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Why is Japanese Knotweed considered an implication when buying or selling a house?

16 March 2020

Mark Walton

Japanese Knotweed Damage

Why is Japanese Knotweed considered an implication when buying or selling a house?

Although not poisonous to humans, Japanese knotweed can be harmful to their surroundings. Drawing nutrients and depriving other plants of food, as well as causing damage to properties.

It has been reported that the plant could cover 7 metres in every direction.  It grows roughly 10cm a day but when most prolific, can grow up to 20cm a day. It also has a large root system which can grow down 3 metres.

Despite some misconceptions, it is believed not to grow through concrete. However, it does target weak points or cracks in properties and building structures causing damage as it grows and spreads. Damage to tarmac or paving is commonly associated with Japanese knotweed.

Following a survey, if Japanese knotweed is found on a property, more often than not, mortgage lenders are reluctant to borrow. This is due to the fact that it is difficult to completely eradicate. Not only is it hard to dispose of but can remain dormant for 20 years before rejuvenating. Though some mortgage lenders will consider the application they will usually want to see a professional treatment plan in place with an insurance backed guarantee. 

On average, property owners are facing a 10% decrease in value because of the plant. This is a loss of roughly £22,800 in the UK, which affects between 1% - 5% of homes.

Should you be faced with Japanese knotweed, do not proceed to cut the plant yourself. It is an offence to plant, spread, disperse or allow the dispersal of the plant. You should not trim, cut, flail or chip the plant as any loose fragments can rekindle its growth. Though it is not a legal requirement to report the plant, unlike some other non-native species.  You should immediately contact a qualified professional to assess it and provide an appropriate treatment plan.

This has the greatest effect for a purchaser or seller of a property.  Before proceeding they should consider all the implications surrounding the plant and their individual circumstances. Do you enjoy gardening; therefore, will it be a problem? How soon do you plan to remarket? Will this result in problems with the mortgage lenders or finding a new buyer? Will affect the price of the property? These are some of the questions you need to be asking.

Further, if you left it and spread to neighbouring land, your neighbours may have a claim against you. this could be for the cost of its removal and treatment, the cost of remedial works for any damage that it has caused.  Further, it could be a claim for associated losses for example loss of use of their garden whilst the treatment is undertaken, or reduction in the value of their property.  This is a further reason to treat it once you become aware of its existence.

If you require any advice from our conveyancing or disputes departments please contact our offices on 0114 272 1884 or 01302 341414.