Japanese Knotweed is an invasive plant species that can cause damage to amenity,  properties and infrastructure. This often results in diminution in property values (typically of 10% to 25%) if removal works are not supported by the appropriate guarantees. It can grow rapidly and spread quickly, making it difficult to control. As such, professional management of this plant is essential to prevent further damage and costs. However, the cost of Japanese Knotweed removal can vary depending on several factors. 

The cost of management plans and pricing for control (Herbicide Treatment) or eradication (Excavation, Removal and disposal)l varies depending upon the area of land affected by Japanese Knotweed as well as the intended use of the land. For the vast majority of cases, a simple herbicide management programme will control the problem. However, if the affected land needs to be developed in the future then an excavation solution will likely be required.

This often results in diminution in property values (typically of 10% to 25%)

Typical Herbicide Treatment Costs

Herbicides is either sprayed onto the foliage of the Japanese Knotweed to control and gradually destroy the plant or if a more controlled treatment is required (due to proximity of other desirable plants, habitations, neighbouring gardens etc) herbicide can be injected directly into the stems if they have sufficient diameter.

This form of management is typically long term and applications will need to be repeated several times per season typically up to a period of 3 to 5 years. Off the counter herbicides do not have a strong enough formulation for the general public to effectively treat Japanese Knotweed and can cause deformity induce pesticide resistance and dormanc .

It is therefore important to work with a PCA (Property Care Association) registered professional who will have access to professional grade herbicides that are more effective. Importantly, the technician will have the appropriate training and be able to provide the required documentation to support / guarantee their work.

Prices for a herbicide treatment plan which comes with a 10 year transferable guarantee period can range from £1750 plus VAT for a small infestation (typically less than 25m2) up to £10,000 plus VAT and in rare circumstances even more for a large infestation (up to 1000m2). Ultimately the cost of Japanese knotweed herbicide treatment will be determined by whether you need a knotweed management plan and an insurance-backed guarantee. 

If you there or no long term plans to sell or remortgage your property, then a pay-as-you-go treatment programme may be the answer on a treatment by treatment bsis. In this scenario, a single Japanese knotweed treatment may cost as little as £300+VAT.

Full Mechanical Excavation, Removal and Disposal Costs

This is the most expensive option however it provides instant eradication by mechanically excavating the Japanese knotweed and the soil in which it is growing and taking all the spoil to a licenced landfill site. Following the environment agency guidelines the excavation area can extend up to a depth of 3 metres and extend out to 7 metres from any Japanese knotweed visible above ground.

This option attracts costs from the excavation of large quantities of contaminated soil to be transported in 8 wheel tipper or grab lorries and consigned to landfill for disposal. Licenced landfill sites are required because material containing Japanese knotweed is treated as controlled waste.

The extent of infested soil on site will depend on the lateral and vertical spread of the rhizome system. The maturity of the knotweed and the soil conditions will affect both the lateral and vertical spread, making an accurate assessment of volume difficult.

WAC testing of the soil to ensure there are no elevated contaminants in the soil is also required for this method by the receiving landfill site adding to the cost of remediation.

A professional PCA Japanese Knotweed certified survey (CSJK) can make a big difference as they can ensure that the right amount of waste is designated as knotweed infested. Excavating too much (which would be expensive) and excavating not enough  (which would need to be rectified).

A professional contractor should dig out the visibly impacted area and extend the excavation to around 2 or 3 buffer zone, taking out all material to the full root depth of the Japanese Knotweed. Prices for the excavation and removal of Japanese knotweed are highly variable and depend upon individual site conditions and size of infestation.

For a domestic households, the cost of Japanese knotweed removal typically range from £7500 to £15000+VAT for areas less than 100m2. For larger excavation projects greater than 100m2, the cost will be approximately £12,500 plus VAT for every additional 100m2 area of impacted land. 

Cost Factors

When it comes to Japanese Knotweed removal costs, there are several factors that can affect the price. In this section, we will discuss some of the most significant cost factors to consider.

Location

The location of the Japanese Knotweed can have a significant impact on the cost of removal. If the plant is located in a remote area, the cost of transportation and labour may be higher. Additionally, if the plant is located near a water source, special precautions may need to be taken to prevent the spread of the plant, which can also increase the cost.

Domestic or Commercial

The cost of removing Japanese Knotweed can vary depending on whether the property is domestic or commercial. Commercial properties may require more extensive removal methods, which can increase the overall cost.

Small Area

If the Japanese Knotweed is only present in a small area, the cost of management will be lower. This is because less labour and materials will be required to remove the plant.

Labour Costs

Labour costs are a significant factor in the overall cost of Japanese Knotweed removal. The amount of labour required will depend on the size of the area and the difficulty of access.

Minimum Fee

Many Japanese Knotweed removal companies have a minimum fee for their services. This fee can vary depending on the company and the location of the plant.

Ease of Access

The ease of access to the Japanese Knotweed can also impact the cost of removal. If the plant is located in a difficult-to-reach area, additional equipment and labour may be required, which can increase the overall cost.

Materials

The materials required for Japanese Knotweed removal can also affect the cost. This includes herbicides, excavation equipment, and protective gear for the removal team.

Landfill Charge

If the Japanese Knotweed is being disposed of at a landfill, there may be additional charges for the disposal in the way of landfill fees and government landfill taxes. These charges can vary depending on the location and the amount of waste being disposed.

Insurance Backed Guarantee Costs

When it comes to Japanese Knotweed removal, insurance and guarantees are essential considerations. We understand that homeowners and businesses want peace of mind when it comes to the eradication of this invasive plant, and we offer a range of options to ensure that our clients are fully protected.

One of the main concerns for homeowners is how the presence of Japanese Knotweed can affect their mortgage. Many mortgage lenders are reluctant to lend on properties affected by Japanese Knotweed, which is why we offer an insurance-backed guarantee. This guarantee provides protection against any future regrowth of the plant, giving homeowners the confidence to proceed with their mortgage application.

In addition to the insurance-backed guarantee, we also offer a warranty for our Japanese Knotweed removal services. This warranty provides coverage for up to 10 years, ensuring that our clients are fully protected against any future regrowth of the plant.

We work closely with insurance companies to provide comprehensive coverage for our clients. Our insurance policies cover all aspects of the removal process, including any damage that may occur during the treatment.

At our company, we believe in providing our clients with the highest level of protection and peace of mind. That’s why we offer a range of insurance and guarantee options to ensure that our clients are fully protected against any future regrowth of Japanese Knotweed.

As members of the PCA, JKS are able to offer separately underwritten insurance backed guarantees to sit alongside our 10 year guarantees. This gives our clients additional peace of mind and an increased level of cover should the contractor stop trading. There are two options when taking IBG and which one you require will depend on several factors such as the chosen method option and start date of the insurance.  

The first option is the Knot express policy which provides cover from the completion date of the works subject to a valid completion certificate with cover up to 10 years and is available on herbicide treatment and other mechanical excavation options.

This option has a minimum premium of £56 including insurance premium tax or 0.72% of the contract value on contracts up to £1,000,000 pounds.  

The second option is the Knot new policy which provides instant cover from the contract start date for 10 years and is only available on a herbicide treatment only option. This cost for this option starts at £223.38 including insurance premium tax and increses in line with the amount of scheduled visits and contract value. The cost can be as high as 8% of the contract value on management plans over £7500.

Regrowth and Aftercare Cost

After removing Japanese Knotweed, it is important to monitor the site for regrowth. This invasive plant is notorious for its ability to grow back even after being removed if even a fragment the size of a fingernail is missed. We recommend regular inspections of the site for at least two growing seasons after removal to ensure no regrowth occurs and this would be included in our management plan at no extra cost

If regrowth does occur, it is important to act quickly to prevent it from spreading. This may involve further herbicide treatment or physical removal of the regrowth. It is important to note that regrowth may occur even if the removal process was carried out correctly, as the plant can spread through underground rhizomes.

To prevent regrowth, it is important to implement proper aftercare measures. This may involve the following:

• Regular monitoring of the site for regrowth
• Proper disposal of plant material to prevent spreading
• Installation of root barriers to prevent spread through rhizomes
• Planting of native vegetation to prevent re-infestation

Proper aftercare measures can help ensure that Japanese Knotweed does not regrow and spread, saving you time and money in the long run. We recommend consulting with a professional to determine the best aftercare measures for your specific situation.

About Japanese Knotweed Specialists

Japanese Knotweed Specialists (JKS) is a company who operate nationwide specialising in invasive weed management. Founded in 2006 JKS has successfully eradicated Japanese Knotweed, Giant Hogweed an Himalayan Balsam on many sites across the UK including an 8 kilometre stretch of The River Carron selected on behalf of River Forth Fisheries Trust as well as a 20 kilometre stretch of the River Irvine on behalf of the Ayrshire Rivers Trust in 2014 in order to increase biodiversity & encourage brown trout to spawn in streams previously blocked by invasive weeds.

We have worked on many remediation sites including the new Queensferry Crossing, New Campus College for Sir Robert McAlpine, Twechar Canal Centre for Morgan Sindall & Wokingham Major Highways & Stockingfiled Junction for Balfour Beatty.