10-Year Insurance-Backed Guarantees
An insurance-backed guarantee is the document that makes your property mortgageable again. It confirms professional treatment has been completed and protects you — and future buyers — against knotweed regrowth for a full decade.
What Is an Insurance-Backed Guarantee?
An Insurance-Backed Guarantee (IBG) is a formal warranty confirming that a Japanese Knotweed treatment programme has been completed to professional standards by a PCA-accredited specialist. The guarantee is underwritten by an independent insurance company — separate from the treatment contractor — which means you're protected even if the treatment company ceases trading.
The IBG typically runs for 10 years from the date of treatment completion. If the knotweed regrows during this period, the insurer covers the cost of re-treatment at no additional charge to you. The guarantee is fully transferable to subsequent property owners, making it essential for anyone planning to sell their home.
In practical terms, the IBG is what transforms a knotweed-affected property from "unmortgageable" to "mortgage-ready." Without one, most lenders simply won't approve finance. With one, the property can be bought, sold, and remortgaged as normal.
What Your Guarantee Covers
Full re-treatment at no cost if knotweed regrows
Covers any recurrence within the treated area
Guarantee passes to buyers for the remaining term
Long-term protection exceeding lender requirements
Underwritten separately from the treatment company
Compliant with CML and individual lender requirements
Complete paperwork for solicitors and conveyancers
Access to the treatment company for queries throughout
Documentation You Receive
Without a Guarantee
Properties with known knotweed but no IBG are essentially unmortgageable. Most buyers won't touch them, and those who do will negotiate significant price reductions. A 5-15% drop in value is typical.
Why an Insurance-Backed Guarantee Is Essential
Mortgage Requirements
All major UK mortgage lenders — including Halifax, Nationwide, HSBC, Barclays, and Santander — require an IBG before approving a mortgage on a property with knotweed. Some will accept evidence that treatment has started with a guarantee pending, but the IBG must ultimately be provided.
Property Sales & Conveyancing
When selling a property with knotweed history, the IBG is the single most important document your buyer's solicitor will request. Without it, the sale is likely to stall or collapse. With it, the transaction can proceed normally — the guarantee simply transfers to the new owner.
Long-Term Protection
Japanese Knotweed rhizomes can remain dormant underground for years before resurfacing. A 10-year guarantee covers this risk. If the plant does regrow — however unlikely with proper treatment — the cost of re-treatment is covered in full by the insurer.
Company Failure Protection
Unlike a simple company warranty, an IBG is backed by an independent insurer. If the treatment company goes out of business during the guarantee period, the insurance company honours the guarantee in full. This is exactly why lenders require independent backing.
How to Get an Insurance-Backed Guarantee
Get a professional survey
A PCA-accredited specialist surveys your property and creates a treatment plan.
Complete the treatment programme
Follow the agreed plan — herbicide, excavation, or combined approach.
Pass the monitoring period
2+ years of inspections confirm no regrowth from dormant rhizomes.
Guarantee issued
The 10-year IBG certificate is issued once treatment success is confirmed.
The guarantee cost is typically included in the overall treatment price. If purchased separately, expect to pay £500-£1,500 depending on the property and infestation history. See our treatment timeline for the full step-by-step process.
Protect Your Property With a Guarantee
Get connected with a PCA-accredited specialist on the Isle of Wight who can provide professional treatment with a 10-year insurance-backed guarantee. Free survey, no-obligation quote, and a clear path to peace of mind.
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