Claims of nuisance for property damage or for loss of amenity can arise due to a variety of spreading vegetation including tree roots, bamboo and Japanese Knotweed. In this article, property solicitor Deborah Swanwick, construction lawyer Louise Elmes, and regulatory expert Jeremy Woodcraft provide some guidance for surveyors, buyers and sellers of property who are dealing with Japanese Knotweed. They also highlight the new RICS framework for risk assessment, which was announced in June 2021.

What is Japanese Knotweed and what does it look like?

Introduced to Britain in the 19th century, Japanese Knotweed affects around 4% of homes across Britain. It is a group of plants of varying heights with zig-zag stems, shield-shaped leaves, bamboo-style stems, red shoots, and forms in dense clumps with clusters of white flowers.

Why is Japanese Knotweed a problem?

Knotweed is a pest, highly invasive, destructive and difficult to eradicate. It can lie dormant and re-emerge. With an extensive root system, it can cause damage to properties and spread to neighbouring land, devaluing property and making land difficult to insure, mortgage and sell.

For years, banks have refused to lend where Knotweed was found within seven metres of the building. The ‘seven metre rule’ caused unfairness because surveyors were bound by a binary test which ruled out lending whether or not the Knotweed posed an actual threat to the property. In other words, its presence within seven metres was fatal to mortgaging and therefore, in many cases, to selling.

New guidance for surveyors

Japanese Knotweed and residential property RICS Information Paper IP 27/2012 June 2021

The new guidance emerged from a government-driven intention to facilitate lending and to enable homeowners to insure or sell their homes.

Section 5 An Assessment Framework is a risk assessment of Japanese Knotweed and it takes into account the real risk to property and addresses the concerns of lenders and insurers. Section 5.5 categorises the risk into four degrees of severity so that lenders and insurers can make a qualified and detailed decision on properties with Knotweed.

The RICS has replaced the binary seven metre test with a broader and more detailed assessment using a Table of 4 categories and section 5.5.2 provides that any risk within categories 3 and 4 will be referred automatically for further investigation by a qualified and experienced person who will produce a management plan under section 5.7.

In category 2 of the risk Table, surveyors should identify Knotweed’s presence if visible within seven metres of the boundary of adjacent land but more than seven metres away from habitable spaces, conservatory or garage on the property being surveyed, as this is information a buyer should know about. Category 1 of the risk Table applies where no Knotweed exists.

The RICS hopes that lenders will begin to adopt more consistent and balanced policies and that Japanese Knotweed should become just another consideration in the valuation process, like asbestos, lead and radon, rather than a circumstance which stymies sellers. Time will tell whether the RICS’ hopes come to fruition; the fear is that, despite RICS intervention, Japanese Knotweed will remain an insurance and lending hurdle very difficult to overcome.

Category Descriptors
4Japanese Knotweed is within 7 metres of a habitable space, conservatory and/or garage, either within the boundaries of this property or in a neighbouring property or space;


Japanese Knotweed is causing serious damage to outbuildings, associated structures, drains, paths, boundary walls and fences and so on.

Further investigations by an appropriately qualified and/or experienced person are required.

3Although Japanese Knotweed is present within the boundaries of the property, it is more than 7 metres from a habitable space, conservatory, and/or garage. If there is damage to outbuildings, associated structures, paths and boundary walls and fences, it is minor.

Further investigations by an appropriately qualified and/or experienced person are required.

2Japanese Knotweed was not seen within the boundaries of this property, but it was seen on a neighbouring property or land. Here, it was within 7 metres of the boundary, but more than 7 metres away from habitable spaces, conservatory and/or garage of the subject property.
1Japanese Knotweed was not seen on this property, but it can be seen on a neighbouring property or land where it was more than 7 metres away from the boundary.

What are your legal duties if you know there is Japanese Knotweed on your own land?

If there is a risk of it spreading to neighbouring land or it has spread to neighbouring land, then the owner is under a legal obligation to prevent or stop the nuisance by removing the Knotweed with due care. It would be unlawful to fail to do so under the Wildlife and Countryside Act 1981 which classes Japanese Knotweed as a ‘controlled plant’. There are specialists who treat and manage Knotweed.

Transactions – Tips for buyers

  • Ensure that your surveyor’s engagement includes for identifying Japanese Knotweed.
  • Your solicitor should raise enquiries on Japanese Knotweed on the property and adjacent land.
  • If the property is affected by Japanese Knotweed, you must inform your lender, inform your insurer and get a quote for its removal and management from a reputable specialist. Removal and management costs could be offset in a price adjustment.
  • Consider obtaining specialist insurance if your standard insurance will not cover the risk.

Transactions – Tips for sellers

What to do if you have Japanese Knotweed on your own land

It is not a criminal or civil offence per se to have Knotweed on your land but it is unlawful to sell the land without disclosing it if enquiries are raised. And it is unlawful to allow Knotweed to spread to neighbouring land if you know it to be at risk of doing so or has done so.

If an enquiry is raised by a buyer concerning the existence of Japanese Knotweed, then a seller will have a legal duty to disclose its existence if the seller knows it to be there. Sellers of domestic property can expect to receive formal enquires in Law Society Property Information Form (TA6) containing a specific enquiry about Japanese Knotweed. Enquiry 7.8 on TA6 is limited to the land in question being sold.

However, the principle of caveat emptor applies, meaning that if a buyer does not ask, then a seller is under no obligation to disclose its existence. Knotweed is not a ‘notifiable plant’ under the Wildlife and Countryside Act 1981.

If anyone causes Knotweed to enter wild land, section 14(2) of the Wildlife and Countryside Act 1981 will apply: ‘Subject to the provisions of this Part, if any person plants or otherwise causes to grow in the wild any plant which is included in Part II of Schedule 9, he shall be guilty of an offence.” Japanese Knotweed offences under this Act are enforced by the police and local authority.

What if there is Japanese Knotweed on neighbouring land?

Similarly, there is no obligation to disclose your knowledge about Knotweed on land you do not own unless a specific enquiry is raised to that effect.

Claims against surveyors

If the scope of your surveyor’s engagement should have identified Knotweed but did not do so, there may be a claim for damages to be made against your surveyor for professional negligence. In assessing whether your surveyor acted with reasonable competence, a court or tribunal may take into account the RICS Information Paper referred to above. This may result in different findings as to liability and/or damages awarded compared to previous cases, particularly where the Japanese Knotweed falls into category 2 on the risk Table.

Claims against neighbouring owners

If you are in the unfortunate position to have Japanese Knotweed spreading from neighbouring property onto your own property, you may have a claim against those neighbours through the civil courts. This would be a claim in nuisance for remedies, including damages for loss of enjoyment and diminution in value of your property, the costs of removal or treatment of the Japanese Knotweed, the costs of rectification of damage to your property and an injunction preventing re-infestation.

Even if the Japanese Knotweed on a neighbouring property has not encroached onto your property, if its presence has in fact decreased the value of your property, you may also have a claim.

The courts may take into account the RICS Information Paper in reaching a decision: the effect may be felt most keenly on the extent of decrease in value of your property and the extent of Japanese Knotweed to be removed or treated.

Network Rail v Williams [2018] Court of Appeal

In recent years, homeowners have been successful in bringing large claims against Network Rail after Knotweed spread from railway lines into their gardens. In this landmark case, the Court of Appeal dismissed Network Rail’s appeal on grounds that the claimants’ ability to enjoy the amenity and utility of their properties had been diminished by Knotweed.

However, any similar future claims may be assessed differently after the new method of assessment under the RICS Information Paper 2021 is applied.

Local authority involvement

Should the local authority become aware of the presence of Japanese Knotweed on land, they can serve a community protection notice (under the Anti-Social Behaviour Crime and Policing Act 2014) requiring the owner to take specified steps to deal with the same. Failure to comply with the notice is a criminal offence under the Act and an owner can be fined a significant amount of money.

The Magistrates’ Court is empowered under the legislation, at the same time as convicting the owner, to make a remedial order setting out steps that must be taken (usually with a timetable attached) to address the issue. It is therefore a lot cheaper and easier to deal with the Knotweed either before the local authority become involved or as soon as the notice is served.

If you believe you have a Japanese Knotweed claim, it is important to seek advice from a legal expert. Please do get in touch with Deborah Swanwick, Louise Elmes or Jeremy Woodcraft using the below details.

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This article is for general information purposes only and does not constitute legal or professional advice. It should not be used as a substitute for legal advice relating to your particular circumstances. Please note that the law may have changed since the date of this article.