Knotweed nuisance: Court of Appeal confirms liability for landowners

6th July 2018

The Court of Appeal has confirmed that landowners who fail to control Japanese Knotweed, allowing it to encroach on to neighbouring properties, can be held liable for nuisance. Martin McKeague and Jeremy Moore, partners in Walker Morris’ Real Estate Litigation and Real Estate transactional teams respectively, explain and offer their practical advice.

Nuisance and the Network Rail case

Japanese Knotweed is notorious for causing physical damage to buildings through its rapidly spreading roots. It is particularly difficult, and often expensive, to eradicate. This can have an adverse impact on the value of a property, affecting marketability and also the attractiveness of the property as a security option for lenders and insurers.

For a nuisance to be actionable at common law, it must be proven that an unlawful interference with the use and enjoyment of the claimant’s property has occurred.

In Network Rail Infrastructure Ltd v Williams and Waistell [1], Network Rail challenged an earlier ruling that a landowner’s failure to control Japanese Knotweed can lead to a successful common law nuisance claim for damages from the owners of neighbouring properties even if no physical damage has been caused.

The neighbouring landowners owned properties which abutted the railway embankment. The embankment was infected with Japanese Knotweed, which had spread under the neighbours’ homes. The knotweed was thought to have been present on the embankment for 50 years. In 2013, Network Rail attempted to eradicate the plant by applying herbicide, but this was unsuccessful. The neighbours submitted that Network Rail was liable under common law nuisance to compensate them for the residual diminution in value of their property and the cost of removal of the knotweed. In a hearing in February 2017, Cardiff County Court agreed, ruling that the presence of knotweed was an actionable nuisance simply because it diminished the value of the neighbouring properties.

Court of Appeal clarification

In the appeal judgment published on 3 July 2018, the Court of Appeal confirmed that the presence of knotweed was an actionable nuisance for which Network Rail was liable, but for different reasons. The Court of Appeal clarified that:

• The tort of nuisance does not exist to protect the value of a property as an investment or financial asset, and so a claim cannot be established simply because the value of property is diminished by virtue of the presence of knotweed.
• Rather, the purpose of nuisance is to protect the owner or occupier of land in its use or enjoyment of that land as a facet of its right of ownership or exclusive occupation.
• The presence of knotweed imposes an immediate burden on landowners – they face an increased difficulty in their ability to develop, and in the cost of developing, their land, should they wish to do so, because of the difficulties and expense of eradicating Japanese knotweed from affected land.
• As such, Japanese Knotweed can affect landowners’ ability to fully use and enjoy their property. It therefore can (and almost invariably will) constitute a legal nuisance.

WM comment and advice

The Court of Appeal’s judgment represents a subtle but important clarification of the law:

• It is not sufficient for a claimant merely to demonstrate that the presence of knotweed diminishes the value of its property – interference with the claimant’s use and enjoyment of its land is required; however
• The facts of the difficulty and expense of eradicating knotweed (plus, potentially, the fact of lender caution) mean it is likely that, in the vast majority of cases, interference will be established as a matter of course.

The case is particularly significant for landowners with large portfolios. To minimise the risk of liability, it would be prudent for landowners to routinely carry out surveys for, and to undertake the eradication of, Japanese Knotweed as part of their general estate management. This will be particularly important as publicity surrounding the Network Rail case means that we are likely to see similar claims being made much more frequently going forwards.

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[1] Network Rail Infrastructure Ltd v Williams and Waistell [2018] EWCA Civ 1514