Getting a Japanese knotweed survey
What a knotweed survey is for, what you should get at the end of it, what it costs, and how to choose a specialist.
The steps at a glance
Take photos first
Photograph the plant, where it's growing and any nearby walls, paths or boundaries, so you have a dated record before anyone visits.
Ask for the findings and quote separately
Ask for the survey findings and any treatment quote as separate documents, so you can compare before you agree to anything.
Get the scope and price in writing
Before you book, ask what the report will include and what it will cost, and keep their reply.
Arrange access to the whole area
Let the surveyor see every part of your land where the plant is, and ask your neighbour in advance if it looks to cross the boundary.
Keep the report somewhere safe
Store it with your property papers, because you may need it again when you sell, remortgage or talk to a neighbour.
On this page
A knotweed survey is a visit from a specialist who looks at the plant and writes down what they find. It turns “I think that might be knotweed” into something definite you can act on.
You don’t always need one. But when money, a sale or a neighbour is involved, having it in writing makes everything that follows simpler. Our Japanese knotweed overview has the background.
What a survey is for
A survey answers three practical questions. Is it knotweed at all? Other plants can look similar. Where is it, and how far has it spread? And what are the options for dealing with it?
People usually get one for a particular reason. They’ve spotted something in the garden. They’re buying or selling. Or they think it’s coming from next door and want a record before they raise it. Lenders are another reason. If a mortgage valuer finds knotweed that’s damaging a structure or is likely to restrict use of the garden, paths or driveway, RICS guidance expects most lenders to want an inspection by a specialist from a recognised trade body, plus a management plan with an insurance-backed guarantee, as a condition of the mortgage. Each lender sets its own policy, though.
What you should get at the end
You should come away with a written report. HomeOwners Alliance says it should confirm whether knotweed is present, map where it is, assess the risk to the property, boundaries and drains, and recommend a treatment plan. The Property Care Association recommends the map shows how far the roots may have spread underground, not just what you can see. If your lender needs a risk assessment, that should be included too. HomeOwners Alliance puts a survey by a Property Care Association-accredited specialist at from around £250 plus VAT, depending on the property and where it is (2026).
A good report explains what’s there before it recommends anything.
How to choose a knotweed specialist
Many knotweed specialists both survey and treat it. That’s normal, and it’s often what you need: if a lender wants an insurance-backed guarantee, it comes from the firm doing the treatment. What matters is that the findings are clear and you’re free to compare before you agree to any work.
If you’re buying with a mortgage, check what your lender wants first. RICS says that where knotweed is in its Category A or B, most lenders want an inspection by a trade body specialist and a management plan with an insurance-backed guarantee, and that guarantee comes from the firm doing the treatment.
A few plain questions help:
- Will the survey report be separate from any quote? You want the findings to stand on their own.
- Am I under any obligation to use you for treatment? The answer should be no.
- Will any treatment come with an insurance-backed guarantee, and can it pass to a new owner? Ask to see the terms.
- What qualifications or memberships do you hold? GOV.UK names two trade bodies that many knotweed firms belong to: the Property Care Association (PCA) and the Invasive Non-Native Specialists Association (INNSA). RICS guidance names the same two where a lender wants a specialist’s report. For anyone applying weedkiller, GOV.UK also suggests looking for BASIS and Amenity Forum registrations.
Before you agree to treatment, it’s worth getting a second quote.
What you can do before paying for a survey
When a survey is worth paying for
A survey earns its fee when a written record will change what happens next: a sale, a dispute with a neighbour or a decision on treatment. In those cases it’s usually the first thing to get, before any treatment quote.
Sources
- Japanese knotweed and residential property (RICS professional standard, 1st edition), RICS
- Japanese knotweed survey: cost, when you need one and what it involves, HomeOwners Alliance
- How to stop Japanese knotweed from spreading, GOV.UK
- Japanese knotweed, Royal Horticultural Society
Related guides
- Does home insurance cover Japanese knotweed?
Home insurance usually doesn't pay for Japanese knotweed. Here's why, what to check in your own policy, and what you can do before paying anyone.
- What to do about Japanese knotweed from a neighbour
If Japanese knotweed is spreading onto your land from a neighbour's, start with a conversation and a paper trail. Here's how to do that, and when it's worth bringing in a specialist.
- Buying a house with Japanese knotweed (and getting a mortgage)
Knotweed has come up while you're buying a house. Here's what to ask the seller, what a lender may want to see, and how to approach the price.
- Selling a home with Japanese knotweed
You can still sell a home with Japanese knotweed. Here's what you may be asked, what a buyer's lender may want to see, and the paperwork that makes the sale smoother.