The rise in Japanese knotweed surveys: Why sellers and buyers are seeking certainty

Knotweed surveys are increasing in the UK property market

Japanese knotweed is no longer just an environmental issue, or property concern: it is a legal, financial and conveyancing risk.

• Mortgage lenders may refuse to lend without evidence of management

• Sales can fall through due to uncertainty or poor disclosure

• Misrepresentation claims (where knotweed is failed to be reported by either the seller or the surveyor) can cost thousands in compensation

As a result, both buyers and sellers are becoming more savvy – knotweed surveys are moving from reactive to preventative. 

The new TA6 Form: Why “No” requires absolute certainty

One of the biggest drivers behind this trend is the TA6 Property Information Form. This document is mandatory – required to be completed by sellers in England and Wales to provide crucial details about a property to potential buyers. The new edition - updated on 30 March 2026 covers boundaries, disputes, alterations, parking, and environmental factors like flooding and energy efficiency – it also covers Japanese knotweed. When selling a property, you must declare whether Japanese knotweed is present. However:

• You can only answer “No” if you are certain no knotweed exists on or near the property

• This includes within 3 metres of the boundary, even below ground

The big challenge: Most homeowners are not qualified to identify knotweed rhizomes underground. 

The risk of guessing!

Many sellers assume: “I’ve never seen it, so I’ll tick ‘No’” but this is where problems arise.

• Incorrect answers can lead to legal claims for misrepresentation

• Buyers can claim for treatment costs, loss of value, and legal fees

• Issues are often discovered after completion, when it’s too late to renegotiate

A new seller mindset: Confidence beats assuming

Property is probably the most expensive purchase anyone will make, so any risks associated with that must be addressed not ignored. This is why more sellers are now searching:

• “How can I prove there is no knotweed on my property?”

• “Do I need a knotweed survey before selling?”

• “Can I be sued for knotweed after sale?”

The simple answer is to get a professional survey. A specialist knotweed survey provides a comprehensive report that allows sellers to:

• Confirm presence or absence – and crucially – with evidence

• Accurately complete the TA6 form

• Provide reassurance to buyers and lenders

• Avoid delays, renegotiation, or legal disputes

As guidance highlights, answering “No” requires complete certainty, not assumption. 

Buyers are driving demand too: They’re increasingly requesting a knotweed survey

It’s not just sellers – buyers are also pushing this trend.

Searches like these are increasing as awareness grows:

• “knotweed survey before buying house”

• “should I get a knotweed survey UK”

• “knotweed found after purchase what can I do”

Buyers are becoming more cautious because, with plenty of knotweed information to hand, they know:

• Knotweed can affect mortgage approval

• It may reduce property value

• It can lead to unexpected remediation costs

• Standard surveys may not fully assess invasive species risk

For these reasons, in many cases, lenders or surveyors will recommend a specialist knotweed report before exchange. 

“Not known” is no longer good enough

Another growing trend is sellers answering “Not known” on the TA6 form.

While this avoids immediate liability, it often:

• Raises red flags for buyers

• Triggers further investigations

• Causes delays in conveyancing

• Leads to renegotiation or buyer withdrawal

In reality, “Not known” often results in the buyer commissioning a survey anyway which inevitably slows the process up – increasing the risk of conveyancing failure. As anyone knows who’s bought or sold a house – sales can easily break down – nothing is certain until final exchange of contracts and even then buyers can still pull out. 

The commercial impact: Speed, certainty and value

For both parties, the benefits of a knotweed survey are clear:

For sellers

• Confidence to tick “No” correctly on the TA6 form

• Reduced risk of legal claims

• Faster, smoother transactions

• Stronger negotiating position

For buyers

• Clarity before committing

• Reduced risk of hidden costs

• Better mortgage outcomes

• Peace of mind

Why this trend will continue

Several factors are driving continued growth in knotweed surveys:

• Increased legal awareness around misrepresentation

• Greater lender scrutiny

• More educated buyers

• Seasonal visibility issues (knotweed dies back in winter)

Put simply: Uncertainty is now seen as a risk and surveys remove that uncertainty. 

Final thoughts: Certainty is the new standard

The UK property market is changing – people are more aware of the risk of ignoring knotweed, and how to overcome those risks. Where once sellers might have relied on assumption, today’s approach is:

• Evidence over guesswork 

• Transparency over risk 

• Professional surveys over uncertainty

For sellers, the goal is simple: Be confident when ticking “No” on the TA6 form – not hopeful. For buyers, it’s about: Knowing exactly what you’re purchasing before you commit, and enabling positive loan outcomes. If you’re thinking of buying or selling a property in the UK – it's best to be proactive and book a survey.

This article was written and supplied by Japanese Knotweed Limited.