Once it has established itself, eradicating Japanese knotweed is particularly challenging, and unless you hire contractors experienced in Japanese knotweed removal, it can be an arduous task that can take years to complete and expose you to costly repercussions from the various pieces of Japanese knotweed legislation.
Japanese knotweed causes significant blight to property, which can result in huge diminution in property values (typically of 5% to 20%) if removal works are not supported by appropriate guarantees. As such, you are potentially taking a huge gamble if you don’t get the work done by suitably-qualified experts.
In order to mitigate such risks, you should seek the services of a company specialising in Japanese Knotweed removal to ensure full and guaranteed eradication following an in-depth Japanese knotweed survey to better understand the severity of the infestation. This will ensure you avoid legal action from future occupiers and potentially-affected neighbours.
The cost of treatment plans and pricing for eradication varies depending upon the area of land affected and on the intended use of the land. For the vast majority of cases, a simple herbicide programme will solve the problem. However, if the affected land needs to be excavated in the future (e.g. in order to develop it) then an excavation solution will likely be required.
This could include a range of knotweed treatments from full excavation and disposal of the arisings, to partial excavation and use of appropriate root barrier membranes. A rough outline of costs is provided in the table below.
| Size of infestation | Small (<50m2) | Medium (50m2-100m2) | Large (100m2-500m2) | Very large (500m2-1,000m2) |
|---|---|---|---|---|
| Herbicide treatment | £2,000- £3,000 | £3,000-£5,000 | £4,000-£6,500 | £5,000-£10,000 |
| Reduced dig and root barriers | £2,000-£5000 | £5,000-£10,000 | £15,000-£40,000 | >£40,000 |
| Pick and sort / screening | £2,000-£5,000 | £5,000-£10,000 | £15,000-£40,000 | >£40,000 |
| Onsite relocation and herbicide (treatment bund / lay down area) | £5,000-£10,000 | £8,000-£15,000 | £12,500-£20,000 | £18,000-£30,000 |
| Burial on site | £5,000-£15,000 | £12,500-£20,000 | £18,500-£35,000 | £30,000-£75,000 |
| Full excavation and disposal (dig and dump) | Subject to survey | Subject to survey | Subject to survey | Subject to survey |
If it’s on your land and there’s no evidence that someone else might be to blame for it, then the knotweed problem is yours and it is your responsibility to pay for its removal. If the liability is less clear, then you might be able to share the cost with other parties.
If it is clearly someone else’s fault, then legally you could have a strong case to ask them to pay it.
Herbicide treatment is usually the cheapest option for removing knotweed, but it can take several years to complete and it can limit how you use the treated ground afterwards (e.g. you shouldn’t build on it). In order to obtain the necessary legal protections, you should employ a professional to undertake any knotweed treatments. Of course, doing it yourself is the cheapest option, but the risks of legal action against you could be significant, so it is rarely advised.
If you are worried that you might be affected by Japanese knotweed, then send us a picture. We provide a FREE Japanese knotweed identification service. Simply send us your picture and generally within one business day we will determine whether or not it shows Japanese knotweed. You can also consult our guide to Japanese knotweed lookalikes for the plants that are most often mistaken for knotweed.
