Japanese Knotweed is a plant that can cause havoc when buying and selling property. Find out more about this species and the implications if it is found in or around a home.  

What is Japanese Knotweed? 

Japanese Knotweed (Fallopia Japonica)  is an invasive, non-native species of plant. It is a very aggressive weed with bamboo-like stems and white flowers. It lies dormant through the winter months and then grows rapidly in spring. 

The plant can grow by 30cm in a single week and reach a height of 2m above the ground. But it’s underground that it does the most damage. Its roots can damage foundations, drainage systems and walls – if left, it can make a house very difficult to sell. 

A further challenge is that when Knotweed appears to have been dealt with, it can split and grow back. It can be a big problem when building an extension or conservatory or laying a patio, because digging through a dormant root can kickstart regrowth. 

Can Japanese Knotweed stop you getting a mortgage? 

Many mortgage lenders won’t lend on a property with Japanese Knotweed, because of the potential damage to the building. Some providers will allow you to borrow, depending on the severity of the problem and whether it’s under effective control. 

There are five categories of Knotweed invasion, ranging from One – where there is no Knotweed present, to Three – where it is in neighbouring properties but not within your boundary, through to Five – where it is close to the property and causing damage. 

If the property is in categories two or three, lenders want to make sure that you’re aware of the Knotweed, and will ask you to sign to confirm.

Do surveyors check for Japanese knotweed?

Surveyors are trained to spot the signs of these invasive plants, which have distinctively shaped leaves. It will grow in the wild, especially on river banks, and can cross into the boundary of a property. 

If knotweed is flagged up on a survey, the mortgage lender will typically ask for a specialist report to be commissioned at the expense of the seller. The report categorises the risk to the property on the RICS scale and details options for controlling Japanese Knotweed.  

Do sellers or estate agents have to disclose Japanese knotweed?

The seller of a property is legally obliged to declare if Japanese Knotweed is on the land. Your estate agent should be aware too – and if either party knows that this invasive weed is present but doesn’t disclose it, they could be sued. 

If the plant is present, an estate agent should advise the seller to appoint a specialist company to eradicate Japanese Knotweed. They will provide a warranty for completed work that is protected by an independent insurer. The property owner also needs to advise the Environment Agency that the plant has been detected.

How much is it to remove Japanese knotweed?

The cost depends on the method of weed control used and the severity of the infestation. Even a small area of the weed can cost several thousand pounds to clear, as the stems must be disposed of at a licensed landfill site. A large infestation could cost more than £30,000 to treat.

Is Japanese knotweed removal covered by home insurance?

Most buildings insurance policies won’t cover damage caused by Japanese knotweed. If the Knotweed is on your land, insurers tend to assume there’s been a lack of property care – because you haven’t taken steps to protect your home. 

You’re unlikely to be able to claim for removing knotweed unless you take out a specialist Japanese knotweed insurance policy before the plant is spotted near your property. 

How can a Mortgage Broker help?

While we can’t specifically help you manage the Knotweed infestation, we can certainly explain the options that are open to you, whether you already own the affected property or it’s on a property that you’re considering buying. 

Japanese Knotweed won’t necessarily mean you can’t buy or sell a property – it’s a question of getting good advice, taking the right steps and talking to an experienced broker for support.  

Getting a mortgage or remortgage is not impossible, especially once the problem has been treated. You might need to take out certain insurance to qualify for a mortgage deal. We’re here to help you with advice and support at every step.