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9th July 2021

James Letchford discusses commercial properties and the impact of knotweed

James Letchford discusses commercial properties and the impact of knotweed

Guidance on a knotty problem

No one likes Japanese knotweed: it is a particularly pernicious plant as it can cause physical damage to buildings and land and can grow up to 10cm per day during summer months. It usually takes three years to treat Japanese knotweed until the underground rhizomes become dormant – just 0.7g of rhizome left in soil can regrow into a new plant.

The cost and time-consuming nature of dealing with this impacts on the marketability and ultimately value of a property and buyers will reduce their offer or even pull out of a purchase if Japanese knotweed is found.

The Royal Institution of Chartered Surveyors (RICS) has recently published a consultation on draft guidance on Japanese knotweed and residential property in the UK. The consultation closes on 3 August 2021. Whilst the focus of the guidance is focused on surveyors who deal with Japanese knotweed as part of valuations and surveys, it also provides a useful background and summary of the overall problem and how to manage it.

The guidance points out that we now know more about Japanese knotweed and that whilst it is still a challenging issue, too many previous horror stories (or linguistic alarmism as described by a report from the Department for Environment, Food & Rural Affairs) may have meant that the impact in the marketplace is often out of all proportion to the cost of remediation. Further a stigma may remain even where the knotweed has been remediated with a lingering, if diminishing, negative perception and a corresponding adverse impact on saleability.

As the draft guidance notes, brambles can take over gardens if left uncontrolled and gardeners will be used to dealing with persistent weeds such as bindweed. Japanese knotweed rarely causes damage to substantial buildings; it only tends to damage lightweight structures, such as retaining walls, drains and paths. Yet trees and other woody plants can cause more severe structural damage but are not treated in the same way.

As a reluctant gardener who has difficulty in distinguishing between weeds and plants, the fear of having Japanese knotweed in my garden crossed my mind and I have spent some time researching to reassure myself that there are plenty of plants that look like Japanese knotweed but are not. As always, if there is particular concern on a particular property, expert advice should be sought. However, it may be that even if identified, having Japanese knotweed may no longer need to be a death sentence for your English Country garden.

If you are buying or selling a property and are worried about knotweed, or if you have questions about any other commercial property issues, please contact James Letchford on 020 7412 0050 or