Introduction
If you’re buying or selling property in the UK in 2025, there’s one leafy menace that could derail the entire deal: Japanese knotweed. It’s invasive, persistent, and still one of the most dreaded words in property circles. But what’s changed recently – and what do you actually need to know this year?
Let’s break it down.
Why Japanese Knotweed Still Matters in 2025
Japanese knotweed (Reynoutria japonica syn. Fallopia japonica) is a highly invasive plant that can damage structures, destabilise land, and drive down property values. Though it doesn’t usually destroy buildings outright, its mere presence on or near a property can:
- Decrease a home’s market value
- Delay or prevent sales
- Impact mortgage approvals
- Lead to legal disputes between neighbours
Even if it’s not causing visible damage, the stigma alone can be enough to spook buyers and lenders.
Legal Obligations: What Sellers Must Declare
In the UK, sellers must disclose the presence of Japanese knotweed via the TA6 Property Information Form, which is part of the conveyancing process.
- If you know your property is affected, you’re legally obliged to declare it.
- If you’re unsure, you must state ‘not known’ but this isn’t a loophole, if knotweed is found it can still come back to bite you.
- Misrepresentation means you knowingly have knotweed but have stated ‘no’ on the property form – this can lead to lawsuits, compensation claims, and delays.
Bottom line: If it’s there, you need to own it – then show buyers you’ve dealt with it properly.
A Supreme Court Twist: Davies v Bridgend Council
A landmark 2023 Supreme Court case has added a new layer of complexity to Japanese knotweed claims.
The short version:
Mr Davies sued Bridgend Council after knotweed from council-owned land spread onto his property, claiming it had reduced his home’s value. But the court denied him compensation.
Why?
- The knotweed had already spread to his land before 2004 – before it was considered an actionable nuisance.
- The court found no evidence that the spread between 2013 and 2018 caused additional harm.
- As such, Mr Davies failed the ‘but for’ causation test – he couldn’t prove the council’s inaction during that period materially harmed his property’s value.
What this means for you:
- Historic spread might not be enough to claim damages.
- You’ll need clear evidence that any recent spread or failure to act caused fresh, measurable harm.
What Mortgage Lenders Expect in 2025
Not long ago, the presence of Japanese knotweed could stop a mortgage dead in its tracks. In 2025, most UK lenders have adopted a more measured approach – but only if there’s evidence that the issue is being handled professionally and thoroughly.
Here’s what lenders typically expect before they’re willing to lend on a property affected by knotweed:
- A professional treatment plan
This must be carried out by a company registered with the Property Care Association (PCA) or the Invasive Non-Native Specialists Association (INNSA). Lenders want to see proof that the infestation is being actively managed. - An insurance-backed guarantee (IBG)
Most lenders insist on a 10-year IBG, which protects the buyer and lender if the knotweed returns. Without this, many mortgage applications will be declined outright. - Surveyor notes or specialist reports
Surveyors play a key role in flagging knotweed risks. If the plant is within 7 metres of the main building or within 3 metres of boundaries or outbuildings, it will almost always trigger lender requirements for further investigation or remediation. - Severity categorisation
Lenders often follow the RICS (Royal Institution of Chartered Surveyors) categorisation system, which assesses the risk level based on the distance and damage caused. Properties in higher categories may be harder to mortgage or require more intensive treatment plans. - Transferable documentation
If the seller has already begun treatment, lenders may still require confirmation that the plan and guarantee are transferable to the new buyer. This is a key point many sellers overlook.
Every lender is different, and some will consider knotweed cases on their own merits. But in general, these steps form the baseline for securing a mortgage on an affected property in 2025.
Example lender policies in 2025:
- HSBC: Will lend if there’s no structural damage and proper treatment with insurance-backed guarantees is in place.
- Nationwide: Requires a professional survey if knotweed is within 3 metres of the house.
- Barclays: Evaluates based on severity category – some cases require mandatory treatment.
- NatWest: Relies on specialist reports to inform lending decisions.
- Halifax & Santander: Vary case-by-case but demand professional input and treatment assurances.
Tips for Sellers & Buyers
Sellers:
- Don’t hide it – disclose it.
- Hire a certified specialist and get that all-important insurance-backed plan in place.
- Keep records of all work done to hand over to buyers.
Buyers:
- Always request a full survey, especially if there’s a risk of knotweed.
- Factor in the cost and timeframe of treatment if you’re proceeding.
- Ensure the seller’s plan is backed by a recognised specialist with a transferable guarantee.
Final Thought: It’s Manageable – If You Act Fast
Japanese knotweed isn’t a dealbreaker in 2025 – but inaction is. Whether you’re buying, selling, or just safeguarding your home’s value, knowing your responsibilities (and rights) is essential.
Treat it, disclose it, and move forward with confidence.
If you’re buying or selling a property get in touch today to book a survey or get expert advice.