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Japanese Knotweed – House sales could be scuppered by alien flora


As if selling a house wasn’t difficult enough with the present state of the property market, a new scare has the potential to stop property sales in their tracks.  

Buyers are pulling out as property survey reports reveal the presence of Japanese knotweed growing in the garden, or even a neighbour’s garden, and lenders are also refusing mortgages.

Some lenders are reluctant because the plant can cause actual, and in some cases, irreparable damage to a property’s fabric. Knotweed is also both expensive and difficult to eradicate in of itself, hence the decision not to lend on properties where it has been found, even if the deterioration is at an early stage.

According to the government’s Environment Agency, Japanese knotweed was introduced into Britain in the 19th century as an ornamental plant. Over time it has become widespread in both urban and rural habitats.

Lenders fear Japanese knotweed causing damage to houses

The plant grows quickly, it can grow a metre or more in a month, and can cause heave below concrete and tarmac, coming up through the resulting cracks and damaging buildings.

Not only is the plant a nuisance, it is actually a criminal offence to allow it to grow and spread (Wildlife and Countryside Act 1981). You could also be liable if it spreads onto your neighbours’ property.

But getting rid of it is not easy, just pulling it up and putting it on your compost heap is not recommended. The weed spreads through its crown, rhizome (underground stem) and stem segments, so leaving even few small remnants in the ground means that it will soon sprout up again.

A 1cm section of rhizome can produce a new plant in 10 days, while rhizome segments can remain dormant in soil for twenty years before producing new plants.

The advice on the Environment Agency’s website suggests that you call in licensed exterminators, but this is likely to be a costly exercise, and not guaranteed to succeed.

House has to be demolished following damage caused by knotweed

In 2011, the Daily Mail reported that a couple in Broxbourne, Hertfordshire, were told their newly-built home had to be demolished as the only way to rid it of an invasion of the weed. It had spread from adjoining land, forcing its way through the walls and flooring of the house and sprouting over skirting boards.

Last month, the Observer reported the case of a homeowner whose sale had fallen thorough because the buyer’s surveyor had spotted a 3cm-high shoot of the weed in the back garden. As a result the buyer could not get a mortgage.

Increasing problems for sellers

Given the plant’s potential to kill property sales, sellers should consider getting their garden surveyed before marketing the property. Often the problem won’t become apparent until a buyer’s survey reveals its existence.

If knotweed is growing on your own property, you can and should take steps to eradicate it.

If it is growing on a neighbour’s land it may be very difficult to get them to take action. You should consider contacting your local council, as well as the local police. Each police force has a wildlife liaison officer who will be responsible for investigating potential offences under the 1981 Act.  

When you are buying, you should ask the sellers whether they have had any problems, and also ask your Conveyancing Solicitor to include a question about this in their enquiries. Fridaysmove can also arrange a survey for you. Call 0800 038 6446 for more information.


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