RICS on Japanese knotweed

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The Royal Institution of Chartered Surveyors (RICS) is an important trade body in our industry. Their Japanese knotweed information paper is the first cross-industry approved paper to advise Chartered Surveyors on categorising Japanese Knotweed. The paper also highlights approved and recommend methods for removing and treating Japanese knotweed.

The ultimate aim of the paper is to encourage banks to lend on properties that are affected by the invasive weed.

RICS: 5 categories of knotweed severity

The RICS Japanese knotweed information paper categorises the risk caused by Japanese knotweed into five degrees of severity so that banks and other mortgage lenders can make an accurate and reliable decision on how much finance is offered on properties that have a Japanese knotweed problem. The 5 categories of severity are as follows:

  1. No Japanese knotweed is found on the property or those nearby.
  2. There is no Japanese knotweed on the property but it has been found on a neighbouring building or land but it is more than 7 metres away from the boundary.
  3. Japanese knotweed has not been found within the boundaries of the property but it is present on a neighbouring property within 7 metres of the boundary but more than 7 metres from the habitable spaces of the property.
  4. Japanese knotweed has been spotted within the boundaries of the property but it is more than 7 metres from the habitable space. Any damage to outbuildings, paths and fences is only minor. RICS suggest that a Japanese knotweed survey is required.
  5. Japanese knotweed has been spotted within 7 metres of a habitable space at the property. This could either be within the boundaries of a property or in a neighbouring property and/or Japanese knotweed has caused serious damage to outbuildings, paths and boundary walls.

For anything that falls between categories 4-5, the RICS suggest that a specialist Japanese knotweed survey is required. For any Japanese knotweed issue that falls between categories 2-3 the decision to take professional action should be based on a combination of the professional judgement of the valuer and the particular requirements of the client.

Find out more at the RICS website.

RICS Japanese knotweed treatment information

The RICS Japanese knotweed information paper suggests there are 4 different Japanese knotweed removal & treatment methods.

  1. Excavation of the plants and its roots
    The Japanese knotweed infested soil can be excavated and removed to an off-site, licensed, waste-management facility.  
  2. On-site burial and/or encapsulation with membranes
    Japanese knotweed can be buried on-site, however, unless it is covered with 5m or more of overburden a specialist membrane must be installed to encapsulate affected soil to prevent re-growth. The use of an on-site barrier membrane is a popular technique if the Japanese knotweed encroaches onto a neighbours land and they are unwilling to pay for Japanese knotweed treatment.
  3. Biological control
    Biological Japanese knotweed control involves introducing a pest species that will attack and control the Japanese knotweed. This does not completely remove the Japanese knotweed but will keep it at a manageable level. There is a trial currently underway in England using this method.
  4. Chemical control
    The chemical control of Japanese knotweed is when special herbicides are used to treat the Japanese knotweed over several growing seasons. It is usually the cheapest method but can take a number of years to be effective. However, Japanese knotweed guarantees are effective from the day of the first spraying.

To learn more about the treatment methods above, visit our Japanese Knotweed removal & treatment web page.

RICS Japanese knotweed assessment

The RICS Japanese knotweed information paper breaks down the assessment of Japanese knotweed, with regards to its effect on a residential property, into three stages:

  1. The collection of information about the nature and extent of the problem. This information is collected from an on-site Japanese knotweed survey. It can also include a survey of nearby land that is readily accessible or can be viewed from a distance.  A local knowledge check can be used to identify general neighbourhood features which can be associated with Japanese knotweed growth such as the risk of flooding.
  2. Analysis of this information so that the extent of the problem can be established
  3. The use of this assessment as a basis for client advice.


If Japanese knotweed is found on a property then a management plan should be created to deal with the problem. This plan can provide reassurance to lenders and buyers that the Japanese knotweed problem is being managed correctly.

The RICS Japanese knotweed information paper suggests that contractors who are carrying out the Japanese knotweed treatment should have the following characteristics:

  • A transparent fee structure that shows the total cost of treatment before the process begins
  • A contract for the works to be completed
  • An approved Japanese knotweed guarantee or warranty
  • A bond for the warranty to provide protection if the contractor ceases trading during the warranty period
  • A commitment to regular monitoring for and treatment of Japanese knotweed re-growth
  • Annual insurance for professional indemnity cover, employers’ liability cover and public liability cover

What do other authorities think?

The RICS are an important body in our industry but they are not the only ones with information, tips and codes of practice when it comes to Japanese knotweed.

Environement Agency on knotweed

The Environment agency is a government agency concerned with anything to do with the natural world in the UK. They have strict laws and legislation regarding invasive weeds like Japanese knotweed.

Find out more

Property Care Association on knotweed

The PCA is a trade body for the property preservation sector that regulates companies like Wise Knotweed Solutions. They have strict knotweed guidelines that approved companies must adhere to.

Find out more

Contact us about Japanese knotweed

If you suspect that you have Japanese knotweed on your property you can arrange a survey by calling Wise Knotweed Solutions on freephone 0808 231 9218, find your local branch or use our online contact form.

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