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The Importance of Disclosure in Property Transactions: It’s Knot Enough


The recent case of Downing v Henderson (2023) has re-highlighted the crucial importance in disclosing the presence of Japanese Knotweed in residential and commercial property transactions.

The case, heard earlier this year, saw Mr Henderson ordered to pay £32,000 in damages and £95,000 of Mr Downing’s legal costs, following a misrepresentation made during the sale of his house in 2018. The root of the misrepresentation: Japanese Knotweed.

In the process of the sale of his £700,000 house to Mr Downing, Mr Henderson answered ‘no’ to the question in the Property Information Form (TA6) which clearly asked if the property had been affected by Japanese Knotweed. However, when Mr Downing moved into the property, he found Japanese Knotweed stems at the rear of the garden.

In the course of the trial, experts appointed by Mr Downing found evidence that the Japanese Knotweed had been cut back and had been treated previously. Mr Henderson’s defence, that he was not aware of and had not been made aware of the existence of the weed, was dismissed by the Judge.

What is Japanese Knotweed?

Fallopia japonica, more commonly known as Japanese Knotweed, is a non-native plant to the UK, remarkably well known for its destructive potential in the context of the property market.

The bamboo-like plant is naturally dense and can grow up to 10cm per day – however, it is Japanese Knotweed’s extensive root systems (sometimes reaching 3m deep and 7m wide) that can cause serious structural damage to buildings if left untreated.

The consequences of failing to identify the presence of Japanese Knotweed can be profound when purchasing residential property, existing commercial property, or land earmarked for development.

  • Property Devaluations – Not only can the value of a building or plot of land be diminished where Japanese Knotweed is present, but the insurability and marketability of the land can be impacted. In some cases, lenders may not be willing to fund commercial developments where remediation costs could spiral.
  • Penalties and Prosecution – Failure to comply with strict guidance on Japanese Knotweed can have serious consequences – including imprisonment under the Wildlife and Countryside Act 1981, where contaminated soil has been moved incorrectly. There is also a positive duty on landowners to prevent it from escaping onto adjoining land and causing a nuisance.
  • Remediation Costs – Japanese Knotweed can take years to eradicate, as even with regular treatment, the treatment may only temporarily supress growth, leaving traces of weed in the soil. The cost of treatment can fluctuate wildly – with an extreme example being the treatment of Japanese Knotweed at the Queen Elizabeth Olympic Park. Less than 2% of the site was impacted by the weed and yet necessary treatment and removal works cost approximately £70 million and took several years to remove.

What can I do as a Buyer or Seller?

Japanese Knotweed is not a new issue for buyers or sellers of residential and commercial property; however the Downing v Henderson case has re-highlighted the serious financial and reputational risks of providing insufficient information about the presence of the weed in property transactions.

As a seller, it is critically important to declare if the property or land is or has been affected by Japanese Knotweed prior to exchange and completion. Considering the Downing v Henderson case, if as a seller you are unsure of the existence of the weed, it is important to disclose this as soon as possible. In residential conveyances, you should tick ‘not known’ in the TA6. If you are aware of the presence of Japanese Knotweed, you should provide as much information as possible to the seller.

As a buyer, you should scrutinise the information provided by the seller, and if insufficient information has been provided, raise specific enquiries in relation to Japanese Knotweed. If the seller is unsure and cannot adequately answer any queries about Japanese Knotweed, you can mitigate any future risks of uncovering the weed by appointing ecological experts to carry out an inspection prior to exchange and completion.

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