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Japanese Knotweed Removal From Construction Sites

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Japanese Knotweed was brought to the UK in the 19th century. It has since become a significant problem, costing the economy millions every year due to damages and the efforts needed to manage it.

When you’re dealing with construction projects, it’s vital to fully understand the environmental impact and the complex legal issues related to dealing with Japanese Knotweed. Ignoring this aggressive plant can be a huge mistake—it can quickly complicate your projects and trap you in a web of legal problems. As construction activities increase, the challenges associated with Knotweed grow more significant, highlighting the importance of knowing how to handle it properly and eradicate Japanese Knotweed.

We implement a variety of strategies when dealing with Japanese Knotweed on construction sites, from physically excavating the weed to carefully using chemicals.

The Impact of Japanese Knotweed on Construction Sites

Japanese Knotweed, an invasive species from East Asia, has become a big problem on construction sites everywhere. Its growth habit is more than just a nuisance; it disrupts landscaping and can cause significant problems with construction projects. These pesky plants grow fast, breaching foundations, pavements and drainage systems, so professional removal is essential to prevent damage to infrastructure.

Construction companies need to be aware of Japanese Knotweed on development sites. If found, cordoning off the area and getting knotweed material removed is vital. The legal implications of not handling this invasive species correctly are severe. Under the Environmental Protection Act 1990, Japanese Knotweed is classified as controlled waste. It must be removed and disposed of in accordance with the regulations.

Not managing Knotweed can stop construction projects due to the infestation being too big to manage. So, specialist contractors who know the environmental and legal implications of removing Japanese Knotweed are essential to any project.

Environmental Impact

Japanese Knotweed chokes out native vegetation and tips the balance of ecosystems. Its fast spread can make an area uninhabitable for native flora and fauna, resulting in loss of biodiversity. For commercial sites, this means penalties and legal liabilities for environmental damage. It is crucial to stop Japanese knotweed to prevent its spread and mitigate these issues.

By excavating and disposing of Knotweed responsibly, construction companies protect against structural damage and the value and marketability of the site.

Contractors have a duty to remove Japanese Knotweed under the Environmental Protection Act 1990 to ensure the knotweed material, especially the rhizomes, doesn’t spread during excavation. We often use a combination of excavation and root barrier membranes to contain the spread and keep the surrounding soil clean.

Legal Requirements

The Wildlife and Countryside Act 1981 states that moving soil with Japanese Knotweed to non-approved sites is a criminal offence in the UK. Local councils enforce this through planning policies that will affect planning permissions for construction projects and highlight the importance of knotweed control and management. A knotweed management plan is essential to satisfy lenders and mitigate the reduced property valuation risk.

Removing before construction isn’t a legal requirement, but it’s a good idea. Ignoring Japanese Knotweed can lead to land instability due to its rhizome system, which goes up to 3 metres deep and 7 metres wide. Developers need to weigh up the risks and make informed decisions to avoid future problems.

Proper procedures are also crucial. Taking Japanese Knotweed waste to a licensed landfill prevents cross-contamination and meets waste handling regulations. Following these procedures will help construction companies avoid hefty fines for environmental breaches. Our insurance-backed guarantee on the knotweed removal work will give you peace of mind and financial protection against the invasive plant coming back.


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Japanese Knotweed on Construction Sites

Japanese Knotweed isn’t just an invasive plant; it’s a significant problem for construction industries. Being on a construction site can cause massive delays and require monumental remedial work, rendering project timelines and budgets irrelevant. Proper Japanese knotweed removal is critical; otherwise, developers will face significant obstacles in their construction or development projects. Before any excavation work begins, a full site survey must be completed to plan the necessary works.

Construction Site Disruption

Japanese Knotweed has a significant impact on construction projects. Land contaminated with this invasive species is a nightmare for developers and construction companies, often bringing progress to a standstill until the plant is removed. Excavation is the first line of defence, which involves digging out the affected area, the plant, and the contaminated soil. The disposal needs to be done responsibly at a licensed landfill or on-site with soil screening or encapsulation – often referred to as ‘cell burial’.

Time is of the essence in many construction projects. Unforeseen Knotweed finds need rapid responses to keep projects moving. With speed being essential, companies need to rely on professional environmental services to stay compliant and avoid costly delays.

Methods of Japanese Knotweed Removal

When facing the spread of Japanese Knotweed on construction and development sites, it’s crucial to implement effective removal methods. Physical excavation and herbicide treatment stand as the two primary options, each with its unique considerations and techniques. Here’s how our methods can address the infestation challenge:



A tried and tested methodology used on hundreds of sites across the UK.

Using the screening method, the Japanese knotweed rhizome material is separated from the soil material. The Japanese knotweed material is then either transported to licensed landfill at a much lower disposal rate or incinerated on site using a D6 exemption from the Environment Agency or Natural Resources Wales.

The cleaned soils can then be reused in locations away from any construction, normally in soft landscaping areas.

This can reduce the landfill & backfill requirement costs significantly and can also help to reduce the carbon footprint on site due to reduced vehicle movements to landfill.


Knotweed Services can provide a biosecurity operative to supervise any excavations and movement of soils containing Japanese knotweed on site. 

As part of these measures, we can provide a biosecurity boot wash and machine-washing area installed in an area at the entrance to the site.
We will provide all toolbox talks for the main contractor on site, which will be signed by all contractors involved in the operation on site.

We can provide temporary geotextile barriers if required in areas to maintain the biosecurity on site.

Once the works have been completed, we will provide the client with a full biosecurity report.

This method can be used in conjunction with other treatment methods on site.

Commercial Japanese Knotweed Excavation


This treatment method is ideal where time constraints are present and there’s no other option other than to remove both the Japanese Knotweed and contaminated soil to a registered landfill.

By removing all traces of the infestation quickly, this offers a rapid solution to your problem and allows your commercial project to begin groundwork’s almost straight away. When time is of the essence, there is no quicker Japanese Knotweed removal/treatment method.

Any waste taken off-site will be done so with a licensed waste carrier to a suitably authorised landfill site.

Japanese Knotweed Cell Burial


Cell burial comprises of moving Knotweed contaminated soil from one location on site, burying it in an excavated pit which is lined with a root barrier membrane, in a different position on the site.

The burial requirements for Japanese Knotweed are as follows:

  • The Environment Agency recommends that the top of the burial cell should be a minimum of 2 metres below ground level.
  • The overall depth of the burial pit should be in excess of 5 metres deep. All root barrier seams are welded together forming an encapsulated cell from which the Japanese Knotweed cannot escape. Clean soil is then used to backfill on top of the cell.
  • To prevent accidental disturbance of the burial site, it is recorded on all site plans and future land owners should be made aware of the location.


Bunding is the method of relocating contaminated Japanese Knotweed soil to a different area of the site being treated. A bund is a shallow area of the contaminated soil, typically 0.5m deep.

The bund can either be raised, on top of the ground, or placed within an excavation to make the surface flush with the surrounding area.

The purpose of the bund is to move the Japanese Knotweed to an area of the site that is not used. This ‘buys time’ for treatment that would not be possible where the Japanese Knotweed was originally located.


At Knotweed Services we can provide the client with bespoke treatment plans depending on the locations of the Japanese knotweed. 

These plans can work in conjunction with other methods of treatment where access is limited to pedestrian movements i.e., embankments or existing pathways within a site.

This will normally consist of up to 3 visits per annum to apply herbicide by either foliar spray technique or stem injection during the growing season over a period of 3 years, with a monitoring period of 2 years thereafter.

We would select the appropriate herbicides depending on the surrounding foliage or environmental constraints.

After each visit a full treatment record would be provided with photos showing the progress of the works and then an annual report.

Controlled Waste Regulations

When it comes to controlled waste, which includes Japanese Knotweed infested material, construction companies are governed by different laws to private landowners. These laws cover not just removal but also the secure disposal of contaminated waste. Compliance is key and developers must only use registered waste disposal companies for the job to avoid prosecution under UK law.

Off-Site Disposal Requirements

When on-site solutions are not possible due to site constraints, off-site disposal is a necessary but expensive option. Skilled operatives must carefully navigate the rhizome network to limit soil excavation and waste.

A waste carriers license is required when transporting controlled waste like Japanese Knotweed to ensure compliance and prevent accidental spread. Developers and construction companies must comply with the regulations by using correctly registered waste disposal companies, to the letter of the law.

Waste Carriers Licensing

All companies involved in the collection and transportation of Japanese Knotweed material must have a waste carriers license. The Environmental Protection Act 1990 sets out the rules for the disposal of Japanese Knotweed waste, known as “dig and dump”, and it must be carried out under strict regulation and supervision.

Only licensed landfill sites for controlled waste can take knotweed material, so that its handling is not an environmental risk. Expertise and high standards of certification in waste disposal is non negotiable for professionals working in knotweed waste removal from construction and development sites.

Insurance Backed Guarantees

Our insurance backed guarantees are a key part of the process. Our guarantees last up to 10 years and are backed by big insurance companies. For developers and contractors this means an “AA” rated security on the eradication and disposal of the invasive species.

In practical terms our insurance backed guarantees are a pedigree of confidence in the eradication and the compliance with the regulations for controlled waste. It’s proof of the quality and reliability of the work done – an essential requirement when Japanese Knotweed is stopping property sales or finance. For the buyer, seller or developer unsure about the implications of this pesky plant, these guarantees provide a structured, risk mitigated route through the legal and financial jungle.

Best Practices for Prevention and Control

Best practices for prevention and control start with early detection and run all the way through the project. Before you break ground, you need to survey to see if Japanese Knotweed is present. If it is, you need to start eradication before you start construction to stop the plant spreading and causing more damage.

Japanese Knotweed management requires planning. Controlled waste measures must be followed, all knotweed material must be sent to a licensed landfill. Physical excavation is the primary method; but it must be done precisely to avoid leaving behind knotweed rhizome fragments that can regrow. For areas that can’t be excavated, root barrier membranes can be installed to prevent rhizome spread. Clean soil must be used to backfill any contaminated soil.

On-site screening procedures will help you identify knotweed rhizomes from other waste material so you can sort effectively and reduce the risk of spreading the invasive plant. Herbicide treatment can be used as part of a long term management strategy in areas not required for construction immediately.

Construction site management must know the invasive plant species they are dealing with and must use a specialist contractor that knows Japanese Knotweed and its environmental impact. Having an environmental management plan that includes identification, treatment and monitoring of the site is key to stop the plant re-establishing.

Early Detection and Reporting

The fight against Japanese Knotweed on construction sites starts with early detection. Given the species can spread through rhizome growth and can lie dormant for years, proactive measures are needed. Construction staff should be trained to recognize the signs of Japanese Knotweed to report sightings.

When you find it, you must stop any work that could disturb the area, as disturbance encourages the plant to grow. Then you should call Knotweed Services as DIY attempts rarely work and may breach your legal obligations to manage and dispose of the plant responsibly.

Regular site checks by our trained environmental specialists will keep potential infestations under control. we will assess the extent of the knotweed problem and develop a response strategy. The site owner or contractor is responsible for the weed and its spread. Reporting and acting fast is key to Japanese Knotweed management.

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