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Top Tips – Japanese Knotweed And Its Effect On Property Value and Mortgages

Japanese Knotweed growing through concrete asphalt

What is Japanese Knotweed?

Japanese Knotweed or Fallopia Japonica was brought from Japan to the UK and Europe in the 1850’s by German botanist Phillip Franz von Siebold. It was initially loved for its beauty, with its interesting heart or shovel shaped leaves and bright red spotted bamboo like stalks and pretty white creamy flowers that bloomed in late summer.

By 1854 it was available commercially in the UK, where it was grown in people’s gardens, eventually it started to be used for cattle feed and used in Welsh mining towns to stabilise ground to prevent landslides. Rail companies also used it to stabilise land by railway lines to strengthen verges it is then believed to of been spread more when constructing homes and roads.

In Japan it is found on the side of volcanoes and due to the different climate as well as ash from the volcanoes it grows very little, and the plants stay relatively small. However, in the UK with a different climate and no volcanoes it grows rapidly, up to 20 cm every day in some cases. Due to how tall and quick Japanese Knotweed grows it suffocates all other plant life around it. The large leaves stop all other surrounding plants from getting sunlight and its large root system know as rhizomes allow it to obtain the majority of the nutrients from the ground, giving other plants growing near it no chance of survival.

Wondering how to identify Japanese Knotweed, we have a blog post on the key features to look out for!

Japanese Knotweed Infestation on a property
A Japanese Knotweed infestation on a property.

Why Does Japanese Knotweed Cause Such A Problem for Homes and Homeowners?

Japanese Knotweed has been known to cause structural damage to homes across the country. It causes damage to houses as it can forcefully grows through cavities and cracks in brickwork, asphalt, concrete, walls and also gaps in pavements. Due to this it can damage and uplift structures such as pavements, it can also damage drainage systems. This causes Japanese Knotweed to devalue homes by up to 10-15%, depending on how close it is to your home.

Japanese knotweed is estimated to affect up to 1.45 million homes throughout the UK, which is said to be around 5% of residential properties. It is becoming quite the occurrence of being presented with a home that has either been troubled with Japanese Knotweed before or currently has a problem with it, this is why it’s best to be vigilant and educate yourself about this invasive species as there are cases of surveyors missing it when surveying properties so, it’s worth understanding how Japanese knotweed affects homeownership and a property’s value.

How Does Japanese Knotweed Affect House Buying?

If you are looking to buy a home and Japanese Knotweed is present, then it is highly likely that mortgage lenders will be reluctant to offer you a mortgage. Unless a full specialist insurance backed treatment plan for the removal has been put into place to ensure the problem is being dealt with.

Allowing the buyer to be covered for a number of years in case the problem comes back, due to how hard it is to get rid of, it also covers the seller of the home meaning they won’t be held responsible, and no legal action can be taken against them. Dependant on the severity of the problem it can cost up to £15,000 to rid a garden of Japanese Knotweed.

The Royal Institution of Chartered Surveyors (RICS) has four categories that break down the severity they believe Japanese Knotweed could cause to a property, this official guidance is the primary source that mortgage lenders, building societies and banks use to view your knotweed problem, however these are just a guide – and each mortgage lender is different.

These categories are:

Category 1

Knotweed is found in a neighbouring property, more than seven metres, or an empty space like a railway bank or wasteland.

Category 2

Knotweed is within seven metres of your property but not within it.

Category 3

It is within the boundaries of the property but is within seven metres from a living space. You will need a professional opinion.

Category 4

The worst. It is within seven metres of the property and causing damage to walls, paths or foundations. This needs immediate professional intervention.

More detail can be found on page 16 of this document here.

Japanese Knotweed Growing through and out of a wall
Knotweeds effect on brickwork.

How Does Japanese Knotweed Affect House Selling?

Due to the severity of the problem any UK property seller will be asked to disclose if they have a Japanese Knotweed infestation on or near the property in a TA6 property information form. If a seller does not declare Knotweed to be present on the property and it’s later found there with the possibility of it being damaging to the property; then the TA6 form offers some security. It can potentially be taken through a legal case for misrepresentation of a sale, so this can give some assurance to a potential buyer. In terms of new build homes they are also include a homebuyer report to flag any issues that require urgent action, Japanese Knotweed being one of them.

Japanese Knotweed Penetrates concrete
Penetrates Concrete with ease.

Why do Mortgage Lenders have a Problem With It?

Japanese knotweed is renowned for being able to find its way through cracks even in materials most plants could never grow through, they can break open cracks in foundations, brick walls, and damage sewage and drainage works. Which can all be very costly to fix or repair, even if this is done the plant is not dead so can grow back very quickly and do the same. Even when it appears to be killed off, it often lies dormant underground, when split open again it grows back like before.

Mortgage lender see this as a big problem, for example if you wanted to build an extension, conservatory or lay a patio, and you were to dig through the original rhizome system it can reawaken the plant. So many mortgage lenders believe it affects not just the existing structure but puts any future structures at risk also. This is why they can be reluctant to lend on a property with it. This is why insurance backed treatment plans are needed to move forward.

Japanese knotweed infestation right outside a home
A bad infestation on someone’s doorstep.

Can JKWClaims 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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