Japanese knotweed damages allowed where use of land affected

The Court of Appeal found in favour of two homeowners from South Wales, who had sued Network Rail after knotweed from a railway embankment had spread to their properties. Its decision will not, however, "open the floodgates" to claims in private nuisance where only the market value of the property has been affected, as suggested by the county court's original ruling in the case, according to property litigation expert Pierre Smith of Pinsent Masons, the law firm behind Out-Law.com.

"Whilst the Court of Appeal has upheld the ruling of the county court, it has done so for different reasons," he said.

"The judgment does not, as feared by many, go as far as 'opening the floodgates', nor has it allowed the understandably risk-averse policies of commercial lenders to shape the law of private nuisance. Contrary to the first instance finding of Recorder Grubb, for a claim to succeed in private nuisance, it will not be enough to demonstrate a diminution in the value of the land. Rather, a claimant will need to show that their ability to use and enjoy the amenity of their land has been adversely affected to a sufficiently serious degree," he said.

"It appears that the presence of Japanese knotweed, and the well-publicised issues that this poses, will allow those affected to meet this test but in other cases, where the adverse implications are purely economic, claimants are unlikely to be successful," he said.

Japanese knotweed, described by the court as a "pernicious weed", is a fast-growing plant which is difficult to eradicate, and which spreads rapidly through an extensive network of underground roots and stems, or 'rhizomes'. While the plant itself can quickly grow to a height of over two metres, the roots can extend up to seven metres horizontally and three metres vertically, affecting buildings and construction works.

Because of the potential ramifications of Japanese knotweed on property, the Council of Mortgage Lenders (CML) has published a policy stating that it might affect the valuation of a property and might be an issue for customers whose property is affected but who cannot afford the treatment costs. The policy requires valuers who inspect property for mortgage purposes to report on the presence of knotweed within seven metres of the property to lenders, so that they can take account of it as part of the valuation process.

Sir Terence Etherton, giving the judgment of the Court of Appeal, described a claim of private nuisance as one based on "a violation of real property rights". This violation need not necessarily take the form of physical damage to property; however, it could not consist of merely pure economic loss.

"The [county court] recorder's conclusion that the presence of knotweed on [Network Rail's] land within seven metres of the claimants' properties was an actionable nuisance simply because it diminished the market value of the claimants' respective properties, because of lender caution in such situations, was wrong in principle," he said.

"The purpose of the tort of nuisance is not to protect the value of property as an investment or a financial asset. Its purpose is to protect the owner of land (or a person entitled to exclusive possession) in their use and enjoyment of the land as such as a facet of the right of ownership or right to exclusive possession. The decision of the recorder in the present case extends the tort of nuisance to a claim for pure economic loss," he said.

That being said, the Court of Appeal ruled that the encroachment of the knotweed onto the homeowners' property was "a classic example of an interference with the amenity value of the land".

"Japanese knotweed and its rhizomes can fairly be described, in the sense of the decided cases, as a 'natural hazard'," the judge said. "They affect the owner's ability fully to use and enjoy the land."

Network Rail had actual knowledge of the presence of Japanese knotweed on its own land, and was, or ought to have been, aware of the risk of damage and loss of amenity the close proximity of the knotweed posed to adjoining properties, the judge said. It also failed to reasonably prevent interference by the knotweed with the homeowners' enjoyment of their properties, he said.

"That is sufficient … to give rise to a cause of action in nuisance," he said.

Network Rail was denied leave to appeal to the Supreme Court, although it will be able to apply to the court directly in the usual way.