Japanese knotweed
Knotweed is growing on the far side of the fence and none was seen in the garden. What can the survey not say about rhizomes under the lawn?
The survey cannot say whether rhizomes run under the lawn. Knotweed was growing on the far side of the fence, and none was seen in the garden. The inspection does not dig, does not look under the turf, and does not map roots it cannot see. No stems on this side is not a finding that the plant stops at the fence. What is known is visible growth next door and a garden surface with no knotweed seen. The ground under the lawn was not investigated.
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?
Knotweed spreads by rhizomes underground as well as by the canes you can see. A fence stops neither. Growth on the far side means the plant is established next door. A lawn with no canes means nothing was visible in the grass on the day. Between those facts is soil the surveyor did not excavate. Saying the rhizomes do not cross would be a guess. Saying they do cross would be a guess of the other kind. The survey's limit is the surface.
A knotweed specialist can advise on the neighbour's stand and on whether investigation in this garden is warranted. The solicitor should see the survey note so the TA form and any seller reply can be compared with visible growth next door, not with a clearance the report never gave. Do not tell a lender the lawn is free of knotweed below ground. The survey did not look there. It saw canes beyond the fence and none in the garden.
What should you ask your surveyor?
- Where was knotweed seen, and where was none seen?
- Did you investigate under the lawn at all?
- Have you avoided saying the rhizomes stop at the fence?
What are the typical next steps?
- Record visible knotweed next door and none seen in the garden.
- Do not claim the lawn is clear below ground.
- Ask a knotweed specialist if you need the rhizome question answered.
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 fence is new, does the fence stop rhizomes?
No. A new fence is a boundary marker, not a root barrier the survey has inspected. Rhizomes are underground. The survey still cannot say whether they run under the lawn. The age of the fence does not answer that question.
Should a specialist, rather than this survey, consider the neighbour's growth?
Yes, if you need more than a surface note. The survey has said what was visible over the fence and what was not visible in the garden. It cannot map rhizomes. That is specialist work, not a rereading of this inspection.