Liability For Reduction In Value Of Neighbouring Properties Due To Japanese Knotweed

Japanese Knotweed is a fast-growing invasive species and is a significant problem because it can cause physical damage to buildings and land.  It is expensive and time consuming to permanently remove.  Clarkslegal was instructed on the sale of a development site which was delayed for over a year when the buyer found Japanese Knotweed on site and insisted that the seller remove it before completion. Knotweed affects the value of property as well as its marketability and insurability and lenders will be less willing to accept a property affected by knotweed as security.

The owner of land could be prosecuted or given a community protection notice for causing a nuisance if he allows Japanese Knotweed to spread so that it grows on another landowner’s property.

The Cardiff County Court gave its decision in the joined case of Williams v Network Rail Infrastructure Limited and Waistell v Network Rail V Network Rail Infrastructure Limited earlier this year.  The Claimants were the owners of two semi-detached bungalows in Maesteg, South Wales, both abutting a railway embankment and access path owned by the Defendant, Network Rail Infrastructure Limited.  The railway embankment and path had been infested with knotweed for at least 50 years and it had spread up to the Claimants’ property boundaries and under their homes.  Concerns regarding the knotweed were raised by the Claimants in 2013.  Network Rail applied herbicide to the embankment but the treatment was intermittent and not sufficient to eradicate the knotweed or prevent its spread.

The Claimants brought their claim in private nuisance, arguing that the knotweed was preventing them selling their properties at their proper market value.   They argued that 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.

Both claims were successful.  As the Claimants could not prove that they had suffered any physical property damage, they had to rely instead on an alternative grounds to argue that an actionable nuisance existed, in particular loss of enjoyment and harm to amenity.  Traditionally these are grounds used as a basis for nuisance claims relating to unreasonable odour, dust and noise rather than to the spread of plants, but were allowed in this case.

The judge held that:-

• The ability to sell at market value is an important part of the homeowner’s enjoyment of their property and substantial interference with that 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 need for any physical encroachment of the knotweed onto the Claimant’s land for this effect on amenity to amount to an actionable nuisance.
• Network Rail had failed to do all that was reasonable in the circumstances to prevent the knotweed from causing a nuisance.

The Claimants were granted damages for

• The cost of knotweed surveys, treatment programmes and insurance-backed guarantees
• The residual diminution in value of their properties after the treatment had occurred
• General damages for loss of amenity and interference with quite enjoyment.

Network Rail was ordered to pay:

• £4,320.00 to each Claimant to cover a treatment package for the knotweed together with an insurance backed guarantee
• £10,000 and £10,500 to Mr Waistell and Mr Williams respectively for the residual diminution in value of their homes
• A general damage award of £1,400 to Mr Williams to compensate him for loss of amenity suffered in the four years since 2012 when Network Rail ought to have been aware of the actual presence of the knotweed and the risk of damage and loss.

This case has implications for large landowners, such as Network Rail, trying to control invasive species particularly along railway lines roads and rivers.  Landowners could be exposed to diminution in value claims in connection with any knotweed on their land, even where the plant has not encroached outside their property.

Network Rail has now appealed against this decision and we await the outcome of the appeal.