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Fri May 07 2021

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Japanese knotweed code updated

7 Nov 17 A new code of practice has been produced for managing Japanese knotweed.

Gets everywhere
Gets everywhere

The invasive and resilient nature of Japanese knotweed means that it has the capacity to cause extensive damage to properties, road verges, rail infrastructure, flood defences, retaining walls and external works.

The new code of practice replaces the third edition of the Environment Agency document Managing Japanese Knotweed on development sites, which was withdrawn in 2016. The

Invasive Non-native Specialists Association (INNSA) was tasked with producing a new version of the document.

The knotweed code of practice is said to be already the most downloaded document on the Environment Agency’s website.

INNSA chairman James Sherwood-Rogers said: “Expected to be a go-to document for all developers, planners and contractors who may encounter Japanese knotweed in the course of their work, the new Code of Practice will provide a clear understanding of what is required and recommended when managing infested land in an appropriate way.”

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With it now incumbent on any property valuation surveyor to identify and report any Japanese knotweed on the inspected or adjacent properties, the possibility of claims being made is increasing.

This potential for claims was brought in to sharp focus during a landmark court case earlier this year in South Wales. Network Rail was forced to pay compensation to residents after they claimed the encroachment of Japanese knotweed from railway land had damaged their homes and reduced their value.

“Japanese Knotweed presents continual challenges for all segments of the development ecosystem; including local authorities, planners, architects, developers, contractors, consultants and housing providers,” Mr Sherwood-Rogers added.

INNSA’s Code of Practice – Managing Japanese Knotweed is available via

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