Our impact calculator gives indicative valuations only and is not intended as a substitute for taking professional advice from an RICS Registered Valuer with the relevant experience in assessing the diminution in value caused by infestations of Japanese knotweed.
It is recommended that you obtain specific professional advice from an RICS Registered Valuer where you require a valuation upon which you can rely.
RICS Valuers using this tool should note this is an indicative tool only and is not a substitute for exercising their own professional judgement in all cases.
Outputs may vary due to a number of factors outside of the scope of this tool. Specifically, but not exclusively, the tool is not suited where:
Please also note that the extent of knotweed is not easy to determine from visual inspection. Knotweed rhizome may be present underground but not be visible above-ground. Where the extent is estimated this does not necessarily represent site conditions.
Our calculator has been developed by Environet UK Ltd, with assistance from Expert Surveyors Ltd, the leading dedicated provider of RICS expert property valuation reports in the UK.
No responsibility for loss occasioned by any person acting or refraining from action as a result of the use of this tool can be accepted by the authors/developers or Environet UK Ltd.
© Copyright Environet UK Ltd 2025
KnotSure™ is a professional report designed to assess the risk of Japanese knotweed affecting a property within 2.5 miles. It evaluates whether the invasive plant is likely to be present and provides insights into how it could impact the property’s value.