Summary: Network Rail has been ordered to pay damages for nuisance caused to two homeowners by its failure to control Japanese Knotweed. Despite no physical damage having been suffered at the claimants’ properties, Network Rail was held responsible for the diminution in property value caused by the presence of the weed on its neighbouring railway embankment. This decision raises the possibility of similar claims being made more frequently in the future.

What is Japanese Knotweed?

Japanese Knotweed (JK) is a fast-growing invasive species, which is capable of growing through walls, drains, foundations and surface paving, causing damage as it does so. It is able to spread rapidly via its root system, which can stretch up to 7 meters from the parent plant. Once established, its eradication is expensive and can take many years. As a result of its destructive and persistent characteristics, this plant is a well-known menace whose presence is capable of making a property less attractive to prospective buyers and diminishing its likelihood of being accepted by lenders as security.

What were the facts of these cases?

The two relevant cases, Williams v Network Rail Infrastructure Ltd and Waistell v Network Rail Infrastructure Ltd were heard together in Cardiff County Court in February this year. The claimants were the owners of two bungalows in Maesteg, South Wales. The bungalows abutted a railway embankment and access path owned by Network Rail. The roots of a large stand of JK, which had been present on the railway embankment for at least 50 years, had spread up to the claimants’ property boundaries and under their homes.

Concerns regarding the JK were raised by the claimants in 2013. Network Rail applied herbicide to the embankment, but this treatment was sporadic and had not been sufficient to eradicate the knotweed or prevent its spread.

The claimants argued that under common law nuisance, Network Rail was liable to compensate them for the cost of treatment of the knotweed in the immediate proximity of their bungalows, as well as the residual diminution in value that would remain even after the knotweed had been dealt with. Mr Williams also claimed for the distress and inconvenience he had already suffered, including from concerns as to the saleability of his property.

Both claims were successful, and Network Rail was ordered to pay £4,320 to each claimant to cover a treatment package for the knotweed (together with an insurance-backed guarantee), as well as £10,000 and £10,500 to Mr Waistell and Mr Williams respectively for the residual diminution in value of their homes. Mr Williams also received a general damages award of £1,400 to compensate him for loss of amenity suffered in the four years since 2012, which is when Network Rail ought to have been aware both of the actual presence of the JK and also (owing to RICS guidance published on the topic) the risk of damage and loss of amenity to adjoining properties caused by the proximity of JK.

So, what’s new here?

The principle that the spread of plants onto neighbouring properties is capable of constituting an actionable nuisance is not a new one. Case law has previously established that where a tree encroaches onto neighbouring land and causes physical damage to property, the owner of the land from which the offending roots or branches have originated can be liable under common law rules of nuisance to compensate for losses suffered.

In the present case, however, as the claimants could not prove that they had suffered any physical property damage, the claimants instead had to rely on alternative grounds to argue that an actionable nuisance existed, in particular loss of enjoyment and harm to amenity. This was novel, because traditionally, these are the grounds used as a basis for nuisance claims relating to unreasonable odour, dust and noise rather than those relating to the spread of plants.

The judge found that:

  • The ability to sell at market value is an important part of a home-owner’s enjoyment of their property, and substantial inference with that amenity value could constitute a legal nuisance.
  • By diminishing the marketable value of the claimants’ properties, the presence of the knotweed on Network Rail’s land had amounted to a substantial interference with their amenity value.
  • There was no requirement for any physical encroachment of the JK onto the claimant’s land for this effect on amenity to amount to an actionable nuisance. The judge drew analogy here with cases in which the use of proximate land as a brothel and sex shop had been found to impact amenity and be capable of constituting a nuisance.
  • Network Rail had failed to do all that was reasonable in the circumstances to prevent the JK from causing a nuisance. Whilst they had carried out some treatment, this was held in the circumstances to be insufficient.

What are the key ramifications for landowners?

Whilst only a county court decision, this judgement should be noted in particular by landowners who, depending on their neighbours and the extent of their property boundaries, could be exposed to diminution in value claims in connection with any JK on their land, even where the plant has not set foot off their property. To ensure that this liability risk is minimised, the eradication and control of JK should be given sufficient attention as part of wider estate management activities.

Other points to note

In many established areas of nuisance where a “loss of amenity” (rather than physical damage) forms the basis of claims (such as noise or odour nuisance), claimants often struggle to overcome the evidential burden of proving that the nuisance in question has substantially interfered with the quiet enjoyment of their property. The requirement for convincing technical evidence, against the backdrop of the often low value of damages available, has historically proved a relatively fine filter for potential claims.

In potential future JK cases for diminution in value, however, the financial backdrop will be less intimidating, and so (potentially) will the evidential burden.

A broader look at the possible significance of this judgement also prompts one to question what other uses of land or what range of potentially offensive things present on land could be similarly regarded as a “proximate” nuisance. It will be interesting to see whether this decision forms the basis for more claims to be brought which cause the courts to consider this very question.