Japanese knotweed has blighted UK properties for over a century. The invasive plant’s roots and stems spread rapidly and have the capacity to smash through concrete, damaging a building’s foundations. Eradicating the knotweed is another headache entirely. As a result, securing finance on blighted properties can prove to be very tricky.

These issues were at the heart of the recent Court of Appeal case of Network Rail Infrastructure Limited v Williams and Waistell. Williams and Waistell each owned a bungalow neighbouring part of Network Rail’s estate from which Japanese knotweed had spread.

The County Court originally held that for “encroachment” type nuisance claims to succeed, physical damage has to have been caused to property. The difficulty faced by the respondents was that they could not prove that the knotweed had damaged their properties’ foundations. Despite this, the respondents were awarded damages in excess of £30,000 in connection with a “loss of amenity” type nuisance claim. This sum was based on the loss in the value of the respondents’ properties caused by the presence of the knotweed.

On appeal, the Court of Appeal agreed with the outcome of the decision at first instance, but for different reasons.

The Court of Appeal held that private nuisance claims, at their very core, concern the protection of the owner of land and their use and enjoyment of it, rather than protection of the market value of property. As such, damages for nuisance should not be linked to the diminution in value but should instead compensate for loss of use and enjoyment of property. The presence of the knotweed would increase the costs incurred by the respondents when developing their land (whether or not such development was currently intended). It is this increase in cost that should form the basis of the damages claim.

Crucially, the Court of Appeal also clarified that the categorisation of nuisance claims into “types” (such as “loss of amenity” type) is archaic, and the constituent parts of a valid claim are the same irrespective of “type”. As such, physical damage isn’t necessary as a pre-requisite to a successful nuisance claim as long as there is some identifiable loss of amenity.

The fact that an owner’s liability can arise prior to physical damage being caused to neighbouring property, in particular, will alarm landowners. A more proactive approach to estate management will need to be adopted by landowners who already have a knotweed problem, to identify areas of risk at an early stage so that potentially costly claims can be avoided.

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