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Japanese Knotweed Removal Cost & Prices 2023

Japanese Knotweed can break foundations, penetrate concrete, tarmac and other super-tough materials. Once established on a piece of land, it can cause serious issues and one thing is for sure – it will not go away on its own. 

There is a great deal of misinformation and confusion surrounding Japanese Knotweed. If you find it on your property, then it doesn’t mean that your house will have to be knocked down.

However, there are serious implications to not tackling a knotweed problem, both for builders – commercial and self-build, and homeowners. 

In this article we’ll cover how much you can expect to pay to remove Japanese Knotweed and other common questions around Japanese Knotweed.

Average Removal Cost

Other than the method of Knotweed removal in question, the primary factor in costing Knotweed removal is the size of the area. Japanese Knotweed spreads quickly but if you catch it quickly enough, it can be confined to small spaces.

By compiling quotes from 5 specialist knotweed removers and 7 secondary sources, we discovered these average costs for Japanese Knotweed removal in the UK. 

Type of Removal20m² - 40m² area40m² - 60m² area60m² - 80m² area80m² - 100m² area
Herbicide Treatment£500 to £850 over 5 years£700 to £950 over 5 years£1,000 to £1,400 over 5 years£1,500 to £2,500 over 5 years£2,200 to £5,000 over 5 years
Sifting and Screening £1,000 to £1,500£1,500 to £2,250£2,250 to £3,250£3,250 to £4,250£4,250 to £5,500
Excavation and Root Barriers£1,000 to £1,600£1,500 to £2,350£2,250 to £3,350£3,250 to £4,550£4,250 to £5,800
Complete Excavation with On-Site Disposal£2,000 to £4,000£4,000 to £6,000£6,000 to £8,500£8,500 to £11,500£11,500 to £16,000
Complete Excavation with Off-Site Disposal£3,500 to £8,000£5,500 to £11,000£8,000 to £14,000£12,000 to £18,000£15,000 to £30,000+

Available Methods of Removing Japanese Knotweed

There are several methods for removing Japanese Knotweed. These range from more basic herbicide treatments to manage the problem to full excavations. 

Here is a breakdown of the most common Japanese Knotweed removal methods:

Herbicide Treatment – Cheapest – £1000 to £2500 for a typically-sized infested garden

Japanese Knotweed cannot be killed using standard garden weedkillers. Herbicide needs to be administered at regular intervals where a trained specialist will spray and inject the Knotweed. This eventually tires and kills the plant. 

However, this is considered more of a management solution rather than a complete removal solution – the Knotweed will likely return. Costs for herbicide treatment cover a 5-year period on average. 

Sifting and Screening – Lower Middle – £3000 to £5000 for a typically-sized infested garden

Sifting and screening involves digging up the suspected area, sifting the soil and screening for Japanese Knotweed material. Rhizomes will be selected and removed, allowing the remainder of the soil to be replaced at the site. 

The contaminated soil and material will be burned or removed from the site. Since some rhizomes are likely to remain in the ground, this isn’t always completely effective, but should seriously stunt the growth of Knotweed or kill it off altogether. 

Excavation and Root Barriers – Upper Middle – £3000 to £6000 for a typically-sized infested garden

Sifting and screening can be combined with a wider excavation of the contaminated soil, including the emplacement of root barriers that stunt the spread of Knotweed. This is a near-permanent solution if the excavation is effective at removing the rhizome.

Full Excavation with On-Site or Off-Site Burial/Disposal or ‘Dig and Dump’ – Most Expensive – £8000 to £1200 for a typically-sized infested garden

A full excavation will remove the entire contaminated area and either bury the soil on-site at a depth of over 5 metres, or off-site. The material may also be incinerated. This is the most comprehensive but expensive option, it should totally remove all contaminated soil from the land. Knotweed must be disposed of to strict protocol to avoid breaking the law – you can’t just dump it in any old place. 

The best option for Knotweed removal depends on the following factors: 

  • Access to the site 
  • Geographical location
  • Ground/soil type and conditions
  • Knotweed maturity
  • Rhizome depth and lateral spread
  • Site characteristics

If you’re unsure of what type of removal and disposal you need, consult with a surveyor who can conduct an in-depth knotweed survey. Independent surveyors can provide professional advice that can be forwarded to the knotweed removals firm. 

One key point is that any removal technique can be backed by an insurance-backed guarantee (IBG). This guarantees that the Japanese Knotweed will not return for a set period, usually between 2 and 10 years. An IBG-backed removal is usually required for mortgage lenders. 

Get Pricing on Japanese Knotweed Near You

We’ve done our best to give you a good idea of what you can expect to pay to remove Japanese Knotweed.

However, our guides are not a substitute for a fixed quote specifically for you.

We work with all the best Japanese Knotweed removal companies ready to price your job. Get free, no-obligation quotes in your local area and compare prices using the form below.

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About the Author

Alex Johnson is a qualified quantity surveyor and writer with a passion for conducting original research and uncovering the true cost of jobs. His cost data has been referenced by EDF Energy and the Scottish Government.