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Japanese knotweed, mortgages & house sales

Finding knotweed doesn't automatically kill a sale or a mortgage. What matters to lenders is how close it is to the property and whether it's being professionally managed. Here's how it really works - and how to keep a sale on track.

Updated July 2026 · 7 min read

Japanese knotweed with yellowing autumn leaves beside a property
Knotweed near a home doesn't automatically stop a sale - how it's managed is what counts.
The quick version: Most lenders will lend on a property with knotweed if there's a professional treatment plan and an insurance-backed guarantee. The old "7-metre rule" was replaced by RICS 2022 risk-based guidance. When selling, you must declare knotweed on the TA6 form - getting it identified and managed early is what protects your sale.

Does knotweed stop you getting a mortgage?

Usually not on its own. Lenders assess each case, guided by a surveyor's report. The key questions are how close the knotweed is to the building, how established it is, and whether there's a credible plan to deal with it. Where a PCA-accredited treatment plan with an insurance-backed guarantee (IBG) is in place, most mainstream lenders are comfortable lending.

The end of the "7-metre rule"

For years, surveyors used a rough rule that knotweed within 7 metres of a building was a serious concern. In 2022, RICS updated its guidance to a more sensible, risk-based assessment: the focus is now on the actual impact on the property - proximity to the habitable structure, evidence of damage, and management - rather than a fixed distance. In many cases this made lenders more flexible, not less.

Selling a house with knotweed - the TA6 form

When you sell, you complete a TA6 Property Information Form, which specifically asks whether the property is affected by Japanese knotweed. You must answer honestly. Knowingly ticking "No" when you know otherwise - or answering "Not known" to hide it - can expose you to a misrepresentation claim after completion, which can be far costlier than the knotweed itself.

The good news: a dated identification and a management plan turn an awkward disclosure into a reassuring one. "Yes, and here's the professional plan and guarantee" is a very different conversation from an unexplained clump found by the buyer's surveyor.

Selling or buying soon? Get a dated, professional confirmation you can hand to a surveyor, solicitor or lender. A photo check plus an accredited surveyor's report gives everyone the certainty they need.

Buying a house with knotweed

Don't walk away automatically - but do go in informed:

  1. Get it identified and surveyed so you know the species, extent and proximity.
  2. Ask for a treatment plan and IBG - ideally arranged (and paid for) by the seller before completion.
  3. Check your lender's stance early; most accept a managed situation.
  4. Factor it into your offer if treatment isn't already in hand.

Get a dated report for your sale

KnotweediD gives a clear verdict in seconds, and for £9.99 a PCA CSJK accredited surveyor can confirm it in writing - a dated report you can share with your solicitor or lender.

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Frequently asked questions

Can you get a mortgage on a house with Japanese knotweed?

Often yes - most lenders will lend where there's a professional treatment plan and insurance-backed guarantee. It's assessed case by case.

Do I legally have to declare knotweed when selling?

Yes. The TA6 form asks about knotweed and you must answer honestly; a false answer can lead to a misrepresentation claim. See more on Japanese knotweed and the law.

How much will treatment cost me?

Typically £2,500-£4,500 (+VAT) for herbicide, more for excavation - see removal costs.

Alexander White, PCA Certificated Japanese Knotweed Surveyor
Written by Alexander White PCA Certificated Japanese Knotweed Surveyor (CSJK) About our surveyors →

This is general information, not legal, mortgage or financial advice. Lender policies and RICS guidance change - always confirm with your surveyor, solicitor and lender, and obtain a survey from a PCA-accredited Japanese knotweed specialist.