Devastating Japanese Knotweed and It’s Effect On Buying Your Dream Property

Japanese Knotweed growing through the cracks in concrete

What is Japanese Knotweed?

Japanese Knotweed or Fallopia Japonica was first brought to the UK in the Victorian era by a German-born botanist called Phillip Von Siebold. He found the plant growing on the sides of volcanoes in Japan in the 1840’s, and can also be found in other parts of east Asia. It arrived in the UK in the 1850’s from his nursery in Leiden (Holland) in a shipment of gifted plants, included in this was Japanese Knotweed.

It was originally favoured for its beautiful creamy white flowers, many Victorian people ended up planting Japanese Knotweed in their garden because of this. Later down the line it was used for a variety of uses for example it was cultivated for use as an animal feed, used to stabilise ground round coal mines in Wales and rail companies had the same idea using it to stabilise grass verges next to rail lines.

For example, between 2011-2019 Network Rail had over 6,000 complaints from homeowners whose properties backed on to rail lines and it had encroached or is beginning to encroach onto there properties. There were 37 closed claims that exceeded £500,000! However, the average pay out was around £13,500 for failing to control the proliferation and spread of Japanese Knotweed. Here is an example of a recent case.

Now it is seen as the most invasive species in the UK and on average costs the UK economy £41 Million per year trying to keep it under control. It can diminish a homes value and you could potentially be declined a mortgage if the property is found to have Japanese Knotweed growing nearby or if it’s found on a neighbouring property. So, if you are buying or selling there are somethings you may want to familiarise yourself with.

If you’d like to find out how to identify Japanese Knotweed yourself then you can check out our guide. If you’re still unsure if you may have Japanese Knotweed growing on your property then you can contact us, and one of our team will be happy to help you.

Japanese Knotweed problem in garden in essex

We were sent this photo by A woman who wasn’t aware of Japanese Knotweed, she cut it back completely and this is how it grew in 40 days.

What Problems can Japanese Knotweed cause?

Japanese Knotweed is renowned for its resilience and fast growth, it is extremely difficult to get rid of and will usually require specialist treatment. It also grows rapidly, up to 10cm per day, it has been known to cause damage to properties. For example, there are cases of it managing to grow through the cracks in hard surfaces like concrete, tarmac, or paved surfaces.

For the most part if water can penetrate a hard surface and reach the rhizome system via a crack or if it permeates through the hard material, the plant stems will use the same tiny holes or weak spots in the cracks and will grow straight through it in order to get to sunlight. Once it has broken through to light the stem will begin to grow as normal, expanding and potentially breaking and cracking the object more. This can be extremely damaging if it manages to breach a properties foundation.

The rhizome system tries to search for large sources of water as part of its survival, If the rhizome system is growing near to a drainage system there is a possibility that the root could grow into a tiny crack or a join in the pipe. Again it can grow and expand eventually forcing and breaking apart the pipework and ruining the drainage system.

Japanese Knotweed has also been known to find it’s way into cavity walls. It can find its way into a property through an air brick, a vent, a hole in the masonry or damaged mortar/pointing of the brickwork. If it begins to grow inside the cavity wall it can grow and expand with enough strength to push the walls apart and could result in structural failure.

As mentioned above the damage it can cause along with the issues you can face trying to get rid of this resilient plant are why mortgage lenders are wary of properties with Japanese Knotweed whether it is present on the property or nearby. If you have already bought the house and now found out that you have an infestation of Japanese Knotweed you may struggle to re-mortgage at a later date.

Some mortgage lenders will straight up decline mortgages on properties, others approach the problem on a case-by-case basis and judge applications on the severity of the infestation. These lenders will definitely expect to see a professional extermination programme, with an insurance backed guarantee that lasts several years as it is a possibility that the plant can grow back.

It’s good to stay vigilant and be aware of what Japanese Knotweed looks like and how to identify it, however if you are trying to sell a property with Japanese Knotweed present you must declare this on your TA6 Property Information Form. However, some people may not be aware of what Japanese Knotweed actually is and that is why it’s critical for a surveyor to spot it. When they inspect the property and should highlight the presence of Japanese Knotweed or if the garden is close to an area where the plant is likely to be found.

If it is present and has been declared, then the mortgage lender will still not grant a mortgage unless an extermination plan is in place with an insurance backed guarantee.

The potential effect on mortgages is not the only problem you could face; it has been found that a Japanese Knotweed infestation can knock 10-15% off a properties value. Its estimated that approximately 850,000 – 900,000 UK households are affected and would suffer a depreciation in value, knocking almost £20 billion off property values across the UK.

In a 2019 YouGov poll, the results revealed that half of all buyers would simply walk away from the purchase of the property affected by Japanese Knotweed. It also showed that if they didn’t walk away from the purchase of the property then they would look for a significant price reduction instead. In legal cases, damages are awarded to cover the cost of treatment/removal. It also includes the diminution in value, as well as the potential risk of knotweed re-growing into account.

Japanese Knotweed growing through Tarmac asphalt

An example of how Japanese Knotweed can find and force it’s way through Tarmac or Asphalt.

Why Does It Grow and Spread So Rapidly?

Japanese Knotweed grows rapidly and a lot taller than most plants – up to 3 meters, because of the height it grows to it outcompetes practically all other plants that grow in its vicinity meaning that they end up dying or cannot survive.

Due to its rhizome system (roots system) it can spread quickly as it grows horizontally under the ground and can sprout new stems quickly, without the need for dispersing seeds like most of plants do. This system can grow downwards up to 3 meters into the ground, which if you compared to a plant that grows to a similar height like bamboo, which roots only grow to only a depth of 1 meter!

In its natural habitat Japanese Knotweed’s growth is restricted because of the harsh conditions. As mentioned before it was first discovered on the side of volcanoes, the mountainside climate, regular ash deposits from the volcanoes, pests, disease, animals, fungi along with other competitive plants all contribute to restricting its growth. However outside of this habitat, like in the UK the plant thrives as it has no natural plant competitors, no pests, or animals in the wild that feed on it or diseases that attack it, so the plant literally grows unaffected.

Japanese Knotweed sprouting through the roof of a building

A fresh Japanese Knotweed sprouting through a roof.

How Could JKWClaims.co.uk Help You?

Whether you’re looking to sell your house or you’ve just moved in, getting rid of Japanese Knotweed is crucial and costly. We can obtain maximum compensation for the removal/treatment and any damage made to your property. If you’d like to make a claim or find out more, get in touch.

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