The history of Japanese Knotweed
Japanese Knotweed is a hardy bamboo like deciduous perennial plant that grows quickly and strongly. It proved very popular with Victorian landscapers, first introduced to the UK in the mid 19th century. Japanese Knotweed was included as a non-native species in the Wildlife and Countryside Act 1981 making it an offence to plant or otherwise cause Japanese Knotweed to grow in the wild. It’s also classified as controlled waste under the Environmental Protection Act 1990.
RICS guidance
The Royal Institution of Chartered Surveyors (RICS) first issued an information paper covering the subject matter in 2012 and have since issued a professional standard in January 2022, ‘Japanese Knotweed and residential property’. The latest guidance stresses the importance of managing Japanese Knotweed rather than focusing on complete eradication. The new guidance has removed the 7-metre rule and placed greater importance on whether the infestation has caused visible material damage to the structure or is likely to prevent use of/restrict access to amenity space. Both circumstances can potentially have a material effect on value. Valuers can reference a decision tree within the latest RICS professional standard to determine the most appropriate recording and reporting of Japanese Knotweed to suit the circumstances. This can range from just making a site note of its presence, through requiring a specialist report, to declining the property as unsuitable security.
Future marketability and saleability
Even if the Japanese Knotweed has been treated and an accredited, insurance backed guarantee has been provided, the stigma of the property having been impacted by Japanese Knotweed previously may still impact future marketability and saleability. This is an important consideration for a surveyor when arriving at an opinion of value. Expertise and knowing the local market really are key here as is knowledge of an individual lender’s guidance which always takes precedence!
Rich Lidsey, Regional Surveying Manager at SDL Surveying
For more information and advice on Japanese Knotweed and other invasive plants click here.