At SE Knotweed, knotweed removal cost by method runs from around £1,200 for a herbicide programme to £12,000 for full excavation, with on-site relocation and root barriers in between. The method you choose sets most of the price.
Removal costs from around £1,200 by herbicide to £12,000 by excavation, set mostly by the method you choose.
At SE Knotweed, removal costs from around £1,200 for a herbicide programme to £12,000 for full excavation, with on-site relocation and root barriers in between, so the method you choose sets most of the price.
The figure within each method turns on the size of the stand, machinery access and how much soil is classed as controlled waste. The table sets the four method families against speed, indicative cost and what each suits, and we fix your figure at survey.
| Method | Indicative cost | Speed | Best for |
|---|---|---|---|
| Herbicide programme | £1,200 to £3,500 | 3 to 5 seasons | No sale deadline, soil can stay on site |
| Root-barrier membrane | £2,000 to £6,000 | Days to install | Containing spread near a boundary or structure |
| On-site relocation | £3,000 to £8,000 | Days to weeks | Larger plots with room to bury soil |
| Full excavation | £4,000 to £12,000 | Days | A fast, clear site for a sale or development |
Herbicide treatment costs from around £1,200 to £3,500 across the whole programme, the lowest-cost method, because it leaves the soil in place and needs no machinery or licensed disposal, only repeat visits to inject or spray glyphosate across the growing seasons.
The figure depends on the number of visits, the size of the stand and the monitoring period, usually 3 to 5 seasons. Our herbicide treatment page sets out the visit schedule and what the programme includes.
Full excavation costs from around £4,000 to £12,000, the highest-cost method, because it removes the stand and the surrounding contaminated soil as controlled waste, which means machinery, a registered waste carrier and a gate fee at a licensed facility.
The volume of soil, the depth of the rhizome and site access drive the figure. It is the fastest route to a clear site, so it suits a sale or development that cannot wait. The excavation page explains the process and the waste duty of care.
On-site relocation, or cell burial, costs from around £3,000 to £8,000, because it moves the contaminated soil to a lined cell elsewhere on the same plot and buries it below the depth the rhizome can escape, avoiding the gate fees of off-site disposal.
It needs room on site and machinery, so it suits larger gardens and development plots. The on-site relocation page covers the burial depth, the membrane and the record kept for the property.
A root-barrier membrane costs from around £2,000 to £6,000 depending on the run length and depth, because it installs a certified vertical or horizontal barrier to stop rhizome crossing a boundary or reaching a structure, rather than removing the stand.
It contains rather than clears, so it is often paired with treatment on the affected side. Our root barrier page explains where a barrier is appropriate and where a combination of methods works better.
The best-value method is the cheapest one that meets your timescale: herbicide treatment gives the lowest total cost where you can wait several seasons and the soil can stay, while excavation earns its higher price only when a site must be clear quickly for a sale or build.
Stand size shifts the balance, so a small clump rarely justifies excavation. Our cost by size page shows how the figures change with the stand, and the treatment hub compares the methods in full.
Excavation is the most expensive method because knotweed soil is controlled waste under the Environmental Protection Act 1990, so the cost includes excavation machinery, a registered waste carrier, a waste transfer note and the gate fee a licensed facility charges by the tonne.
Digging deep enough to remove the full rhizome, then importing clean backfill, adds to the total. That chain is why excavation costs several times a herbicide programme that leaves the soil in place.
An insurance-backed guarantee, often a 10 year term, is usually included in the price an accredited contractor quotes rather than charged separately, because the guarantee is underwritten against the treatment method and its monitoring, not sold as an add-on.
It is the document a mortgage lender relies on, so it is worth confirming the term is included when you compare quotes. The guarantee page explains what the cover includes.
You get a fixed price from a survey, because the figure turns on the measured stand, the method and site access rather than a photograph, so a fixed quote follows an inspection and the costed plan we issue with it.
Book a survey and we will confirm the method, the price and the guarantee term, with the survey fee often credited against the treatment. See the cost pillar for how method and size combine.
Tell us the address and what a surveyor flagged. We confirm the plant, record the RICS category and set out the figures.