Getting a mortgage on a property with Japanese knotweed depends on the RICS Management Category the valuer gives it and on the lender's own policy. For Categories C and D, RICS says no retention should normally be imposed. For A and B, it anticipates that most lenders will want a specialist inspection, a management plan and an insurance-backed guarantee.
The 2022 RICS standard
RICS issued Japanese knotweed and residential property in January 2022, and it took effect on 23 March 2022. In October 2022 it was reissued as an RICS professional standard, with which RICS members must comply, and when we checked in October 2026 RICS listed no newer edition. The standard applies to mortgage valuations, and its decision chart is primarily intended for advice to lenders.
It replaced the 2012 RICS information paper, which used four risk categories based on a 7 m distance from buildings and boundaries, a radius taken from the Environment Agency's 2006 knotweed code of practice. The 2022 standard drops the distance-from-buildings test and looks instead at actual impact: damage to structures and the effect on amenity space. The only distance it uses is 3 m beyond the property boundary, for reporting knotweed on adjoining land. RICS based that figure on research by Fennell, Wade and Bacon (2018), which found 3 m a better measure of typical rhizome spread than 7 m.
The four Management Categories
| Category | When it applies | What RICS expects for lending |
|---|---|---|
| A: Action | Knotweed on the property is causing visible material damage to a structure, such as a garage, outbuilding, conservatory, path, or retaining or boundary wall | A retention pending a specialist's report. Most lenders expected to require a specialist inspection and works under a management plan with an insurance-backed guarantee |
| B: Action | Knotweed on the property is not causing that damage, but is likely to prevent use of, or restrict access to, amenity space such as lawns, patios, paths and driveways | The same as Category A |
| C: Manage | Knotweed on the property is neither damaging significant structures nor restricting amenity space | No action and no retention for lending purposes |
| D: Report | Knotweed is not seen on the property but is visible on adjoining land within 3 m of the boundary | No action or retention, except in exceptional circumstances |
Knotweed along a boundary, in boundary hedging or affecting boundary walls counts as on the property. Where knotweed is both on and off the property, the highest on-site category sets the overall result. Knotweed more than 3 m beyond the boundary is normally recorded only in the valuer's notes, unless it is a widespread, mature stand with no sign of management, such as on a derelict site.
Check your likely RICS categoryLender requirements
Categories A and B
RICS anticipates that most lenders will require three things as a condition of the advance, subject to a retention: an inspection by a remediation specialist from a recognised trade body, completion of the recommended works under a Japanese Knotweed Management Plan (JKMP), and an insurance-backed guarantee. The recommendations for A and B are virtually identical, separated only to distinguish damage from impact on amenity space. As of 2022, RICS named the Property Care Association (PCA) and the Invasive Non-Native Specialists Association (INNSA) as the two associations providing this assurance.
A retention is part of the mortgage advance that the lender holds back. How a lender handles one is its own decision, so ask before you commit.
Categories C and D
Under the standard, lenders should treat Category C knotweed like the normal risk from trees and plants, so no retention ought to be imposed. Category D needs no action or retention except in exceptional circumstances, and lenders should not make remediation of a neighbour's knotweed a mortgage condition, because the owner cannot control it.
Lender discretion
The RICS framework is guidance, not definitive. Valuers must use professional judgement and may apply whichever category they consider appropriate. Each lender sets its own policy for each category and can change it, some lenders do not make retentions at all, and when a valuer acts for a lender, the lender's instructions take precedence over RICS guidance. Two lenders may therefore treat the same property differently.
RICS expectations are not lender rules
RICS describes what it anticipates most lenders will do, not what any lender has committed to. Check with the lender directly, or with a mortgage broker, before you rely on it.Insurance-backed guarantees
RICS says a specialist's guarantee typically runs for a minimum of five years after the contract is completed. An insurance-backed guarantee adds an insurance policy that keeps it valid if the contractor stops trading. The guarantee sits within a JKMP, which should include:
- a description and scaled plan of the infestation
- the contractor's details and methods
- a treatment schedule, updated as work is carried out
- a completion certificate after a two-year "no growth" period
RICS adds that lenders take reassurance when the current owner has paid the costs up front, and when the plan transfers to later owners and covers the whole property. Herbicide control needs at least four years of treatment and monitoring before a completion certificate, so plan ahead if you expect to sell or remortgage. Management plans and their guarantees are issued by independent specialists, on terms agreed between you and them.
Lending before 2022
In 2019, under the old approach, the House of Commons Science and Technology Committee found that the seven-metre rule was being used as a "blunt instrument" in some lending decisions, and that some lenders at the time refused, or heavily restricted, lending on affected properties. It concluded that knotweed's physical damage to property is no greater than that of other disruptive plants and trees, though it is particularly hard to eradicate and needs multi-year treatment. The same research by Fennell, Wade and Bacon found that rhizome rarely extends more than 4 m from the plants above ground, and its authors concluded that automatically restricting mortgages where knotweed is present was out of proportion to the risk. RICS now says knotweed rarely causes structural damage to substantial buildings such as houses.
UK Finance, which said it represented 98% of the mortgage lending industry, told the committee in 2019 that for knotweed close to a property lenders would typically expect a full assessment and a treatment programme already started, a transferable, insurance-backed guarantee, funds for the full works paid upfront or held in escrow, insurance in case the firm fails, and work by a suitably qualified firm, usually a PCA or INNSA member. That is history from the old framework, not a statement of current UK Finance or lender policy.
Buying with a mortgage
If you are buying a house in England and Wales, questions 8.6 and 8.7 of the TA6 (6th edition) ask the seller about knotweed, and sellers should attach any survey report or management plan. Ask for both, and if the survey or valuation mentions knotweed, find out which category it falls in.
Tell your broker or lender early, which gives you time to find a lender whose policy fits the property. For Category A or B, where RICS expects most lenders to want a specialist inspection and a management plan, commissioning a specialist survey early avoids delays. Check that the guarantee is insurance-backed and will transfer to you.
Remortgaging
A valuer acting for a new lender should categorise any knotweed they can see. Keep the JKMP, treatment schedule, any completion certificate and the guarantee ready to share. If knotweed is damaging a structure or restricting your garden, get a specialist survey and start a plan before you apply. If the original contractor has stopped trading, check who stands behind your guarantee.
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