Japanese Knotweed Hazards

Japanese Knotweed Hazards

RICS Japanese Knotweed Risk Categories
  1. Japanese Knotweed was not seen on this property, but it can be seen on a neighbouring property or land where it was more than 7 metres away from the boundary.
  2. Japanese Knotweed was not seen within the boundaries of this property, but it was seen on a neighbouring property or land. Here, it was within 7 metres of the boundary, but more than 7 metres away from habitable spaces, conservatory and/or garage of the subject property.
  3. Although Japanese Knotweed is present within the boundaries of the property, it is more than 7 metres from a habitable space, conservatory, and/or garage. If there is damage to outbuildings, associated structures, paths and boundary walls and fences, it is minor.
  4. Japanese Knotweed is within 7 metres of a habitable space,conservatory and/or garage, either within the boundaries of this property or in a neighbouring property or space; and/or Japanese Knotweed is causing serious damage to outbuildings, associated structures, drains, paths, boundary walls and fences and so on.

In this article we will look at category 4 which is the most serious. Below are the most common types of Japanese knotweed damage on a property.

Drain and other buried services

One of the worst types of damage caused by Japanese Knotweed is to service pipes and sewage systems. When there are gaps and cracks within the drainage systems Japanese Knotweed will exploit them and damage the drainage system further resulting in the drains being blocked and having to be renewed which is an expensive repair to carry out.

Patios, Paths and Drives

Japanese Knotweed, like grass, can grow between paving slabs. As with drainage systems it can exploit cracks and further damage the paved areas.

Boundary and Retaining Walls

Garden walls with shallow foundations are susceptible to Japanese Knotweed stands which can exert pressure on them resulting in damage and collapse.


Like boundary and retaining walls, garden sheds and greenhouses are also susceptible to Japanese Knotweed inflicted damage.


These can also be affected by the knotweed as it will infiltrate any path of least resistance. For home buyers, conservatories are a desirable and significant feature of a property.


Well maintained gardens can be ruined by Japanese Knotweed due to its invasive nature.

When dealing with Japanese Knotweed, it’s advisable to enlist a reputable, accredited Japanese Knotweed specialist to deal with the problem. Even a RICS qualified surveyor cannot guarantee to identify Japanese Knotweed and to be absolutely certain if Knotweed is present or not, the best way is to consult a Knotweed Specialist like Japanese Knotweed Ltd to identify and deal with the issue.

Japanese Knotweed Ltd operates nationwide, and are ready to receive your enquiries and undertake site inspections, and provide quotations on request. Call 0333 2414 413 or email contact@knotweed.co.uk for more information.

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