The short answer
An insurance-backed guarantee (IBG) is an insurance policy that funds re-treatment of Japanese knotweed if it regrows and the original contractor has ceased trading. It sits behind a PCA-accredited contractor’s own guarantee, typically runs 5–10 years, and is transferable to future owners. Lenders want an IBG because it protects their security for the whole mortgage term, not just the treatment period.
A contractor’s guarantee is only as good as the contractor. If the firm that treated your knotweed goes out of business and the plant returns, an ordinary guarantee is worthless. An insurance-backed guarantee solves that problem – and it is the single document, alongside the treatment plan, that most lenders insist on. This guide explains what an IBG covers, why lenders care, and what to check before you rely on one.
The IBG at a glance
- What it is Insurance behind the contractor’s guarantee
- What it covers Re-treatment if contractor fails
- Typical term 5–10 years
- Who issues it Via PCA-accredited contractors
- Transferable? Usually yes, to new owners
- Why lenders want it Protects security long-term
What an IBG actually covers
A PCA-accredited contractor gives a guarantee on its treatment – for example, that it will return to re-treat regrowth within the guarantee period at no extra cost. The insurance-backed guarantee is a separate insurance policy that steps in if that contractor can no longer honour its guarantee, typically because it has gone out of business or become insolvent. The IBG funds the cost of bringing in another firm to complete or repeat the treatment. It backs up the workmanship guarantee; it is not a general property insurance.
Why lenders insist on it
A mortgage can run for decades. A treatment programme and a contractor’s guarantee might cover only a few years. The lender’s security – the house – needs to be protected for the whole term, even if the contractor disappears. The IBG bridges that gap, which is why the UK Finance Mortgage Lenders’ Handbook framework leads most lenders to require one before lending on an affected property. Pair it with a credible plan and you have what is needed to get a mortgage on a knotweed property.
| Feature | Contractor guarantee | Insurance-backed guarantee |
|---|---|---|
| Who pays for re-treatment | The contractor | The insurer, if contractor fails |
| Survives contractor insolvency | No | Yes |
| Typical term | Linked to treatment | 5–10 years |
| Accepted by lenders | Not on its own | Yes – usually required |
What to check before relying on one
- The IBG is arranged through a PCA-accredited contractor and underwritten by a recognised insurer.
- The term (commonly 5–10 years) and exactly what triggers a claim.
- That it is transferable to a buyer if you sell – lenders and buyers will want this.
- That the underlying management plan is documented and the treatment is being carried out as specified.
How to get one
You obtain an IBG by commissioning treatment from a PCA-accredited contractor that offers insurance-backed guarantees; the IBG is arranged alongside the treatment plan. When selling, having the plan and IBG in place before marketing keeps the buyer’s lender on side. This is general information, not legal or financial advice – confirm details with the contractor, insurer and your conveyancer.
Need an IBG to satisfy a lender?
Use a PCA-accredited contractor that offers insurance-backed guarantees. The IBG is arranged with the treatment plan and is what most lenders require to proceed.
Frequently asked questions
Why do lenders want an insurance-backed guarantee?
Because a mortgage can run for decades while a contractor’s guarantee might cover only a few years. The IBG funds re-treatment even if the contractor goes out of business, protecting the lender’s security for the whole loan term.
How long does an IBG last?
Typically 5 to 10 years, depending on the provider and the treatment. Always check the exact term and what triggers a claim before relying on it for a mortgage or sale.
Is an IBG transferable when I sell the house?
Usually yes. A transferable IBG is important because the buyer’s lender will want the protection to continue. Confirm transferability with the contractor and insurer, and pass the documents to the buyer’s conveyancer.
Is a contractor’s guarantee the same as an IBG?
No. A contractor’s guarantee depends on that firm still trading. An IBG is a separate insurance policy that pays for re-treatment if the contractor fails. Lenders generally require the insurance-backed version, not the contractor guarantee alone.
Sources & further reading
- Property Care Association (PCA) — Invasive Weed Control Group, insurance-backed guarantees
- UK Finance — Mortgage Lenders’ Handbook
- RICS — Japanese knotweed and residential property, guidance note (2022)
- 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.