The short answer
A herbicide programme typically costs £1,500–£3,000 over around three seasons; full excavation runs £5,000–£15,000 or more. A survey or report adds roughly £150–£350, and an insurance-backed guarantee (IBG) — often required by mortgage lenders — adds a further fee. The biggest price drivers are the size of the stand, access for machinery, how the waste is disposed of, and whether you need fast results for a sale or development.
Cost depends entirely on the method, the size of the infestation and the disposal route, so any honest figure is a range rather than a single number. Below is a breakdown of the typical components — survey, herbicide, excavation, on-site relocation and the insurance-backed guarantee — with the factors that push a quote up or down.
Removal cost at a glance
- Survey / report £150–£350
- Herbicide programme £1,500–£3,000
- Excavation £5,000–£15,000+
- Insurance-backed guarantee Additional fee
- Main price driver Size, access & disposal
The cost components
A typical knotweed project has up to five cost lines. Not every project needs all of them — a small garden stand with no sale pending may only need a survey and a herbicide plan.
| Item | Typical UK range | Notes |
|---|---|---|
| Survey / report | £150–£350 | Identifies extent; needed for a plan |
| Herbicide programme | £1,500–£3,000 | ~3 seasons + monitoring |
| Excavation (dig-and-dump) | £5,000–£15,000+ | Driven by landfill / waste cost |
| On-site relocation / bunding | Varies | Burial or screening on the same site |
| Insurance-backed guarantee | Additional fee | Often required by lenders |
What drives the price up
- Size and density of the stand — more rhizome means more herbicide seasons or more soil to remove.
- Access — if an excavator cannot reach the stand, costs rise sharply.
- Disposal route — knotweed soil is controlled waste; licensed landfill is the most expensive option. On-site burial or screening, where space allows, can be cheaper. See disposal rules.
- Urgency — needing it gone for a sale or build pushes you towards costly excavation rather than a slow herbicide plan.
The insurance-backed guarantee (IBG)
Most mortgage lenders will not lend on a property with knotweed unless there is a documented treatment plan backed by an insurance-backed guarantee from a PCA-accredited contractor. The IBG ensures the work is honoured even if the contractor ceases trading. It adds cost but is frequently essential for a sale or remortgage — see our notes on the management plan and lender expectations.
How to get an accurate figure
The only way to get a real price is a site survey: the contractor measures the stand, checks access and disposal options, and quotes against a chosen method. Compare like-for-like quotes — herbicide against herbicide, excavation against excavation — and check each includes disposal and any guarantee. For the underlying methods, see how to kill knotweed.
This page is general guidance, not a quote. Figures are typical 2026 UK ranges and your site may differ.
Get a real quote, not a guess
A survey converts these ranges into a firm figure for your site. Ask a PCA-accredited contractor to quote herbicide and excavation so you can compare like for like.
Frequently asked questions
Is herbicide or excavation cheaper?
Herbicide is almost always cheaper — typically £1,500–£3,000 over three seasons against £5,000–£15,000+ for excavation. Excavation costs more because of machinery and the high cost of disposing of controlled waste at licensed landfill.
Why do quotes vary so much?
Price is driven by the size of the stand, access for machinery, and the disposal route. A small accessible garden stand treated with herbicide sits at the bottom of the range; a large stand needing dig-and-dump to landfill sits at the top.
Do I need an insurance-backed guarantee?
If you are selling or remortgaging, almost certainly. Most lenders require a treatment plan with an IBG from a PCA-accredited contractor before they will lend on the property.
Can I reduce the cost?
Sometimes — choosing a herbicide programme over excavation, or burying treated soil on site rather than sending it to landfill where space and the survey allow, can lower the bill. Never cut corners on disposal, which is legally controlled.
Sources & further reading
- Property Care Association (PCA) — Invasive Weed Control Group guidance
- Environment Agency — Knotweed code of practice (waste and disposal)
- RICS — Japanese knotweed and residential property, 2022 guidance note
- gov.uk — Japanese knotweed: when you must control it
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.