The Practical Lawyer


Knotweed – nuisance

Last year, we had county court claims in Cardiff and Truro in which it was held that the encroachment of Japanese knotweed would be actionable as a ‘private nuisance’. The Cardiff cases have now gone to the CA, which has confirmed that there is a ‘nuisance’ – but for entirely different reasons.

The legal logic in the county court had been straightforward: the homeowners suffered a ‘loss of enjoyment’ of their property, through its diminution in value (because lenders will not grant mortgages if knotweed is present). Thus, they were entitled to damages – the diminution in value of the properties. The CA disagreed and found its own reason for there to be liability:

  • Presence of knotweed on neighbouring land may reduce the value of the claimant’s land – but that is not an actionable nuisance. The purpose of nuisance is ‘not to protect the value of property as an investment or a financial asset’, but to protect the ‘right to exclusive possession’ and ‘the use in enjoyment of the land’. In short, diminution in value could not, of itself, be an interference with the use and enjoyment of land. This leads to an important conclusion: A does not have a course of action if B does something (or omits to do something) on B’s land that leads merely to a reduction in value of A’s land. It will only be actionable if B interferes with the ’comfortable and convenient enjoyment’ of A’s land.
  • But, if there is an encroachment the position is different. Whereas the county court thought there had to be physical damage to the claimant’s land (eg damage to foundations), the CA disagreed. In its view, the encroachment of knotweed on to one’s land is ‘a classic example of interference with the amenity of the land’. It is ‘a “natural hazard” that affects the owner’s ability fully to use and enjoy the land’. In this particular case, the defendant (Network Rail) knew there was knotweed on its own land; knew there was a risk of spreading to the claimant’s land; and it failed reasonably to deal with that risk. Accordingly, it was liable.

So, Network Rail was liable for the knotweed – but what was the claimant’s remedy? The county court had awarded damages based on the diminution in value of the property but that was impliedly disapproved of by the CA. However, the CA did not interfere with the award of damages – but gave no guidance as to the proper level of damages!

There are strong arguments that the damages should be for the costs of remediation (ie removing the knotweed) only. Insurers will no doubt argue that there is no evidence to support claims that market values are reduced if insurance-backed treatments are carried out. In the absence of data showing reductions in value and if remedial works had been carried out, it is difficult to see how additional damages may be payable. At the same time, the CA seemed to concede the possibility of a mandatory injunction being granted before knotweed spreads from the defendant’s land to the claimant’s land – so that might well be the best remedy.

Frankly, the CA decision is unhelpful. There is now considerable confusion as to the basis of damages. To complicate matters further, there may also be difficult arguments over limitation periods: if the ’damage’ occurs when the knotweed first encroaches on the claimant’s land, then it will no doubt be argued that many claims are statute-barred!

See Network Rail v Williams [2018] EWCA Civ 1514 (this case report is available in full at Source: Hardwicke Chambers.


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