Japanese knotweed: what to do and what knot to do

5 June 2018

Japanese knotweed seems to be everywhere nowadays.  Or maybe that’s just how it feels for me since our buyer’s survey revealed Japanese knotweed in the garden. Whilst my use of our garden is largely limited to soaking up the sun, even I knew we were in trouble when I saw the dreaded words “Japanese knotweed” as it can affect property value and makes mortgage lenders nervous. 

What should you do if you discover Japanese knotweed on your property? How do you make sure any property you are buying isn’t affected?  Here are some helpful pointers to make sure you are clear on how to handle this inconvenient invader.

What is Japanese knotweed and why is it such a problem?

When Victorian engineers were designing our railways, they came up with the clever idea of importing Japanese knotweed into Britain. Typically known for colonising volcanoes in Japan, it was introduced to hide, or possibly even stabilise, railway embankments.

Japanese knotweed is now known to be a significant problem across the country.  It spreads quickly and can grow up to 10cm a day between April and October with the roots extending up to three metres deep and up to seven metres laterally.  It is strong enough to break through concrete and can cause considerable damage to buildings and infrastructure.  It’s estimated to be the cause of circa £170 million of home repairs every year and the government estimates that the costs of eradicating it across the UK would be £2.6 billion.

How do I identify Japanese knotweed?

If, like me, you struggle to tell the difference between a weed and a flower then there are plenty of mobile phone apps that will match your photo to their database.  A quick internet search also reveals numerous factsheets with various photos and descriptions to aid the identification process. The simplest way to be on the safe side is to get a specialist to check it out.

What should I do if I have Japanese knotweed on my property?

Do not try and treat this yourself.  Whilst instinct may tempt you to cut it down, Japanese knotweed must be treated at the root and by cutting it down, you could in fact delay the treatment process and may breach strict regulations which control the disposal of knotweed.

Take professional advice on how to eradicate it. Any remedial works must be done by a suitably qualified expert.  Make sure any action taken is covered by an appropriate insurance-backed guarantee which must benefit current and future owners and lenders of the property.

Am I liable for knotweed spreading to adjoining properties?

You must deal with Japanese knotweed straight away.  If you fail to do so then you could be faced with a hefty claim from any adjoining landowner.  This claim could be not just for the costs of removing the knotweed from the adjoining property but also for the decrease in value of the adjoining property. 

In the recent combined cases of Waistell v Network Rail Infrastructure Ltd and Williams v Network Rail Infrastructure Ltd (2017), adjoining property owners succeeded in a claim for nuisance against Network Rail.  The claimants’ properties adjoined a railway embankment owned by Network Rail where Japanese knotweed had been present for many years. The knotweed had spread from the embankment to underneath the claimants’ homes but had not caused any physical damage. The claimants alleged that Network Rail were liable to compensate them for the encroachment of the knotweed onto their land and for the presence of the knotweed, which was an interference with their quiet enjoyment and the amenity value of their property.

Whilst the claimants’ case for encroachment was not successful as there was no physical damage to their properties, they succeeded in their claim for nuisance. The court found that Network Rail had failed to carry out its obligation as a reasonable landowner to eliminate the problem and to prevent interference with the quiet enjoyment of the claimants’ land. The claimants were awarded damages for the cost of treatment programmes and insurance-backed guarantees, the diminution in value of their properties once treatment had taken place and damages for loss of amenity and interference with quiet enjoyment of their property.

This decision was a County Court decision and is thought to be the first decided case on liability for property damage caused by Japanese knotweed. Network Rail is appealing this decision.

A similar decision was reached in the later case of Smith v Line where knotweed was found by the Smiths on property they had acquired from Ms Line. When they discovered the knotweed, the Smiths took action to remove the knotweed from their land and, having successfully eradicated it from their property, requested Ms Line to take action to prevent it spreading back onto their property as it was growing close to the boundary.  Ms Line refused and the judge granted an injunction requiring Ms Line to get a reputable contractor to treat the knotweed on her land and ordered her to pay the Smiths’ costs.

Both of these cases raise the possibility of similar claims being made more frequently in the future. Potential claimants and lawyers alike are eagerly awaiting the outcome of Network Rail’s appeal which is due to be heard by the Court of Appeal later this month.

What should I do if I am buying a property?

Where sellers of existing properties are aware that the property or garden is, or has been, affected by Japanese knotweed, they must declare it on the property information form (known as a Form TA6) as part of the sale process.  However, developers and builders are not obliged to complete this property information form and if you are buying from a developer or builder then you should make sure your solicitor asks specific enquiries to get written confirmation of both the current and the historic knotweed position.

A buyer should always get a survey of the property carried out and should ensure that survey includes the garden and, where possible, gardens of adjoining properties.  This doesn’t apply just to buying a house.  Purchasers of flats should also make sure these areas are covered in their survey since the presence of knotweed could affect the structure of the building and the cost of any remedial works could result in a significant increase in service charge payments.

Can I get insurance against Japanese knotweed?

Whilst most buildings insurers don’t ask about Japanese knotweed, they also may not cover any treatment so check your buildings insurance policy carefully to see if it is covered.  A mortgage lender may also not be willing to lend if the buildings insurance policy won’t cover knotweed.

Indemnity insurance cover can be taken out to provide protection for buyers and mortgage lenders if Japanese knotweed is discovered.  This will generally only be available if no knotweed has been discovered on your property or if it has been successfully treated in the past. This insurance could cover the cost of a survey report to confirm the presence of knotweed, the cost of treatment, repair of any damage caused and could also extend to defending any legal proceedings in the event of any third party being affected.  

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We welcome views and opinions about the issues raised in this blog. Should you require specific advice in relation to personal circumstances, please use the form on the contact page.

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