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Portfolio Assessment

Given the increase in claims of Japanese knotweed (knotweed) encroachment and commercial investors, especially institution investors, are deterred from purchasing properties affected by knotweed, it is prudent for property portfolio holders to understand the risk presented by non-native invasive species (INNS).  Richard Newis of AJK has undertaken pre-acquisition due diligence reporting on behalf of some of the UK’s largest property portfolio holders and reviewed the risk to existing assets, from single sites, through to significant property portfolios such as Translink and Ulster Bus in Northern Ireland.

We recently undertook a desk study on 26 properties, on behalf of a Housing Association, and identified 9 of the 26 properties should be surveyed for knotweed.  This is a relatively high percentage for a property portfolio, as typically we see a range of 4% to 7% of properties requiring further investigation.  On surveying the site we will identify which properties are impacted and of those properties which are encroaching onto third party land; where encroachment is from third party land; and where encroachment would be difficult to prove both for the client and third party landowner.  Given that AJK is seeing claims of between £40k and £80k for cases of encroachment, should 9 of the client’s properties be impacted by knotweed and it can be demonstrated by neighbours (potentially three claims per property impacted) that encroachment is from the client’s land, the potential cumulative damages are significant, potentially business ending.  If you manage a property portfolio and want to discuss our services further please feel free to give Richard a call. Continue Reading

Knotweed Encroachment

In recent years there has been a significant increase in claims for Japanese knotweed (knotweed) encroachment onto domestic properties and Richard Newis of AJK has provided expert witnesses reports to court, typically on behalf of defendants.  In the majority of cases we have encountered the claims of encroachment has been based on tenuous evidence, such as a recent project in West Wales.  The contractor advising the claimant had asserted that knotweed had encroached from the defendants land and based on this assertion the claimant employed the services of a solicitor to pursue a claim of over £40,000.  On undertaking a desk study of the impacted area and surveying both properties, it became apparent to AJK that the contractor’s assertions were based on little evidence and we provided our client with a comprehensive report to defend the claim.  Two weeks later our client was advised by the claimant’s solicitors that the claim would no longer be pursued.  If you are defending a claim of knotweed encroachment or misrepresentation during a property sale, which you believe to be incorrect, please feel free to contact AJK for advice.

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The start of 2020 saw severe flooding in the towns and villages of South Wales, including many of our client’s sites and public parks in Cardiff, close to our offices.  Initial surveys undertaken by AJK along the River Taf identified viable knotweed material deposited by the receding waters some 60m from the main river channel!  Areas of complete washout of riverbanks have been also noted during our surveys, however banks impacted by Japanese knotweed appeared to have remained largely stable other than surface erosion.  Therefore we have decided to undertake research on the impact of the recent flooding on the mobilisation of terrestrial invasive species, using our pre-flooding surveys on our Client’s sites and surveys available on public record.  We also want to better understand if invasive species, specifically Japanese knotweed, reduces the risk of bank collapses during these events.

The draft aims of the research project are as follows:

  • Gain a better understanding of the impact of flooding on the mobilisation of invasive species.
  • Estimate the cost associated with invasive species due to flood events.
  • Does the management of Japanese knotweed on riverbanks increase the risk of bank collapse?

If you have any pre-flooding surveys of land adjacent to the River Taf or River Cynon or can provide strong anecdotal evidence regarding new areas of Japanese knotweed and Himalayan Balsam, due to flooding along these rivers, please feel free to get in touch.

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Domestic Review 2019

Ashfield Japanese Knotweed has undertaken a review of our domestic projects in 2019 and identified the following statistics:

On 64% of the properties we surveyed we advised that no further management works were required or advised that a third party land owner was responsible for managing identified Japanese knotweed due to encroachment. This demonstrates the value to Clients of having an independent assessment of the impact of Japanese knotweed at a property, even when a valuation surveyor; contractor; or mortgage provider has recommended further works.

For 35% of the properties we surveyed recommended herbicide management to control the Japanese knotweed at the property and/or to facilitate a mortgage application. On tendering the recommended works we saw an average, saving of £1,600 per property on contractors’ quotes for herbicide projects. As part of our survey costs, where Japanese knotweed management is required, we always tender works to at least three Property Care Association approved contractors on behalf of our Clients.

Only 1% of properties surveyed required excavation of Japanese knotweed and on tendering these works, an average saving of £33,000 per property was identified to the benefit of our Clients.

In conclusion, 2 in 3 properties surveyed by Ashfield Japanese Knotweed Limited resulted in no further works being required. Where further works were required our Clients didn’t have to take the day off work to allow three contractors to the property, to ensure they obtained a competitive quote, we tendered the works on their behalf with savings of between £1,600 and £33,000. We also ensured all works were undertaken by a Property Care Association approved contractor with works supported by a ten year insurance backed guarantee.

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Commercial Development – Norfolk

Sector: Commercial Development

Key Services: Survey, Tender Exercise & Project Management


  • Undertook a survey of the site for the extent of Japanese knotweed.
  • Reviewed existing geo-environmental reporting and identified the risk of Naturally Occurring Radioactive Material (NORM).
  • Submitted a Japanese Knotweed Management Plan to discharge planning conditions.
  • Procured and supervised contractor in the excavation of knotweed & coincidental NORM.


  • Works undertaken on time and within budget.
  • Works approved by both the Local Planning Authority and Radiological Protection Supervisor
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