​ Japanese Knotweed – Potential for Damage

A recent case[1] has provided occupiers of land with confirmation that they can obtain compensation if a neighbour allows Japanese knotweed to spread from their land, even if it has not yet caused damage.

Japanese knotweed is an invasive species of plant.  It is very difficult to remove, as even a 1cm piece of root can regenerate into a new plant within days.  The plant can grow up to 10cm in one day, and can block drains, grow between concrete slabs, and undermine brick walls.  The roots can spread up to 7 metres horizontally, and 3 metres vertically.

The presence of the plant can reduce property value by 20%, and some lenders will refuse to provide a mortgage for land with the plant on it.  There is even a risk that the land will retain a reduction in value after treatment to remove the plant, just for the fact that Japanese knotweed had been growing there.

The plant itself, and contaminated soil, will be classed as controlled waste, meaning that it may only be removed from the property by appropriately licenced operators.  Treatment can cost between £2,500 and £30,000.

In the case of Network Rail Infrastructure Ltd v Williams, two homeowners living next to a railway launched claims for compensation when Network Rail allowed Japanese knotweed to spread from its land onto theirs.  No physical damage had yet been suffered to the buildings on the land.

The Court held that it was enough for there to be a risk of future damage to the property, and the cost of professional treatment and removal of the plants, as well as an insurance policy, should be paid for by Network Rail.  The Court also held that the Claimants had suffered a loss of amenity that related to the lasting reduction in value of their properties, and awarded damages on those grounds as well.

Practical tips for homeowners:

  • Remain vigilant for Japanese knotweed on your own property – if present, then take urgent action to prevent its spread and to remove it using a professional service;
  • Keep records of your efforts to contain and remove the plant;
  • If you see Japanese knotweed on neighbouring land, notify the owner and/or occupier of that land, and ask them to have the plant professionally dealt with;
  • Keep records of any such notification/request;
  • If you see Japanese knotweed on neighbouring land, consider your financial position in the event that it might escape – do you need to remortgage soon? Do you have the funds to take legal action against the neighbour?

Here at Leeds Day we are award-winning solicitors in St Ives offering a tailored range of services to businesses and individuals with offices in Huntingdon, St Ives and St Neots, we have a significant presence as solicitors in Cambridgeshire advising individual and corporate clients in the region, and beyond. Contact us today to find out how we can help.

This article is not a substitute for independent legal advice, and is provided as a guide only.  If you are unsure of your legal position, you should seek specialist advice straight away.


[1] Network Rail Infrastructure Ltd v Williams [2018] EWCA Civ 1514

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