Japanese knotweed survey
Japanese knotweed can damage structures and is notoriously difficult to get rid of. If it’s suspected on a property you’re buying, selling or building near, mortgage lenders will usually want a survey and a management plan from a specialist before they’ll lend.
This guide covers the rules in England. See Wales, Scotland and Northern Ireland.
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Why it matters to a sale
Most mortgage lenders follow guidance based on how close knotweed is to habitable space and other structures. Depending on the extent and proximity, a lender may ask for a management plan with an insurance-backed guarantee before releasing funds, or in severe cases decline to lend until it’s treated.
How treatment works
- Herbicide treatment typically runs over 2–3 growing seasons to fully kill the rhizome
- Excavation and removal is faster but more disruptive and expensive, and still needs careful disposal as controlled waste
- A completed treatment plan usually comes with an insurance-backed guarantee that reassures lenders and future buyers
In Wales, Scotland and Northern Ireland
This guide describes the rules in England. Building regulations are devolved, so here is how japanese knotweed survey works in the rest of the UK.
The same legal position and PCA-accredited treatment approach applies across Wales.
The same legal position applies in Scotland; the Wildlife and Countryside Act provisions on spreading knotweed into the wild cover Scotland too.
The same legal position and treatment approach applies in Northern Ireland.
Common questions
Is it illegal to have knotweed in my garden?
No, but it is an offence to allow it to spread into the wild, and causing it to spread onto a neighbour’s land can lead to a legal claim against you.
Can I just dig it out myself?
It’s very easy to spread fragments and make the problem worse. Disposal also counts as controlled waste, so DIY removal is generally not recommended.
How much does treatment cost?
It depends on the size of the infestation and whether you choose herbicide treatment or excavation. Get a specialist survey first for an accurate plan and quote.
Will it stop my house sale?
Not necessarily, but most lenders want evidence of a management plan or completed treatment with a guarantee before they’ll lend, so it needs addressing early in the process.
New to the jargon? See our glossary of terms, from air permeability to TrustMark.