Japanese knotweed
What should you ask the seller for if knotweed was treated under a management plan?
Ask for the plan, the surveys, the guarantees and the transfer terms. A sentence that says “it was treated” is not a plan. You want to know what was done, by whom, for how long, and whether the guarantee can move to you.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A management plan usually identifies the plant, maps it, and sets out treatment or removal and the guarantees. The RICS journal’s account of the standard expects specialist advice. It does not say every historic invoice qualifies. Read the exclusions. Disturbing the soil for a patio can void a treatment guarantee. Your solicitor asks the seller. The surveyor, seeing regrowth, will not reconstruct a missing plan.
If the papers show work on the neighbour’s side only, you do not hold that neighbour’s guarantee. If the papers show category-style language from before 2022, ask a specialist whether the plan still matches the growth the surveyor has just seen. Update the lender with documents, not with the seller’s recollection.
What should you ask your surveyor?
- Does what you saw look like regrowth in a treated area, or a separate clump?
- Can you tell from the inspection whether a previous plan is being followed? Usually you cannot.
- What photographs did you take that we should show a specialist?
What are the typical next steps?
- List the documents in the solicitor’s enquiry. No documents means you are buying the growth as the surveyor saw it.
- Ask the guarantee provider, not the seller, whether it transfers.
- If there is regrowth, ask a specialist whether the old plan has failed before you rely on it.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Is a herbicide receipt a management plan?
No. It proves someone bought or sprayed something. It does not prove the plant was identified, mapped and guaranteed.
Should you keep treating it yourself after completion?
Only if you understand the disposal rules and the guarantee. Guesswork spraying can breach the duty not to spread the plant. Government guidance is the starting point.