UK warning as Japanese knotweed can knock £13.5k off house value

Amid a surge in Japanese knotweed spreading rapidly across the UK, a property expert has warned that tackling the plant yourself could land you a £5k fine or imprisonment.

Jack Malnick, Managing Director of Sell House Fast, said: “Japanese knotweed is one of the UK’s most problematic weeds that can spread up to seven meters long, take up to three years to treat and can drastically reduce a property’s market value.

“Even if treated, this highly invasive plant can still deter potential buyers. It may be tempting to cut costs and remove knotweed yourself, but this could have disastrous consequences for your property value as well as impact your finances and your legal situation.”

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Mr Malnick added that homeowners should avoid DIY removal and prepare to pay up to £5k.

“It is advised not to attempt a DIY removal, due to the environmental restrictions for disposal,” he said.

“Removal costs depend on the size of the infestation, treatment method, and site access.

“The average cost of knotweed removal is between £1.5k and £2k, but a full evacuation can cost up to £20k.

“The UK average house price is currently around £270,080.

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“Estimates from Environet suggest Japanese knotweed can reduce property values by at least 5 per cent, meaning that homeowners could, at best, lose around £13,504 in value alone.

“However, with potential treatment costs of up to £10k or more for severe cases, early treatment is usually far cheaper than leaving the infestation unmanaged.

Wrong disposal could land you a £5K fine or imprisonment, as Mr Malnick added: “Improper disposal of invasive species such as Japanese Knotweed is not merely reckless; it is a criminal offence.

“The Wildlife and Countryside Act 1981 makes it an offence to plant or cause Japanese knotweed to grow in the wild.

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“Offenders may face fines of up to £5k and/or six months’ imprisonment, or on indictment, up to two years’ imprisonment and an unlimited fine.

“Government guidance says that the plant must be transported only to specially licensed landfill or incineration facilities authorised to handle hazardous invasive waste.

“Failure to do so risks not only environmental pollution but prosecution under UK law.

“If Japanese knotweed from a neighbouring property spreads onto your land, you are not liable. In fact, you may be entitled to claim damages.”

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According to a key Court of Appeal ruling, it was confirmed that landowners can be held responsible for allowing Japanese knotweed to spread.

You can also pursue compensation for loss of value and the cost of removal, and claims may still succeed even where knotweed has been present for many years.

“Start by raising the issue with your neighbour, explaining their liability and ensuring they carry out professional removal,” added Mr Malnick.

“If your neighbour is uncooperative, you can contact the council’s Japanese knotweed team or environmental services to escalate the issue.”