Japanese knotweed is an invasive plant that continues to cause problems for homeowners, buyers, and mortgage lenders alike. Known for its rapid growth (up to 10cm a day) it can push through cracks in concrete, tarmac, and drains, causing costly damage if not properly managed.
The Royal Institution of Chartered Surveyors (RICS) have published updated guidance for surveyors and valuers in their note ‘Japanese Knotweed and Residential Property’. This guidance aims to help property professionals identify and assess the impact of knotweed more accurately, and it reflects a shift away from the old ‘seven-metre rule’ towards a more practical, risk-based approach.
One key takeaway is that substantial properties with solid foundations, such as most houses, are unlikely to suffer major structural damage. However, outbuildings, garages, conservatories, and garden walls with shallow foundations can be more vulnerable. Surveyors are now advised to flag up knotweed growing on neighbouring land within three metres of a boundary, as encroachment can lead to disputes between neighbours and even legal claims if the plant spreads.
If you’re selling a property where Japanese knotweed is present or even if it has been treated in the past, this must be declared to any potential buyer. Failure to do so could lead to claims for misrepresentation if the issue resurfaces later. Likewise, buyers are strongly advised to insist on professional removal by specialists, backed by a long-term insurance guarantee. While herbicide treatment may control the plant, the only truly reliable solution is full excavation and removal of contaminated soil.
Under government guidance, it is also illegal to cause Japanese knotweed to spread in the wild. Property owners have a legal responsibility to prevent its spread, both on their own land and to neighbouring properties. Allowing it to encroach could result in civil action from affected neighbours.
While the RICS guidance takes a more measured approach, lenders and buyers remain understandably cautious. A property affected by knotweed can suffer a significant reduction in value, and in some cases, buyers may struggle to secure a mortgage at all.
If you’re buying or selling a home where Japanese knotweed is present (or suspect it might be) it’s vital to get legal advice at an early stage. At Frank Smith & Co Solicitors, our experienced Property lawyers can help you navigate the risks, protect your interests, and ensure the right specialist treatment and guarantees are in place.
For more information, please contact Frank Smith & Co Solicitors on 01242 801 748 or visit www.franksmithandco.com.
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