In March 2017 a County Court decision held that Network Rail was liable after Japanese knotweed grew close to neighbouring terraced houses. The owners of the properties had been “trapped” by knowledge of knotweed, and could not sell because banks and mortgagees would not grant mortgages on affected properties. It was held that Network Rail was liable in private nuisance and had to pay damages.
Although this is a County Court decision, it does raise very interesting issues. In this particular case, the Judge held that Japanese knotweed became actionable as soon as it grew within 7 metres of a neighbouring building. Thus, Network Rail was liable for the knotweed even before it spread onto the neighbouring property (which is why one commentator described this as a new form of “proximate” nuisance. Importantly, there is no evidence of physical damage to any of the buildings – but the reality was that the presence of knotweed made the properties unmortgageable and therefore of lower value. Moreover, the expert evidence was that even if the knotweed was treated there would be residual diminution in the value of the properties (because of the approach of lenders). The key point is that no physical damage had occurred and the use of the land was not interfered with – but in the Judge’s view the value of the property lies not simply in its use or enjoyment, but can include the ability to sell it at a proper value. In the Judge’s opinion this was not the same as “pure economic loss” and was thus recoverable as damages.
Clearly, some would argue with this decision. But, the warning signs are clear – property owners who do not take appropriate steps to stop knotweed from growing within 7 metres of neighbouring buildings are potentially liable in nuisance. In practical terms, this is an enormous potential liability.
There is one basis upon which the case can be criticised. The knotweed had not intruded onto the neighbour’s land or caused damage. Hence the description of it as “proximate” – but landowners can do many things on the land which might detract from the value of neighbouring properties, but are they all actionable?