New ruling on Japanese knotweed – Defendants beware? Time will tell…

Instead, the Court of Appeal held that a residual diminution in value was a recoverable loss in circumstances where the defendant failed to inform the claimant of the existence of Japanese knotweed, in breach of its duty of care, coupled with an encroachment onto the claimant’s property or an impact on the claimant’s quiet enjoyment of the land.

The ruling potentially paves the way for an influx of damages claims.

Davies v Bridgend County Borough Council¹

In the Davies case, a homeowner claimed against the local authority, alleging that the value of his home had been diminished as a consequence of Japanese knotweed (a highly invasive species of plant, which can be difficult and expensive to remove) spreading from a nearby council-owned cycle track into his garden. It was claimed that the claimant only became aware of the issue affecting his property in 2017 whereas the council had been aware since 2013, but only took action in 2018. The council accepted that it had breached its duty to the claimant during that time.

In the court of first instance, the district judge, citing the decision in the earlier case of Williams and Waistell v Network Rail Infrastructure Ltd² found that whilst there was an actionable and continuing nuisance between 2013 and 2018, the claim for residual diminution in value had to be dismissed because it amounted to a ‘pure economic loss’, which is not recoverable in cases of Japanese knotweed nuisance. Pure economic loss, simply put, is a financial loss or damage suffered which does not arise as a consequence of any other physical damage. This decision was upheld on the first appeal.

Encroachment of Japanese knotweed

However, the Court of Appeal determined that the earlier judges’ interpretation of the Williams case was incorrect, and overturned the decision on residual value. In doing so, the Court of Appeal distinguished the earlier Williams case from the present one. In considering Williams, the Court of Appeal determined that there can be no nuisance if there is no encroachment of the Japanese knotweed (specifically rhizomes). This was because the measure of damages in those circumstances would be the reduction in the value of a property caused by having Japanese knotweed next door, which is an irrecoverable loss. However, the distinguishing feature in the Davies case was the encroachment. The Court of Appeal went on to determine that where there has been an encroachment, there has been physical interference with that property and as a result, consequential losses such as diminution in value become recoverable.

Whilst the above might cause some alarm bells to ring, it is worth noting that the Davies case relates only to a residual diminution in value where treatment has already occurred and there has been encroachment. Also, it was conceded, in this case, that the cost of treating the Japanese knotweed was not recoverable as that was a cost that would have been incurred regardless of the breach of duty – because there had been a spread (in 2004) before the date of breach (2013 when the local authority should have been aware of the breach). However, in circumstances where the breach gives rise to increased costs (by which we mean the treatment has cost more as a result of the breach), it is likely that a claimant would be entitled to the increased amount.

The decision continues to uphold the long-established principle that there is no actionable nuisance caused by the presence of Japanese knotweed simply because the presence of it diminishes the value of neighbouring property.

What can we take from the recent decision?

Whilst the above case was determined on its own facts, it sets a stark warning to landowners that they could be liable for losses previously thought to be irrecoverable, specifically residual diminution in value, in circumstances where a neighbouring landowner can demonstrate encroachment.

In light of the above, it is all the more important that landowners take immediate action to act on and remove Japanese knotweed so as to avoid falling afoul of their duty of care to neighbouring landowners.

If you have any questions regarding the topics raised in this ebriefing, please contact Liam Fitzgerald in the property litigation team.

¹Davies v Bridgend County Borough Council [2023] EWCA Civ 80

²Williams and Waistell v Network Rail Infrastructure Ltd v [2019] QB 601

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