Japanese Knotweed FAQs

Since we launched our Japanese Knotweed Hazard Alert and Insurance Policy, we have been asked a number of questions. We hope you find the below useful. If you have additional questions please do contact us.

As featured in The Telegraph

What data is this new Japanese Knotweed Hazard Alert based on?
The Hazard Alert is based on an exclusive risk model and data from the Centre for Ecology & Hydrology (CEH) and the Botanical Society for Britain & Ireland (BSBI), in association with STL, to assess the probability of the presence of Japanese Knotweed on a property.  It is based on documented instances in an area, and environmental factors determining its distribution. The data covers all of England and Wales, and is updated every six months.

How is the level of risk identified?
The risk model, as above, indicates whether a residential property is a medium or high risk of Japanese Knotweed being present. As an example – if more than two actual instances of Japanese Knotweed have been recorded within 500m of a particular postcode, and there are also a number of environmental conditions conducive to the growth of Japanese Knotweed, then the model would produce a ‘High’ risk Hazard Alert. One example of an environmental factor is – is the property near a railway line? Japanese Knotweed was used to stabilize railway embankments

The Hazard Alert is indicative only and a physical site inspection has not taken place.

Does the Hazard Alert indicate that Japanese Knotweed is definitely present?
No. The Hazard Alert indicates the probability / level of risk only.  The only way to know for certain is for a specialist Japanese Knotweed survey to be conducted on site.

Why would I order an insurance policy if the property is deemed medium risk?
The spread of Japanese Knotweed across England and Wales is nothing less than spectacular. Legislation recognises the impact of this plant:

  • The Wildlife and Countryside Act 1891
  • Infrastructure Act 2015
  • Anti-Social Behaviour, Crime and Policing Act 2014
  • Environmental Protection Act (1990)
  • Law of Nuisance and Third Party Litigation

Japanese Knotweed does and can grow anywhere; it spreads easily and rapidly – it has no county or postcode boundaries. Therefore, every property in England and Wales is at risk of Japanese growing, as reflected in the TA6 question ‘Is the property affected by Japanese Knotweed? (Yes / No / Not Known)’.


What are the Statements of fact for the insurance policy?

  • The property is a single house or flat in England or wales; and
  • The property has existed for the previous 12 month; and
  • The property does not exceed 0.5 acres in size; and
  • Neither the buyer or the seller of the property have any knowledge of any Japanese Knotweed on the property or any adjacent property at or prior to the Inception Date; and
  • Neither the buyer or the seller of the property have conducted or obtained any survey which has shown Japanese Knotweed within 100m of the property; and
  • Neither the buyer or the seller is aware of any on-going Japanese Knotweed treatment or remediation regime within 100m of the property.


Can I buy the insurance policy if Japanese Knotweed is already on the property / on the boundary?
No.  The policy only protects the insured if there is no known Japanese Knotweed at the property when the policy is purchased. If Japanese Knotweed is touching the boundary, we may be able to provide a bespoke policy.

Can I order a Japanese Knotweed Search?’
We do not offer a Residential Japanese Knotweed search, nor does any other search provider. We do, however, provide a unique and free Hazard Alert for residential property transactions, with the option to purchase an insurance policy. 

What if the property being searched is larger than 0.5 acre?
The insurance is valid for properties of up to 0.5 acre. We can supply quotes for larger properties – please contact us.

Does the policy cover developments that will be residential property?
No. The Japanese Knotweed Insurance Policy does not cover residential use or commercial use development sites.

What about Japanese Knotweed and flats?
With upper floor flats, owners will not suffer an infestation in the actual property but they may have to pay towards damage to the main structure or to clear common areas. Does the insurance cover buyers for these indirect problems? If the freeholder requested contributions for the remediation from the leaseholder then the STL policy will cover this should the freeholder request a special contribution and/or within a service charge relating to Japanese Knotweed.

Is there an excess on the Insurance Policy?
No, there is no excess on the standard insurance policy we offer.

Can my client get a survey without taking the insurance policy?
Yes, but it is not a requirement.

Why would my client buy the insurance rather than commissioning a survey?
The cost of an insurance policy is between £50-£60 depending on the risk identified. The cost of a survey varies but will cost more.

The survey will give you a definitive answer as to whether Japanese Knotweed is present on the property. If the survey confirms the plant is not present, the survey will not give any future protection from the plant appearing but, the insurance policy will give protection for 5 years.

If the TA6 form answers ‘No’ or ‘Not Known’ to the question ‘Is the property affected by Japanese Knotweed?’, then the insurance can be purchased. This will protect the buyer for 5 years from Japanese Knotweed subsequently appearing on the property.

What does the Survey Cover?
The definitive presence of Japanese Knotweed can only be determined via a survey conducted on-site. STL, in partnership with the Invasive Non Native Species Association (INNSA) and Japanese Knotweed Solutions Limited (JKSL), offers a comprehensive survey to determine the presence of Japanese Knotweed. This will confirm the exact location and size of any Japanese Knotweed areas. It will also provide details of the methods and associated costs to control and eradicate Japanese Knotweed from the property. The INNSA website provides a comprehensive list of other approved suppliers for Japanese Knotweed Surveys and Remediation Services – www.innsa.org/search-our-members.html

Is the insurance policy accepted by all lenders?
The CLS Risk Solutions Japanese Knotweed Insurance Policy is backed by an AA- Insurer, which is the top of the market, therefore a Lender should have no issue accepting this policy.

How much does a Japanese Knotweed Survey Cost?
We have agreed exclusive pricing with Japanese Knotweed Solutions Ltd (JKSL) from £100 +VAT. There are other companies that specialise in Japanese Knotweed Surveys and Remediation services, see the Invasive Non-Native Specialists Association (INNSA) website for alternative suppliers.