What to do before selling a home with Japanese Knotweed

The threat posed by Japanese Knotweed to your property is often exaggerated. However, the risk posed to the sale of your home is not. The mere presence of this invasive plant, at or near your property, could complicate or even jeopardise the sale of your home.

If you are aware of or have reason to believe there is knotweed in the vicinity of your property, the advice in this article could be the difference between a successful sale and your home suffering a significantly diminished value.

This article also considers the impact of the new guidance issued in 2022.

If you intend to sell your home, here's what you need to do:

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Japanese knotweed

See also: What to check before buying a home with Japanese knotweed

2022 - Japanese Knotweed update

Following a House of Commons report published in 2019, The Royal Institution of Chartered Surveyors (RICS) has published a new 2022 guidance note for chartered surveyors.

The guidance note abolishes the ‘7 metre rule’ used by surveyors and valuers, when assessing whether the presence of Japanese Knotweed poses a threat to a property.

The RICS guidance states that:

“The so-called ‘seven-metre rule’ focused more on what has been demonstrated to be an overstated risk of Japanese knotweed to buildings, rather than its sometimes-serious impact on amenity.”

“Research has demonstrated, and it is now generally accepted, that Japanese knotweed poses little or no risk of structural damage to robust buildings with substantial foundations such as dwellings, as opposed to less sturdy structures with shallow foundations, such as conservatories, garages or boundary walls,”

RICS have moved the dial and are now recommending that, in many situations, effective control can be achieved by the managed application of herbicides.

Valuers and surveyors are encouraged to consider potential Knotweed management outcomes, as opposed to the more rigid building proximity rules.

It is anticipated that mortgage lenders will revise their lending criteria accordingly.

Knotweed and the TA6 Property Information Form

Your conveyancing solicitor will ask you to complete a TA6 Property Information Form. This is a lengthy form that asks questions about your property and how you have used it.

The completed TA6 form will be sent to the buyer's solicitor and will form part of the legal contract of sale.

Since 2013 the form has included the following question about Japanese Knotweed:

"Is the property affected by Japanese Knotweed? Yes, No or Don't know.

Recent updates to the TA6

Following criticism suggesting that the question was too vague (in particular the use of the word "affected'), the TA6 form was updated on 7 February 2020.

The question remains the same, however, the TA6 form has a counterpart set of explanatory notes which have also been updated to include the following clarification:

'The seller should state whether the property is affected by Japanese knotweed. If you are unsure that Japanese knotweed exists above or below ground or whether it has previously been managed on the property, please indicate this as ‘Not known’.'

Note: Solicitors often forget to attach the explanatory notes to the TA6 form, but you can download a specimen copy here:

How should I answer the question on the TA6?

How you answer the question on the TA6 is critical.

The TA6 form still falls short of giving a specific definition of the word ‘affected’. As a seller unaware of the presence of Japanese Knotweed at your property, your default answer might be 'No'.

However, in accordance with the explanatory notes, unless you are absolutely sure there is no Japanese Knotweed, you must answer ‘Not Known’.

If you were to answer 'no', and the buyer subsequently discovered Japanese Knotweed, you would be liable. Unless you plan to carry out extensive excavation works in your garden, the only safe answer is 'not known'.

If you are aware of Japanese Knotweed, your answer must answer 'yes'. The form then states:

If 'Yes', please state whether there is a Japanese knotweed management and treatment plan in place and supply a copy with any insurance cover linked to the plan.

Approved Knotweed management and treatment plans

Specialist companies offer plans for the removal, treatment and maintenance of Japanese Knotweed.

If an approved Japanese Knotweed management plan is not already in place at your property, it might still be possible to start one - even if your home is on the market. You should contact a few companies and ask how long it would take to get a plan underway.

What should I do before putting my property on the market?

There are a number of steps you can take to help prevent the presence of knotweed jeopardising your sale:

There is no legal requirement for you to do anything

The responsibility of managing Japanese Knotweed lies with the owner or occupier of the site of the Japanese Knotweed. There is currently no statutory requirement to eradicate, destroy or report the presence of this non-native species as Japanese knotweed is not currently listed under The Weeds Act 1959.

If you are selling to a cash buyer you could just sell the property as-is. The estimated cost of treatment and removal could be reflected in the asking price.


Japanese Knotweed is a highly invasive plant.

Ignoring the plant will only make matters worse. In order to prevent the rapid spread of this invasive plant, it is recommended to take prompt action to control the spread of the plant. In most cases, the plant, itself, poses less of a threat to a sale than the position of the buyer's mortgage lender.

Most lenders simply won't lend on a property affected by Japanese Knotweed, unless certain criteria are met.

Individual lender requirements are published in the UK Finance Mortgage Lenders' Handbook.

At the time of writing. for example, the HSBC requires any property with Japanese Knotweed within the boundary or on neighbouring land within 7 metres of the habitable space to have:

  • A fully paid up treatment plan which has commenced with an appropriately qualified person or company such as an accredited member of an industry recognised trade association such as the Property Care Association and the Invasive Non-Native Specialists Association
  • A minimum 10-year insurance backed guarantee can be provided on completion of the works.

The solution:

Paying for the treatment plan upfront is within your control. Assuming you can afford to do so (the cost will probably run into thousands), this removes one hurdle for the buyer.

However, it is critical that you check that the Japanese Knotweed specialist you choose can offer a minimum 10-year insurance backed guarantee that starts from the day of the first treatment, rather than the completion of the plan.

Many companies still only offer a guarantee that kicks in at the end of the treatment plan - possibly 3 years in the future. This could scupper your moving plans for the next 3 years.

Case study: The author's personal experience with the Japanese Knotweed and the HSBC

In 2015 I sold my first floor flat in North London. The garden flat below had what can only be described as a sprig of Japanese Knotweed some 8 metres from the property footings.

The plant had been there for an estimated 50 years and had not spread. It was a chance glance over the fence by a neighbour in 2013 that alerted me to the plant's existence. I arranged an immediate survey which confirmed the plant was knotweed.

Thereafter I signed up for a £1,500 eradication program which promised to:

  • Identify any Japanese knotweed at the site/property
  • Assess the scale of the infestation & the properties affected
  • Assess the risk posed to the property/site by any Japanese knotweed
  • Make professional recommendations and offer remedial treatment advice

I then instructed the firm to carry out the treatment plan. The first spray killed the plant and it never returned.

Subsequent revisits confirmed no regrowth and 2.5 years into the 3-year plan I put the property on the market. Despite this immediate treatment success, some 3 years later I almost lost the sale of my flat as the buyer's lender (HSBC) seemed unwilling to lend on it. This would have scuppered the sale and resulted in a catastrophic loss of value in my home.

Passed from pillar to post

The mortgage application was passed around internally as the bank had not designed its processes to efficiently deal with the matter. Solicitors chased constantly but couldn't get a straight answer from the bank.

In the end, I contacted the lender myself and the key issue was an ambiguous word in the small print of the insurance policy. Ultimately I worked with the Japanese Knotweed company to find an alternative suitable policy from another insurer. This process took months to arrange.

£1,500 may seem like a lot to spend on a quick spray of weedkiller - and it is. However, to attempt treatment yourself or to delay the instruction of an approved treatment company would be to miss the point entirely.

What matters is the issue of the indemnity policy. At the time policies were only available on completion of a treatment program. Without this policy, the lender cannot offset the risk and will not see the property as suitable security for the mortgage.

Thankfully I had a program in place and nearing completion at the point of the sale. Nevertheless, the mere mention of the words 'Japanese Knotweed' sent the HSBC into a spin, delaying the sale process by 3 months.

During this time the buyer constantly threatened to pull out and we had no certainty that the HSBC would issue the mortgage offer.

Key steps to take if you think there may be Japanese Knotweed at or near your home:


  • Speak to your neighbours immediately. If the plant has spread to or from their land then any treatment you carry out solely on your property will be a waste of time as the plant must be totally eradicated. Your neighbour will likely be happy to share the cost of the treatment.
  • Get a PCA Certified company to carry out an immediate inspection to confirm that the plant is in fact Japanese Knotweed.
  • Get a quote from 2 or 3 companies - costs vary considerably.
  • Make sure that a suitable 10-year insurance backed guarantee and indemnity policy will be issued at the commencement of the plan. It is critical that this policy is accepted by all major UK lenders.
  • If you are about to go on the market be prepared to pay for the treatment, in its entirety, upfront. Often the lender insists that the plan is paid for upfront as the subsequent owner may not pay for the treatment once they move in and the lender's security will be compromised.


  • Ignore the presence of Japanese Knotweed - the problem won't go away
  • Attempt to remove it yourself. Japanese Knotweed is a notifiable plant and disposing of it through non-formal procedures can incur a fine of up to £2,500 and even earn you an ASBO!
  • Don't cut it, trim it or prune it in any way and don't disturb the soil around or anywhere near the plant.
  • Don't cut the grass or any other vegetation near the plant.
  • Don't spray it with weed killer yourself. There is more to killing it that simply spraying glyphosate. A professional will know the best application method, timing, treatment intervals etc.

See also: What to check before buying a home with Japanese knotweed

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Gaynor Haliday, Legal researcher

Gaynor Haliday, Legal researcher