How Much Does It Cost to Remove Japanese Knotweeds?

Due to its bad reputation, mortgage companies often refuse to lend if Japanese knotweed is an issue on site unless an insurance backed guarantee and management plan has been established. However, there is evidence that Japanese knotweed is not as big an issue as once thought. That said it is still a problem that should be dealt with by professionals.

What is the price tag of Japanese Knotweed removal? The average cost of removing a knotweed infestation for a domestic area would be about £500 to £2000 for an area 20m2 or less, £2000 to £3000 for a 20-50m2 area, or £3000 to £5000 for an area 50m2 to 100m2.

As for a commercial site area, a herbicide treatment over five years may cost £1000 to £3000 for an area of up to 50m2, £3000 to £5000 for a 50-100m2 area, £4500 to £6500 for a 100m-500m2, or £5000 to £10,000 in the case of a 500-1000m2.

When it comes to the approach of reducing dig & root barriers with herbicide treatments, it will cost roughly £2000 to £5000 for an area 50m2 or less, £5000 to £10,000 for a 50-100m2 area, £15,000 to £40,000 for a 100m-500m2, or £40,000+ for a 500-1000m2 area.

For onsite relocation and herbicide, expect to pay £5000 to £10,000 for a 50m2 or less, £11,000 to £20,000 for a 50-100m2 area, £12,500 to £20,000 for an area of 100m-500m2, or £18,000 to £30,000 for a 500-1000m2 area.




For a full excavation and disposal, also known as a dig and dump, costs land around £5000 to £20,000 for up to a 50m2 space, £14,000 to £39,000 for a 50-100m2, £35,000 to £120,000 for a 100m-500m2, and you need a budget of anywhere from £100,000 to £200,000 should it be a 500-1000m2 area.

The total costs of Japanese knotweed removal can also be influenced by the type of treatment, the nature of the treatment area, ease of access, number of tradespeople hired, the materials used for the treatment, and the location of your property.

If you live in the southeast (London especially), you can expect to pay higher Japanese knotweed removal prices than if you were based in the north of England, Scotland, or Northern Ireland. This is due to the varying costs of living throughout the UK, leading tradespeople to set rates appropriate to their region.

Domestic Area of Knotweed Infestation

Size of Area Cost
20m2 or less £500 to £2000
20-50m2 £2000 to £3000
50-100m2 £3000 to £5000

Commercial Site Area of Knotweed Infestation

Removal Type 50m2 or less 50-100m2 100-500m2 500-1000m2
Herbicide treatment Over Five Years £1000 to £3000 £3000 to £5000 £4000 to £6500 £5000 to £10,000
Reduce Dig & Root Barriers with Herbicide Treatments £2000 to £5000 £5000 to £10,000 £15,000 to £40,000 £40,000+
Pick and Sort/Screening £2000 to £5000 £5000 to £10,000 £15,000 to £40,000 £40,000+
Onsite Relocation and Herbicide £5000 to £10,000 £11,000 to £20,000 £12,500 to £20,000 £18,000 to £30,000
Burial on Site £5000 to £15,000 £10,000 to £20,000 £18,500 to £35,000 £30,000 to £75,000
Full Excavation and Disposal (Dig and Dump) £5000 to £20,000 £14,000 to £39,000 £35,000 to £120,000 £100,000 to £200,000

What are the Supply Costs of a Japanese Knotweed Removal?

The supply costs of removing Japanese Knotweed will make up the majority of the overall cost. This section will break down how much the supply costs would be for different types of treatments/approaches.

Supply Japanese Knotweed Removal Cost

Removal Type 50m2 or less 50-100m2 100-500m2 500-1000m2
Herbicide treatment Over Five Years £910 to £2750 £2820 to £4550 £3730 to £5800 £4640 to £9100
Reduce Dig & Root Barriers with Herbicide Treatments £1910 to £4750 £4820 to £9550 £14,730 to £39,300 £39,100+
Pick and Sort/Screening £1910 to £4750 £4820 to £9550 £14,730 to £39,300 £39,100+
Onsite Relocation and Herbicide £4910 to £9750 £10,820 to £19,550 £11,140 to £19,300 £17,640 to £29,100
Burial on Site £4910 to £14,300 £9820 to £19,550 £18,230 to £34,300 £29,640 to £74,100
Full Excavation and Disposal (Dig and Dump) £4100 to £19,750 £13,820 to £38,550 £34,730 to £119,300 £99,640 to £199,100

What are the Additional Costs of Removing Japanese Knotweed?

There are various added costs that may apply to the removal of Japanese knotweed. Let's take a closer look at some examples.

Minimum Fee

In many cases, tradespeople will charge a minimum fee, either as a cost added to your overall bill or one that is incorporated into your bill. For instance, if you face a daily labour charge, then whether the work lasts four hours or seven hours, you'd pay for one day of labour.

Treatment Area/Type

The type of treatment used will impact on the cost of the work as will the treatment area. For instance, herbicide is a cheaper option than more disruptive options such as full excavation and disposal. The easier a treatment area is to work with, the shorter the work will be, and the less it should cost overall.

Number of Weeds

With more weeds, the more extensive the work will be to remove the Japanese knotweeds successfully. As a result, the job will take longer, and you can expect a higher cost overall.




Size of Area

As shown in the opening section, the larger the area, the more Japanese knotweed removal will cost. For a small 50m2 area, the removal may cost 10% or less than removing Japanese knotweed from a much larger 100m2 area.

Materials

The materials used in treating Japanese knotweed will also shape your final bill. That is not just the type but the quality of the materials too.

Number of Tradespeople

In most cases, one specialist is hired to deal with Japanese knotweed removal. However, for larger projects, two or several tradespeople will be needed. The more people hired, the higher your labour expenses will be.

Of course, with more people on the job, the quicker it will take. For this reason, whether the number of tradespeople will impact the cost overall by increasing it or decreasing it will depend on how well the tradespeople work together.

Duration

The longer the work takes, the more the labour cost will be. Considering that the supply costs are the most significant factor in the price in most cases, the duration is still not a massive cost factor.

Tradesmen Costs for Japanese Knotweed Removal

In this section, we'll break down the labour costs of removing Japanese knotweed. We will also consider how these costs may vary across the UK. The average labour cost of removing Japanese knotweed is £20 to £50 per hour.

Given the timescales involved, the labour cost of Japanese knotweed removal on a domestic property would be approximately £180 to £450.




The cost for a small area, whether domestic or industrial of 50m2 or less would cost about £90 to £250, with the labour price reaching £180 to £450 for a 50-100m2 area, or £270 to £700 for a 100-500m2, and the price is £360 to £900 for a 500-1000m2 space.

How Long Does It Take to Remove Japanese Knotweed?

We'll now consider the durations involved in removing Japanese knotweed. We'll look at how long it generally takes based on the size of the area and considering what factors can impact the duration.




For an area of 50m2 or less, it would take about half a day. In the case of an area that is 50-100m2, expect it to last a day. For a 100-500m2 area, expect it to take about a day and a half, but for a 500-1000m2 space, it will take two days or more.

The time-affecting factors include the number of tradespeople, ease of access, the type of treatment used, and the size/type of the treatment area.

Types of Japanese Knotweed Treatments

For this section, we'll take a closer look at the various forms of Japanese knotweed treatment. We will consider the pros & cons of each option.

There are various ways of spotting Japanese knotweed. Firstly tell-tale red shoots will appear. Their leaves have a shovel-like shape, the Japanese knotweed flowers have a creamy white colour, and the leaves will begin to yellow with time. More information can be found using the RHS website.

Herbicide Treatments

This approach involves the use of herbicide, a substance that is toxic to plants and may be used to remove Japanese knotweed. It is also one of the cheapest options available when it comes to removing Japanese knotweed.

However, the downside to herbicide is that it is not an environmentally friendly option, and it can be harmful to human/animal's health.

Pros:

  • Generally effective
  • Cheapest option

Cons:

  • Not eco-friendly
  • Can be harmful to health

Excavation Treatment

The process of excavating involves simply removing all viable plant material. It is essentially an attempt to completely uproot the knotweed and ensure that it can't grow back. After all, if the herbicide is only used on the surface, there is no guarantee that it will work.

Excavation is a more expensive, disruptive, and time-consuming approach, however. In many cases, seven metres of excavation horizontally in every direction from the infestation perimeter may be needed as well as excavation to a depth of about three metres.

Pros:

  • Virtually certain to work if done right

Cons:

  • More expensive than using a herbicide
  • Disruptive

Sifting & Screening

This involved screening infested soils and removing all viable plant material such as other visible contaminants. Excavation can also be conducted using an appropriate excavator. This is a fairly thorough approach and is generally expensive.




Pros:

  • Usually very effective

Cons:

  • Costly option
  • Time-consuming

FAQs

Q: What does Japanese Knotweed look like?

A: For Japanese knotweed identification, it consists of creamy-white tassels that reach up to six inches in height, tall canes with a resemblance to bamboo, and leaves with a shovel or heart shape.

It's important to distinguish it from plants that look like Japanese knotweed such as lesser knotweed, ornamental bistorts, and bindweed.

Q: Which is the best treatment for Japanese knotweed removal?

A: Herbicide is the best option in most cases, but it depends on your preferences. Excavation can be more eco-friendly and all but guaranteed to permanently remove the source of the issue while using a herbicide may not.

Q: What are the consequences of not removing Japanese knotweed?

A: For one, it can lead to structural problems with buildings, and it may cause issues with getting a mortgage.

Beyond that, if you knowingly let contaminated plant material or soil spread into local wildlife, you could face a fine of as much as £5000 or face up to two years in prison.

Q: Can I remove Japanese knotweed DIY?

A: You should hire a specialist to deal with the removal of Japanese knotweed. If not, you should at least seek professionals' advice and only undertake this work, so long as you have obtained the necessary planning permission/building regulations approvals.

It's also vital that you are confident you know exactly what is involved. If you have any doubts or/and would like to know more about any official approvals needed, please contact your local council.

Q: Is Japanese knotweed dangerous to touch?

A: It is not harmful to touch for people, but the risk is that you could cause it to spread more simply by tugging at it.

Sources

  1. https://www.knotweedservices.co.uk/japanese-knotweed-removal-costs/
  2. https://www.phlorum.com/services/japanese-knotweed/japanese-knotweed-removal-cost/
Author: Dean M

I have a Bachelor's Degree in Creative Digital Media, I'm a freelance writer and I've worked for clients such as the British Blockchain Association and I have experience in writing articles, YouTube video scripts, online guides and newsletters. I have written and produced many short films as well as a web series and feature film. I am also currently working on a novel.