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Can you get a mortgage if there is Japanese knotweed?

Image of Michelle Monck

Michelle Monck

Consumer Finance Expert

Japanese knotweed mortgage

At a glance

  • Japanese Knotweed is an invasive plant that can damage your property and reduce its value
  • Mortgage lenders may require evidence of treatment and insurance guarantees before agreeing to a mortgage
  • Removal of Japanese Knotweed is expensive and can take years to remove

Guide contents

What is Japanese Knotweed?

Japanese Knotweed is an invasive plant that was brought to the UK from Japan in the 19th century by a botanist called Phillip von Siebold. He found the plant growing on the side of a volcano and decided to use it in ornamental gardens. It was then sold by commercial nurseries into the 20th century, where it was then used for railway embankments and in areas of mining to help stabilise soil.
Japanese Knotweed evolved to have deep roots to help it survive in Japan where it contends with volcanic, rocky soil, ash deposits and an erratic climate. However, in the UK it was not similarly constrained with its deep roots causing potential issues with foundations, groundworks and drains.
If you suspect you have Japanese Knotweed in your garden, you should seek out a specialist to confirm this – especially because it can be confused with other non-aggressive plants. Getting rid of Japanese Knotweed is extremely difficult and summer is a good time to try to eradicate it before it dies back in the winter.

How does Japanese Knotweed affect me getting a mortgage?

Lenders are concerned about the structural damage that Japanese Knotweed can cause to a property and as a result its saleability in the future. Japanese Knotweed is very aggressive with roots that can cause cracks in tarmac, drains and brickwork. It is difficult to contain as it grows very quickly, up to many centimetres each day and can reach over 2m tall.
The result of actual or potential damage and the limitations then on being able to extend a property or make changes to it all limit the ability of the lender to sell the house if they needed to recover a mortgage debt.

How does a lender look at the risk of Japanese Knotweed?


Lenders want to understand the potential risk of losing their money on a property that could reduce in value due to Japanese Knotweed. They do this through a survey that will document the extent of the Japanese Knotweed infestation and how prevalent the risk currently is. The Royal Institute of Chartered Surveyors (RICS) has a risk assessment framework for Japanese Knotweed and this places properties into four categories:




Japanese Knotweed is within seven metres of the habitable property either in the boundaries or in neighbouring properties or is already causing serious damage to outbuildings, drains and walls, etc.


Japanese Knotweed is present as in category 4 but damage is minor.


Japanese Knotweed is not in the properties boundary but is seen in neighbouring properties. It is within seven metres of the boundary but more than seven metres away from the property.


Japanese Knotweed is not seen on the property but can be seen in neighbouring properties and is more than seven metres away from the boundary.

Those properties falling into categories three and four will need immediate professional help.
Mortgage lenders will decide whether to lend a mortgage on a property with Japanese Knotweed based on the RICS category of the property and the report of the surveyor. They are also likely to want evidence of treatment plans and confirmation that these are funded and have insurance backed guarantees. These guarantees cover the work continuing even if the firm removing the Japanese Knotweed goes bust.
Lenders may decide they will only accept a mortgage with Japanese Knotweed at a certain interest rate or for properties with a minimum level of equity.

How expensive is it to remove Japanese Knotweed?

Getting rid of Japanese Knotweed is expensive, usually costing thousands and even tens of thousands of pounds. For example, physical removal requires the extraction of soil 3m down and 7m across from the edge of visible growth and all of this must be sent to an appropriately licenced waste management facility. Chemical control and eradication are a possibility, but herbicides can take three years to have an effect. And beware even when you think Japanese Knotweed has gone there is the risk that it will return.

Should I speak to a mortgage broker?

Mortgage brokers remove a lot of the paperwork and hassle of getting a mortgage, as well as helping you access exclusive products and rates that aren’t available to the public. Mortgage brokers are regulated by the Financial Conduct Authority (FCA) and are required to pass specific qualifications before they can give you advice.


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Disclaimer: This information is intended solely to provide guidance and is not financial advice. Moneyfacts will not be liable for any loss arising from your use or reliance on this information. If you are in any doubt, Moneyfacts recommends you obtain independent financial advice.

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