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How Much can Japanese Knotweed Devalue a Property?
Japanese knotweed and house prices
It’s a question we’re often asked, and the answer is – it depends! So we’ve teamed up with Expert Surveyors Ltd, the leading dedicated provider of RICS expert property valuation reports in the UK and created a valuation impact model that gives indicative price reductions.
How does Japanese knotweed affect house prices?
Japanese knotweed is an invasive plant species that poses significant challenges for homeowners and property sellers in the UK. Its rapid growth and ability to cause structural damage make it a serious concern for mortgage lenders and buyers alike. Below are the key ways Japanese knotweed can affect property values and marketability.
Treatment costs
Japanese knotweed is notoriously difficult to eradicate. Professional treatment programmes can range from £2,000 to over £20,000, depending on the extent of the infestation and the method of removal. Mortgage lenders often require a formal treatment plan with an insurance-backed guarantee before approving a loan, adding to the overall cost.
Stigma and inconvenience
The presence of Japanese knotweed carries a strong stigma. Many buyers are hesitant to purchase a property with a known infestation, fearing structural damage and future growth. This can significantly reduce the pool of potential buyers, making it harder to sell.
Resale value
Properties affected by Japanese Knotweed often suffer a 10–15% reduction in market value. Even after successful treatment, the history of infestation can deter buyers and affect price negotiations. Some sellers may have to accept lower offers or wait longer to find a willing buyer.
FAQs
- Most lenders want to see a managment plan in place from a professional
- Most will also require the work to have an Insurance-backed Guarantee (IBG)
- Read our guide to Japanese knotweed and motgages here
- Our 2024 YouGov research revealed that a third of all buyers would simply walk away from a property affected by knotweed
- It also revealed that most others would look for significant price reductions
- Read our guide to buying and selling here.
- In legal cases, damages are awarded to cover the cost of treatment/removal
- They also include diminution in value, the blight caused from the risk of knotweed re-growing
- Read more about Japanese knotweed and the law here
KnotSure gives an indicative valuation and includes revised valuations for the property if it has the benefit of a 10-year IBG following either herbicide treatment or physical removal.
For high-value properties the extra cost of physical removal over herbicide treatment is often justified on purely economic grounds, when the residual diminution is considered. Removing the problem minimises the blight.
Actual market price, as opposed to a valuation, is the price that a willing buyer and a willing seller agree to – they are not necessarily the same!
Useful information
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If you already know you have an invasive plant problem, you can request a survey online in less than two minutes by providing a few brief details. A member of the team will swiftly come back to you with further information and our availability.
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Simply upload a few images of your problem plant to our identification form and one of our invasive plant experts will take a look and let you know, free of charge what you are dealing with. We’ll also be there to help with next steps where necessary.
