Japanese knotweed
A treatment letter names the house next door. Why must you not file it as treatment of this garden?
Not this garden. A treatment letter that names the house next door must not be filed as treatment of this garden. The address on the letter is the job. A neighbouring house, even one that shares a fence, is a different plot. Filing the letter in this purchase makes it look as if this soil was treated, when the paper says otherwise. The survey of this garden does not borrow next door's contractor. Keep the letter in the file for the house it names, and say plainly that this garden is not that address.
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?
Treatment papers matter only when they identify the land they cover. A letter for next door may show that knotweed was taken seriously on that side of the fence. It does not show herbicide, digging, or a guarantee on your side. Dates, plans and guarantees follow the named property. If the plan in the letter stops at their boundary, it is not a plan of these beds. Do not crop the address off the copy so the letter looks as if it belongs here.
The surveyor can record that you showed them a letter, and that the letter names the neighbour. That sentence is about a document, not about treated soil in this garden. Japanese knotweed must not be spread, which is another reason not to pretend two gardens are one managed area. Ask the seller for papers that name this house, if any exist. If none exist, the honest note is that this garden has no treatment letter, not that next door's letter will do.
What should you ask your surveyor?
- Does any plan in the letter cross the fence into this garden?
- Which address is written on the treatment letter you were shown?
- What did you actually see growing in this garden, as against next door?
What are the typical next steps?
- File the letter against the house it names, not against this garden.
- Ask the seller for treatment papers that name this property.
- Do not tell a lender this garden was treated on the strength of next door's letter.
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
If the contractor treated right up to the fence, does the letter cover you?
No. Cover is what the letter says and which address it names. Next door's letter is not this garden and must not be filed as if it were.
Can the survey rewrite the letter so it applies here?
No. The survey can record the address on the paper. It cannot transfer next door's treatment to this plot or change the house the letter names.