Can You Develop On Land That Has Japanese Knotweed?

Japanese knotweed has been widely publicised in recent years and is now recognised as a huge problem for anyone whose land it decides to grow on.

Despite the increase in awareness, there are still grey areas about land that’s due to be developed: Do landowners need a survey to identify Japanese knotweed? Does a property developer have an obligation to inform future property buyers? Whose responsibility is it to get rid of Japanese knotweed? What are the best methods for commercial treatment?

In this blog, we answer all these questions and shed some light for both those in the construction industry as well as new home buyers

Can You Build on Land That Has Japanese Knotweed?

It may surprise you to learn that building can still go ahead even with a Japanese knotweed infestation present on a site.

If the footprint of the development does not encroach the 7 meter buffer zone for the knotweed infestation, then the knotweed could be treated with a simple herbicide treatment plan supported with a PCA Guarantee. If the knotweed growth and rhizome is within the footprint then mechanical excavation will be required.

To avoid the hefty bills for Japanese knotweed removal, as well as potential legal expenses for not dealing with it, it’s important that landowners get as much information as possible prior to purchase or development.

Issues with Developers and Japanese Knotweed

Typically our experts at Japanese Knotweed Specialists notice the main issue is that knotweed simply isn’t being identified prior to development commencing, and therefore we see so many cases of the knotweed getting spread across a site.

Developers are not legally required to perform a Japanese knotweed survey, but we strongly advise that they do employ a specialist to carry out an invasive weed survey prior to completion. During house exchanges, sellers are required to fill in a TA6 form, where the presence of knotweed would be revealed. For developers, there is no equivalent. It is therefore down to the integrity of the developer and due diligence carried out by the developer.

In theory, some developers could pretend they knew nothing about a Japanese knotweed infestation and still continue with legal building works, not wanting to delay work or take on the expense, but we almost always find that any reputable company simply wouldn’t behave so unethically.

We strongly advise every developer includes a Japanese knotweed survey as a habitual part of their project planning and due diligence. This precaution can save an incredible amount of time and money later on.

Tax Reliefs for Developers with Japanese Knotweed Infestations

Whilst property owners are responsible for the costs of remedy of Japanese knotweed on their property, limited companies that pay corporation tax, can potentially claim removal expenses from a scheme called Land Remediation relief.

This tax relief was introduced in 2009 to alleviate companies who had purchased land with Japanese knotweed. Because knotweed can lay dormant for up to 20 years, a company could even have had a survey where knotweed doesn’t show up, but if it makes an appearance later on, could still claim. Eligible companies must show that they have taken instruction from a Property Care Association member PCA member such as Japanese Knotweed Specialists. The costs of surveys and management may then be covered by the relief scheme.

How To Identify Japanese Knotweed

A professional survey to identify Japanese knotweed will help prevent much wasted time, resource and money. If properly assessed by qualified experts, both developer and purchaser can learn the extent of the problem as well as know what action to take. Like most things, if caught early, Japanese knotweed removal is much easier. This helpful resource will give you a good idea of whether you’re dealing with the invasive weed.

Why Is Japanese Knotweed Such a Problem Anyway?

From railways to derelict buildings, there really isn’t anywhere Japanese knotweed can’t grow. Fast spreading and resilient, Japanese knotweed control is tricky. Japanese knotweed removal is even trickier with lengthy and expensive processes.

Dormant Rhizomes

Rhizomes in the root systems can grow entirely new plants from the tiniest fraction. Dormant knotweed can awaken and begin growing up to twenty years later, from soil disturbance, just as you’d expect from a building development. It’s even been known for Japanese knotweed rhizomes to travel down rivers and end up sprouting miles away.

Building Penetration

A report by the House of Commons Science and Technology Committee observed that Japanese knotweed is capable of growing through new builds. Although this isn’t common, other than for very large, uncontrolled areas of Japanese knotweed, the damage is undeniable.

When compared to other invasive weeds that penetrate buildings, Japanese knotweed was of particular concern because of its rate of growth as well as its strong resistance to treatment and removal.

Worst-case scenarios include the devaluation of property, with some owners taking enormous hits. One couple were dismayed to find that after just a month of living in their new home, the price dropped from £305,000 to £50,000 because of a Japanese knotweed invasion.

Despite the undeniable problems with Japanese knotweed in the UK and Europe, homeowners and developers should not be put off buying a house or property with a history of Japanese knotweed. Provided it has been dealt with by a PCA registered company such as Japanese knotweed specialists, you will have insurance and guarantee that the knotweed is well and truly gone.

The Law on Japanese Knotweed

The law is quite serious about Japanese knotweed, as demonstrated by the growing number of legislations that include mention of it.

It’s best to contact a legal specialist with knowledge of knotweed and development land prior to beginning any work.

Should I Still Buy Land or a Home with a History of Japanese Knotweed

Most developers might understandably be put off building on land with Japanese knotweed present, but technology has moved on and it is very possible to control and eliminate knotweed.

Provided developers have taken steps to use a reputable Japanese knotweed removal company, they not only show integrity, which earns the trust of future home buyers, but they also ensure that they’re not running any risk of spreading knotweed.

What Action Should Be Taken Prior to Building on Land With Knotweed On?

If the plant has already been identified, specific requirements would be needed to get conditional planning permission. Within that should be a clear management plan, with criteria for preventing any further spread as well as total Japanese knotweed eradication.

Depending on the size of the infestation, it may be possible to go ahead with building, by moving the infected area to quarantine. A proper site inspection and Japanese knotweed survey is really a necessity to determine how bad the problem is, because of the weeds root system (rhizomes) ability to grow down as far as 3 meters. Seasons also influence how the knotweed advances, with wintery conditions creating the illusion that the plant is less of a problem than it really is.

Removal of Japanese knotweed waste is considered contaminated, and building contractors are expected to follow even tighter regulations than homeowners.

How to Get Rid of Japanese Knotweed on Development Land

Getting rid of Japanese knotweed depends on the scale and location of the problem. However, most processes follow a similar set of steps.

Be proactive with removal

Deal with any knotweed on site proactively on site, even if the site is not to be developed for many years. Control is better than cure and more cost effective. This will range from:

• Herbicide treatment
• Excavation and removal off site
• Excavation and relocation
• On suite burial
• Screening and incineration

Protect your site with a guarantee

PCA Approved knotweed specialists must have an appropriate warranty or guarantee for any work carried out.

When hiring a specialist ask them if the warranty can be splintered across all development plots rather than having to take out individual warranties. Japanese Knotweed Specialists offer guarantees from five to 35 years, covering sites for the length of a mortgage.

Staff education

Before work is carried out, and building work commences, educating staff on how to spot knotweed while working is key to ensuring you are practicing due diligence while building. The course should also cover how to alert senior managers, and what steps should be taken if it is found.

Part of this should be how to remove waste as the waste from knotweed is considered contaminated and must be removed by an approved expert, or you risk serious fines and further penalties. Japanese Knotweed Specialists offers a Free CPD Training Course that your staff can partake in to learn from our experts.

Japanese Knotweed Specialists have extensive experience with commercial construction sites and are well versed to provide the information and services needed to assure any developer. We also work with Japanese knotweed on council land, utility companies, railway networks and more. Why not reach out to us and see how we can help?

For further guidance from the PCA, see the Guidance Notes for Developers.