Japanese Knotweed

[Sellinghouse2026]

We have today been advised by our neighbours that the house we completed on the purchase of earlier this year, has Japanese Knotweed in the garden boundary for which the vendors checked the no box on the TA6. We have been told that the neighbours & the vendor shared the cost of the treatment/ management plan however we had absolutely no knowledge of this throughout the conveyancing process & obviously no certification or evidence of the works taking place. I have checked the TA6 (version 2020) and the vendors most definitely ticked no to that question. Can someone please advise me what to do. Thanks so much

The treatment/management plan should have a guarantee so ask solicitors or neighbours for a copy. I sold a house a couple of years ago that had been treated and gave buyers the guarantee. They should have told you.

Have your neighbours got any proof of this? Is it known whose garden the knotweed started in? If its a proper treatment and management plan and shared by both homeowners, I'd assume that the neighbours will have details of who treated it plus payment details and so on. If I had knotweed jointly treated and it was accepted as the responsibility of both neighbours, then if I was the remaining neighbour, I would definitely want proof that it was a joint issue and not just my responsibility. I think you need to do a bit of fact verification as I have outlined before contacting the seller of your house.

You need a copy of the management plan to prove they lied on the form.
And you will have to sue for damages against the vendor.

you need to seek proper legal advice.

Thank you for your responses, our neighbours have said they are willing to share the certificates etc with us

Once you have evidence they deliberately deceived you go to court and sue them for any future related cost associated with the knotweed.

@caringcarerthe treatment plan should include a ten year guarantee so this should be covered.
OP ask your solicitor what steps should be taken.

no need to panic. if the knotweed has been treated and you keep doing the treatments, you will defeat it.

that's great. Hopefully it will indicate that this was a joint problem and your vendor acknowledged that.

Is it still there or was it eradicated?

@Ilovemyshed we are not sure hopefully the paperwork will clarify

From the building side (I've dealt with knotweed on sites over the years): first job is paperwork, not panic digging.

Ask the sellers' solicitors / your conveyancer for the treatment plan, who did the work, and whether there's an insurance-backed guarantee still in force. A proper specialist guarantee is what lenders and future buyers care about. If treatment was done but never declared on the TA6, that's a disclosure issue for the lawyers — I'm not a solicitor, but that file of docs is what they'll need.

Practically: get a PCA-registered (or equivalent specialist) knotweed survey of the property as it stands now. They'll say whether it's still live, how far it extends, and what ongoing treatment looks like. Don't let a general builder "just dig it out" — that can spread it and make things worse.

Until you've got the survey + guarantee position clear, I'd pause any landscaping or digging near the affected area. Once you know the status, you can decide whether it's a claim against the sellers, a top-up treatment, or already sorted under the existing plan.