Homes could lose 10% of value because of Japanese Knotweed - claim

A solicitor handling cases involving Japanese Knotweed say the problem could devalue the prices of affected houses by as much as 10 per cent.

Liverpool-based Cobleys Solicitors says the hot weather of the past Easter weekend risks accelerating the spread of the invasive plant species. 

Spokesman Mark Montaldo says: “Usually, we’d only just start to see new knotweed plants emerging late in April or early May, but this year the plants have already grown by a couple of metres. Growth will accelerate as much warmer than average temperatures move in. 

“This is at … one of the busiest times for new houses going onto the market. People are noticing the weeds and are worried about the risk of structural damage and how knotweed can affect their house price.”

The invasive plant can cause damage to homes as it pushes up through cracks in concrete, cavity walls and drains. Cobleys claims that a Japanese knotweed removal firm, Environet UK, estimates that during the past 20 years knotweed has knocked some £20 billion off house prices.

Montaldo says his firm is seeing an increase in knotweed litigation cases due to encroachment. 

“It’s against the law to let knotweed encroach onto surrounding land and property. However, we’re seeing people refuse to treat their own infestations and when it is within seven metres of a neighbouring house, it can start to pose a risk to that house and negatively affect its selling price.

“As this warmer weather is likely to lead to a spread of knotweed, we’d advise people to use this as an opportunity to get outdoors and identify it on their own land and neighbouring properties, and then seek professional support as it’s also illegal to dig up and improperly dispose of knotweed.”

Tell-tale signs include a plant with stems that look like bamboo but are green with purple flecks throughout. It has large, shovel-like leaves that grow yellowish-brown in spring and become a lush green during the summer, with the weed flowering into small white clusters throughout the autumn.

Last year another company - national law firm Stephensons - said that although there were different views over the effect of Japanese Knotweed, people should remain vigilant.

“While the destructive nature of Japanese Knotweed may be unclear, from a legal standpoint it’s much more straightforward. Under the Environmental Protection Act 1990, Japanese Knotweed is classed as ‘controlled waste’ and must be disposed of safely and securely once it’s identified” said a Stephensons spokeswoman.

“Japanese Knotweed is not just a weed or irritant – its presence and spread can be a legal nuisance and a court may decide you have acted negligently in not treating it at all or not treating it correctly. This is in addition to the detrimental effect the plant can have on the value of your property or that of your neighbours” she added.