The short answer
The 2022 RICS guidance assesses knotweed by risk and sorts each case into management categories A to D, replacing the old fixed 7-metre rule. In broad terms the categories run from the lowest risk (no knotweed on or affecting the property) to the highest (knotweed causing or likely to cause material damage). The category drives the surveyor’s recommendation and how a lender treats the property.
For years, surveyors applied a blunt “7-metre rule”: knotweed within seven metres of a habitable building counted against the property almost automatically. The 2022 RICS guidance note changed that, introducing a risk-based system with management categories. This page explains those categories in plain English, why the change happened, and what each means when you are buying, selling or mortgaging.
RICS categories at a glance
- Framework 2022 RICS risk-based assessment
- Categories A to D, lowest to highest risk
- Replaced The rigid 7-metre rule
- Drives The surveyor’s recommendation and lender view
- Assessed by A PCA-accredited or qualified surveyor
Why RICS moved away from the 7-metre rule
The old 7-metre rule was a crude proxy: it assumed any knotweed within seven metres of a dwelling threatened it. In practice that swept in many low-risk cases and blocked otherwise sound sales. The 2022 RICS guidance note replaced it with a risk-based assessment — the surveyor judges the actual threat to the building, the boundary and value, then assigns a management category.
The categories in plain English
The framework sorts each case by the risk the knotweed poses. Lower categories indicate little or no risk to the subject property; higher categories indicate growth that is closer, more established, or already causing damage and therefore needs active management.
| Category | Plain-English meaning |
|---|---|
| A | No knotweed found within the property’s boundary or affecting it |
| B | Knotweed present but not currently affecting the building — lower risk, manageable |
| C | Knotweed on or near the property warranting a treatment / management plan |
| D | Knotweed causing, or likely to cause, material damage — highest risk |
These are simplified summaries; the surveyor records the precise position and reasoning in the report. The exact wording and boundaries between categories are set out in the RICS guidance and applied to your specific site.
What each category means for a mortgage
- Lower categories generally reassure a lender and may need only monitoring or a light plan.
- Higher categories usually require a documented management plan with an insurance-backed guarantee before a lender will proceed.
- A worst-case category can still be lent against once a credible, guaranteed plan is in place — the category is a starting point, not a refusal.
How the category is decided
The surveyor weighs proximity to the building and boundary, the size and vigour of the stand, evidence of damage, and whether the growth crosses onto or from neighbouring land. That assessment, combined with the recommended action, is what a lender and solicitor read. If knotweed crosses a boundary, the category may also bear on an encroachment claim.
Find out your RICS category
A PCA-accredited surveyor will inspect your property, assign the correct RICS management category and explain what it means for your sale or mortgage.
Frequently asked questions
Is the 7-metre rule still used?
No — the 2022 RICS guidance replaced the fixed 7-metre rule with a risk-based assessment, though proximity still informs the surveyor’s judgement.
Can a high category still get a mortgage?
Often yes, once a credible management plan with an insurance-backed guarantee is in place; the category is a starting point, not an automatic refusal.
Who assigns the category?
A qualified surveyor — usually a PCA-accredited invasive weed specialist — following the RICS risk framework after inspecting the property.
Does a lower category mean I can ignore the knotweed?
Not necessarily; even lower-risk knotweed should be monitored and managed, as it can spread and worsen if left untreated.
Sources & further reading
- RICS — Japanese Knotweed and Residential Property guidance note (2022)
- Property Care Association (PCA) — Invasive Weed Control Group
- GOV.UK — Prevent Japanese knotweed from spreading
This guide is general information, not a site-specific survey or legal advice. Japanese knotweed treatment and removal should be assessed by a PCA-accredited specialist before you act.