Knot so Weedy Afterall? RICS issues new draft guidance on Japanese Knotweed

19 July 2021. Published by Alexandra Anderson, Partner and Katharine Cusack, Partner

The RICS is seeking consultation on its Japanese Knotweed draft guidance note.

The consultation, which you can access here, opened on 22 June 2021 and closes on 3 August 2021. 


The presence of Japanese Knotweed (JKW) can be a real issue for owners of residential properties and those carrying out valuations or surveys on them. The stigma that attaches to the presence of this invasive weed can reduce the value of a property and can cause much stress to the owners, particularly when it crosses boundaries. Neighbouring property owners may refuse to treat JKW which can ultimately end in costly litigation, in addition to the expense of the treatment itself. Furthermore, where professionals fail to identify the presence of knotweed, it can leave them open to claims for breach of duty.  It is imperative that adequate insurance is obtained to cover all risks relating to the presence of JKW.

Previous guidance from RICS on this risk was in the form of the Information Paper issued in 2012. Since then, there have been many developments by way of research and studies on JKW. RICS is now seeking to assist the marketplace and provide updated guidance reflecting these developments. 

The guidance should be read alongside RICS Valuation Global Standards (the Red Book) and will assist in understanding the issue of JKW, its effects on properties and therefore on valuations. The key aim of this guidance is to open up the market further and try to reduce the stigma attached to JKW, particularly for lenders when making lending decisions. 


The overarching message in the draft guidance is that the actual impact of JKW is not as devastating as previously thought. Common perception of properties that have JKW, or that are adjacent to properties that have it on their land, is that their value must be reduced to reflect its presence. RICS describes this as resulting in parties becoming "unduly risk averse" and having a "disproportionate fear of the problem"

To help combat this fear, the draft guidance aims to educate and shift the focus from eradicating JKW to managing it effectively. 

We recommend all professionals carrying out surveys or valuations on residential properties read this guidance and we set out some of the key points below.

  1. RICS confirms that JKW is unlikely to cause damage to structurally sound buildings. However, it can cause damage to more light structures, such as walls, drains and other ancillary structures. 
  2. The distance in which JKW can be expected to have some influence on a structure has been reduced from 7m from 3m. RICS confirms that research has indicated that 7m was too generous a measurement and in fact, 3m for the spreads of the root/rhizome was more appropriate. 
  3. Consideration must be given to the environmental implications of any treatment recommended, which can include the use of herbicides and/or excavation. Some treatment options can take years to reach a conclusion and should be backed by an insurance guarantee in case of reappearance.
  4. The specifications/limitations of a survey or valuation, as well as the scope of duty in the retainer, must be made clear to clients. This will ensure the professional (and the client) know the extent of the inspection taking place as well as the different options available to them.  If a client wants specific advice/confirmation on the presence of JKW, the professional should recommend the instruction of a specialist remediation company, that is part of a recognised trade body. 
  5. Professionals are advised to carry out pre-inspection checks and research into the locality, which may give an indication of whether JKW could be prevalent in the area of the subject property. 
  6. Professionals must ensure they make accurate site records when carrying out inspections, including supporting evidence (either verbal, visual or documentary) where possible. 
  7. The draft guidance introduces a new assessment method to assist professionals in carrying out a structured assessment of a JKW infestation. The assessment results in a categorisation of the infestation, which sets out: (i) the level of impact; (ii) if action is necessary; (iii) whether remediation is required; and (iv) whether the instruction of a specialist is required. The assessment is primarily aimed at lending, in order to provide the lender with the necessary detail they need to make a decision on the subject property. If the assessment is used for non-lending purpose and there is any JKW present, the professional should always recommend a specialist is required for further advice. 

Did you know? 

  • There are smart phone apps that can assist you in identifying whether a plant is JKW.
  • There are specialised knotweed detection dogs that can help sniff out rhizomes hidden underground.
  • Plant specialists are developing ways to tackle JKW that are actually beneficial to the environment.


RICS confirms this guidance is designed to provide "clarity and confidence in the market when Japanese Knotweed is encountered". Its aim is to move away from the belief that eradication is the only option and that residential properties may be 'unsafe' or susceptible to damage where it is present.  The guidance seeks to promote effective management of JKW and give professionals the confidence to carry out inspections and make assessments that involve JKW. 


  • Is it a valuation or survey?
  • Is the client clear on the limitations/Terms & Conditions/Terms of engagement?
  • Have you obtained information from owner/seller of the subject property (any issues with JKW/any guarantees/warranties or management plan)?
  • Have you carried out pre-inspection research and understand general area (at least information on the general environment and neighbourhood of subject property)?
  • Have you considered if any of the features are associated for JKW (local water sources/large open spaces/derelict site etc) – in neighbourhood/leaving property/entrance/driveway/parking/ – use online resources or imaging where available? 
  • If recommending treatment, what are the relevant environmental issues?
  • Do you have a working knowledge of what JKW looks like during the season of the inspection? If in doubt – use a smartphone app to assist.
  • Have you recorded all relevant site details in a site record?
  • Have you fully reflected on all potential implications and its impact on the wider market (see 7.2 and 7.3 guidance note)?

Further Information 

If you have any questions on the issues raised in this article, please contact Alex Anderson or Kat Cusack for further information.

The two associations that assist in investigation are: Property Care Association and the Invasive Non-Native Specialists Association (INNSA).  For further information on JKW, visit and the invasive weed control library.

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