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Mention the words Japanese Knotweed and many people will shudder with fear.
  • Mar 27, 2020
  • Latest News

They see it as some kind of house-eating triffid that is untreatable and therefore unstoppable.
Japanese knotweed is a fast-growing, bamboo-like plant which was first imported into the UK in the late 19th century and was planted due to its capacity to stabilise the ground through its root structure.


However, the belief that knotweed cannot be eradicated is a major misconception.

Multiple studies have been undertaken in this regard and a paper released a few years ago following the completion of the world’s first extensive Japanese knotweed trial suggested that chemical treatment could be effective.

There is also a widely-held belief that properties are unmortgageable where knotweed is found nearby. This used to be true but, with the spread of knotweed across more areas of the country, this is no longer the case.

Mortgages can be obtained through a variety of mainstream and high street lenders, although it is the case that some will require a survey to confirm the extent of the knotweed growth, and potentially a management plan with an insurance-backed guarantee to be instigated before the monies can be drawn down. In some instances, the cost of treatment may be held as a retention.

With mortgage funding widely available, the impact of diminution in value arising from ‘restricted market appeal’ of a property is significantly reduced, if not totally removed, depending on the alternative properties available to buy at that time.

Despite all of this, ambulance-chasing solicitors and so-called knotweed specialists have over recent years been pursuing claims for tens of thousands of pounds on behalf of property owners affected by the plant.

The claims are for compensation arising from an alleged diminution in value of properties because knotweed has been found on their land, even as little as a sprig.
The trend for claims of diminution in value is growing. The bandwagon keeps rolling.
Claimants often maintain the knotweed has spread to their property from their neighbour’s root structure, but the simple truth is that the plant is everywhere and can be treated effectively and quite easily.
Since the 1981 Wildlife and Countryside Act, it has been an offence to plant Japanese knotweed in the wild.

It’s not against the law to have on your land, but it is not permitted to let it spread beyond your boundary.
I am acting as an expert witness in an increased number of cases on behalf of insurance companies whose clients are property owners facing claims from neighbours because knotweed has spread to their land and they say the value of their homes has fallen as a result.

Some claim they are trying to sell their homes but have been erroneously told by their estate agent that they cannot put the property on the market because no-one will buy it. This may not be the case.
Others are simply panic-stricken because of the hysteria about knotweed in the Press.

My instructions mainly come from solicitors representing insurers. The cases span the country, from the north west to the south coast, and defendants include homeowners, schools and large companies and organisations.

Many cases end up in court and I have extensive experience in such matters, often helping to substantially reduce the value of claims arising from knotweed.

To those with knotweed on their land, my message is: Don’t panic. It’s not as bad as it is made out to be. It can be easily controlled and in most cases eradicated by a chemical treatment programme.
There are some genuine claims, from people with knotweed that has spread from next door and who face costs to remove it or treat it properly.

The issue is the level of the claim. I believe the sum is often vastly inflated because of the hysteria surrounding knotweed, and the fact that people get worked up into an emotive state, suggesting excavation of the plant and the ground around it.

Yes, this may be necessary in extreme circumstances, but it is not the case for the majority of cases in which I have been involved. A chemical treatment programme with a 10-year insurance-backed guarantee may be possible for as little as a few thousand pounds.

In many cases I have viewed, the reason a property’s value is diminished, or a sale cannot take place, is due to poor maintenance of the property itself, not because of the knotweed.
In my experience, the upper levels of claims, which can range from £10,000 to £80,000, are rarely upheld.

Yes, Japanese knotweed is an undesirable plant, but it can be controlled or eradicated over a period by chemical treatment, while in the worst of circumstances it can be dug out and removed. It’s not the end of the world.

Neil Inman is a partner at surveying and property management firm Scanlans and heads the Birmingham office.

Scanlans is a national practice with offices in Manchester, Leeds and London as well as Birmingham. Neil joined Scanlans in 1988 and established the Birmingham office in 1995.
He has been actively involved in the valuation of all types of residential and commercial property for nearly 25 years.

Neil also has extensive experience of preparing expert reports for property and land valuations, diminution of value cases involving Japanese knotweed and neighbour nuisance matters, boundary disputes, landlord and tenant disputes and compulsory purchase compensation.
Through these, he has experience of mediation and court appearances. He also provides development advice for residential and commercial opportunities, and he gives consultancy advice to banks for valuation audits.

Neil has a host of professional accreditations and qualifications to his name.
He has been a professional associate of the Royal Institution of Chartered Surveyors since 1992. He is a fellow of the Association of Property and Fixed Charge Receivers, a Registered RICS Fixed Charge Receiver and a RICS Registered Valuer. He is also a member of the Association of Registered Letting Agents, now known as ARLA Propertymark.