of the neighbouring properties (this would have extended the tort to a claim for pure economic loss). However, the risk of future physical damage from the knotweed, increased difficulties for landowners in developing the land, Network Rail’s knowledge of the presence of the knotweed and its failure to prevent interference with the claimants’ enjoyment of their properties were sufficient to give rise to a cause of action in nuisance.
Japanese knotweed is an invasive plant which can cause serious damage to buildings and land, through its root systems (rhizomes), potentially affecting the marketability and insurability of properties and consequently their value.
An owner or occupier who allows knotweed to spread onto neighbouring land may be liable in common law private nuisance to pay damages to the owner of neighbouring land for loss of enjoyment, property damage and costs of removal. The principles of common law nuisance apply such that the nuisance must be substantial or unreasonable and can arise from either a single incident or a “state of affairs”.
Claims can be brought in nuisance or negligence and the leading case on damage to property caused by tree roots is Delaware Mansions v Westminster City Council  in which the House of Lords provided the test to be used:
- When is there a duty between neighbours?
- Did the roots cause the damage to the neighbouring property?
- Was that damage reasonably foreseeable?
- Were there any practicable steps that could have been taken to minimise or avoid the damage?
- Was there a reasonable response to the damage?
In this case, the rear wall of the claimants' bungalows was adjacent to a path owned by Network Rail, which led down to an embankment, also owned by Network Rail, on which a large amount of Japanese knotweed had been present for at least 50 years.
The claimants brought claims for private nuisance on the ground of encroachment, claiming that the knotweed had spread into the foundations of their properties and was preventing them selling at market value. These claims were refused because there had been no physical damage to their properties. However, the Recorder held that, on the balance of probabilities, Network Rail had failed to carry out its obligation as a reasonable landowner to prevent interference with the quiet enjoyment of the claimants' properties, causing a continuing nuisance and damage and the claimants were awarded damages for diminution in the market value of their properties.
Network Rail appealed against the County Court decision, on the following grounds:
- The Recorder had been wrong to say that, where a homeowner suffers diminution in the value of their property because of the presence of knotweed, the pure economic loss suffered constitutes an actionable private nuisance on the basis that it interferes with the quiet enjoyment of their property.
- The Recorder had been wrong to find that there was a causal link between National Rail’s breach of duty and the diminution in value of the claimants' properties.
The claimants added further reasons for upholding the County Court judgment:
- Encroachment without physical damage can give rise to an actionable claim in private nuisance.
- The presence of Japanese knotweed roots and rhizomes on the claimants’ properties constituted damage in any event.
The Master of the Rolls, Sharp LJ & Leggatt LJ dismissed Network Rail's appeal but for differing reasons.
General principles of common law private nuisance
The Court firstly set out a useful summary of the general principles of nuisance:
- A private nuisance is a violation of property rights involving either an interference with the legal rights of an owner of land, including a legal interest in land, or interference with the amenity of the land.
- The three general kinds of nuisance (encroachment, physical injury and interference), are just examples of violations of property rights. Any rigid categorisation could undermine a proper analysis of factual situations which did not fall squarely within one category.
- Damage is not always an essential requirement of the cause of action - the concept of damage in this context is a highly elastic one. It is well-established that, in the case of nuisance through interference with the amenity of land, physical damage is not necessary to complete the cause of action.
- Nuisance may be caused by inaction or omission as well as by positive activity. An occupier will be liable for a continuing nuisance created by another person if, with knowledge or presumed knowledge of its existence, they fail to use reasonable means to bring it to an end when they had ample time to do so. An occupier will also be liable if they fail to act reasonably to remove a hazard on their land which they are aware of and where it is foreseeable that it will risk damaging their neighbour's land.
- The broad unifying principle in this area of law is reasonableness between neighbours.
No actionable nuisance for diminution in value
Network Rail's first ground of appeal succeeded. The Recorder had been wrong to find that the presence of knotweed was an actionable nuisance because it diminished the market value of the claimants' properties. The purpose of the tort of nuisance was not to protect the value of property as an investment - it was to protect the landowner in their use and enjoyment of the land. The Recorder's decision extended the tort of nuisance to a claim for pure economic loss and this would be a 'radical reformulation of the purpose and scope of the tort'.
Encroachment without physical damage
However, the court upheld the original County Court judgment on the basis of the claimant's additional reasons.
Network Rail's knowledge of the presence of knotweed and its failure reasonably to prevent interference with the claimants' enjoyment of their properties were sufficient to give rise to a cause of action in nuisance. There was no reason why a claimant should not be able to obtain a final injunction where the amenity value of land was diminished by the presence of rhizomes even though there was no physical damage at the time.
(Network Rail's second ground of appeal failed - their argument that the issue of damages should be remitted to establish whether its expert would adjust his view of market value having regard to the full extent of the Japanese knotweed in the area for many years, was refused.)
- The case highlights the need for landowners to take the problem of Japanese knotweed seriously. In terms of the financial impact for large landowners and local authorities, it is not only the potential legal action that may prove costly but also the impact that the presence of Japanese knotweed may have on a local authority's own properties.
- It is difficult, although not impossible, to eradicate Japanese knotweed but to do so, a landowner needs to have knowledge of where the weed is established. This requires an assessment of the whole of the estate to include neighbouring properties to prevent re-infestation. A concerted effort with the use of trained operatives over a sustained period of cutting, treating and removing the vegetation is required.
- In legal terms, this case is helpful in drawing a line under any argument that diminution of value, simply by virtue of encroachment of this weed is actionable and recoverable. The Master of the Rolls made it perfectly clear it is not, stating that such an approach would be a "radical reformulation of the purpose and scope of the tort [of nuisance]". Accordingly, claims for diminution of value of a property without actual damage are likely to fail.
- What is less helpful to landowners is that the Court found that the mere presence of Japanese knotweed may be an actionable nuisance on the basis that it is unlawful interference with the quite enjoyment of the owner's land. Much weight was placed on the fact that rhizomes and roots from Japanese knotweed are considered hazardous, with numerous regulations controlling the way they should be handled. It may be a concern for local authorities that the mere presence of roots may be extended to other innocuous species such as street trees if it can be demonstrated that their presence interferes with the owner's reasonable enjoyment of their land. We are of the view that this would be difficult for a claimant to prove but it may be easier in respect of other nuisances, such as noise, dust and so forth.
- It is also interesting to note that the damages awarded at first instance were upheld but for compensation in respect of loss of amenity value. The award for what is ostensibly an award for distress and inconvenience was in excess of what would normally be awarded in a tree root subsidence case. The authority of Eiles v London Borough of Southwark  CA set down a benchmark which tends to be followed with such damages being awarded at £200 per annum. No commentary was given on the rationale behind upholding the damages so it remains unclear whether the £200 per annum benchmark has been disturbed or not. We are of the view, probably not.
For further information please contact Gabriel Fay who is both a qualified arborist and lawyer and head of our Arboricultural Law department. Through our loss adjusting team, preferred arborist experts and specialist legal team we can proactively, collaboratively and commercially help you from inception of the claim through to conclusion of litigation, reducing costs whilst at the same time assist you to manage your risks. Read more about our service offering here.