Japanese knotweed and the courts

Civil claims form most knotweed cases. These claims usually relate to financial loss, property damage or interference with the enjoyment of land.

Encroachment and private nuisance

Encroachment cases are the most common. A private nuisance claim may be brought when knotweed spreads from one property to another, affecting the neighbour’s ability to use or enjoy their land or impacting the property’s value.

Courts assess:

• whether knotweed originated on the defendant’s land
• whether the defendant knew or ought to have known about the infestation
• whether reasonable action was taken to control or prevent spread
• the extent of loss or inconvenience suffered

If successful, the claimant may recover:

• the cost of treatment
• diminution in property value
• professional expenses such as survey or expert witness fees
• compensation for loss of enjoyment or inconvenience

Misrepresentation during property sales

Where a seller states on the TA6 Form that the property is not affected by knotweed, but evidence later emerges showing it was present, a buyer may bring a claim for misrepresentation.

Courts look for:

• whether the seller knew or should have reasonably known about the knotweed
• whether the TA6 Form was answered truthfully and with reasonable care
• whether the buyer relied on the information when purchasing

Claims may involve treatment costs, loss in value and associated expenses.

Negligence and professional liability

Surveyors, estate agents and other property professionals may face claims if they fail to identify visible knotweed or fail to follow professional standards, such as those set out by RICS.

A negligence claim may arise where:

• knotweed was present and identifiable at the time of inspection
• the professional did not exercise reasonable skill and care
• the buyer suffered financial loss as a result

These cases often rely heavily on expert evidence, historical photographs and site assessments.

Nuisance claims against public bodies and large landowners

Public bodies and organisations with extensive land holdings, such as Network Rail, local authorities or housing associations, may face claims if unmanaged knotweed is affecting nearby residential land.

The Waistell vs Network Rail decision confirmed that both encroachment and the mere presence of knotweed on adjoining land can be grounds for damages if the plant restricts the neighbour’s ability to fully use or sell their property.