Dangers of Japanese Knotweed

England, Wales

Key point

A recent Court of Appeal decision means that property owners can be liable in private nuisance where Japanese knotweed from their land spreads to another person’s land and interferes with its amenity value, even though there may be no physical damage. Liability can take the form of damages or an injunction. The judgment has significant implications for landowners and agents and the review of procedures for dealing with Japanese Knotweed and any insurance arrangements is recommended.

The problem?

Japanese knotweed is a pernicious weed, not only carrying the risk of physical damage to buildings, but also making the development of land more difficult and, therefore, costly. It affects a landowner’s ability to fully use and enjoy their land.

The facts

In the case, Network Rail owned land immediately behind two properties owned respectively by Messrs Williams and Waistell, the claimants. There was a large stand of Japanese Knotweed on Network Rail’s land, which had been there for at least 50 years.

Claim and lower court’s decision

Claims were brought in the tort of private nuisance for damage to the claimants’ properties caused by knotweed rhizomes from Network Rail’s land encroaching on the properties and resulting in a diminution in their value.

The County Court found in the property owners’ favour and awarded damages. A key basis for the decision was that the pure economic loss suffered as a result of the diminution in the property value constituted an actionable private nuisance since it interfered with the quiet enjoyment of the properties. Network Rail appealed.

Decision of Appeal Court

As well as considering Network Rail’s appeal, the Court of Appeal considered two new points raised by the claimants. Could encroachment of the knotweed give rise to an actionable claim in private nuisance even if there was no physical damage to the properties? And could the presence of knotweed on the properties of itself constitute damage?

The Court of Appeal dismissed Network Rail’s appeal and reaffirmed the earlier decision in favour of the property owners, but for different reasons to those at first instance .


The lower court’s conclusion that the presence of knotweed was an actionable nuisance because it diminished the properties’ market value, was wrong in principle. The purpose of the tort of nuisance was not to protect the value of property as an investment or financial asset, but instead to protect the landowner in their use and enjoyment of the land.

Private nuisance involves either an interference with a landowner’s legal rights, or with the amenity of the land, which means the owner’s right to use and enjoy the land. However, damage is not always an essential requirement for a nuisance claim and physical damage to the land is not necessary for nuisance claims based on interfering with its amenity. Damages may still be awarded based on the objective, sufficiently serious, impact of the knotweed and rhizomes on the adjacent land’s amenity value.

Japanese knotweed, as a “natural hazard”, affects the owners’ ability to fully use and enjoy their land and, therefore, its amenity value. On the facts as established by the lower court in this case Network Rail knew about the presence of knotweed on its land, ought to have been aware of the risk of damage and loss of amenity to adjoining properties and failed reasonably to prevent the interference with the claimants’ enjoyment of their properties. This diminished the claimants’ ability to use and enjoy the amenity of their properties. On that basis, the award of damages to the claimants for this nuisance was upheld.


This decision highlights the importance of landowners being aware of Japanese knotweed on their land, not only for the impact on their own land but also because of the possibility of it encroaching onto other land. This gives rise to the risk of private nuisance claims based on interference with amenity (even though there may be no physical damage to the land in question) and potentially being subject to damages or injunction awards. Doing nothing is not an excuse - a nuisance can be caused by inaction or omission as well as by positive activity. The judgment is likely to be of interest to many and permission may be sought for leave to appeal further. In the meantime landowners and those responsible for managing land should consider what procedures are in place to identify and treat Japanese Knotweed and take appropriate measures to mitigate against the risk of civil claims for nuisance.

Network Rail Infrastructure Ltd v Williams and Waistell [3 July 2018].