2021 Update

Selling a house with Japanese Knotweed

Joe Bailey

Learn how to identify Japanese Knotweed, whether you can sell your house and what to do remove Japanese Knotweed.

Japanese Knotweed ProblemsJapanese Knotweed Problems

Stress, stress ... stress!

It’s stressful enough selling a property.

If you’re a property developer you’ll take that stress in your stride. If you’re not, and you’re just looking to sell a home, then you will know the stress and strain that the process throws up.

Believe it or not, there are also other aspects of selling property that can be incredibly draining.

If you’re in a position where you’re selling property and you have a Japanese Knotweed problem, you’re quite possibly in for a rough ride. Japanese Knotweed is a big deal and it causes properties to become unmortgageable - meaning house sales to fall through.

We'll take a look at the problem, and see what can be done about it.

So, what is Japanese Knotweed?

Japanese Knotweed roots growing through a brick wall.
Japanese knotweed growing through bricks.
Image source: duntonenvironmental.com

If you have it on your property, you still may not know what it is.

Japanese Knotweed, scientifically known as Fallopia japonica, is basically a highly invasive type of weed that grows thickly and deeply. Like most weeds it is unsightly, but the main reason it causes so many problems in gardens is that it has such a ferocious rate of growth - and the force behind it.

If left unmanaged for even a season, Japanese Knotweed will take over much of a garden space. The main problem is that it can grow through brick too - creating serious structural issues in your building. This is why mortgage lenders will usually refuse to lend on a property with knotweed. And, as we know, if buyers can't get a mortgage, they can't buy.

It is for this reason that so many homes and properties are now proving difficult to sell.

How to spot Japanese Knotweed

Obviously, being a plant, Japanese Knotweed has different looks throughout the year as the growth cycle continues through the seasons.

There are a couple things you can look out for when you are staring at the weeds that are taking over your garden. Of course, they may not be Japanese Knotweed, which is a good thing.

Date of bloom

Around mid-March Knotweed begins to show itself.

Colours, textures and shapes to look out for

Japanese knotweed leaves, and their characteristic "shovel" shape
Notice the distinctive shovel-like lead shape
Image source: bbc.co.uk
  • Its shoots are very distinctive, with red and purple showing through as colours
  • As it passes through the year the stem begins to look like Bamboo and there are large leaves to the plant
  • White flowers are clearly visible before the Autumn
  • Leaves shaped like a shovel

How does Japanese Knotweed spread?

Japanese Knotweed spreads very easily and this is the key problem with the weed.

Fragments and stems of a Knotweed can easily take root if dispersed around a garden. If someone tries to cut the Knotweed or get rid of it in any physical way this can lead to fragments falling to the ground. In soil, the Knotweed will quickly take root. In fact, it really only needs a tiny piece or fragment of the plant to take root and then the cycle of growth will start again.

It can be transported by animals, and can also be transported on a shoe, for example, or an item of clothing. This is important to remember because if you do discover Japanese Knotweed in your garden, don’t attempt to get rid of it. Instead, prevent access to it. This allows efforts to be made to contain and/or eradicate it. 

Essentially, if Japanese Knotweed is found on a property, it should be left alone until a clear plan has been made to eradicate it. The ease of taking root means that first of all it’s best to try and contain it.

What does Japanese Knotweed do?

It’s quite a significant amount of damage. In fact, houses with a Japanese Knotweed infestation could well present as serious problems for years to come.

  • Grows through brick. The biggest issue around Knotweed is its ability to enter cracks and other breaks in surfaces that are usually quite resilient. This is why Japanese Knotweed often gets into pavements and paving stones, as well as the brick work of buildings.
  • Grows through pipes. One key area of damage that a property can see can be found in pipes. We all know that pipes are important around a property, and that they need to be kept clear. If it grows in your waste pipes, for example, you have a situation where a drain run can be obstructed. This can be catastrophic, and can lead to a property owner having to replace a drainage system.
  • Grows through retaining walls. A property that has retaining walls can find that the walls have been infiltrated by Japanese Knotweed. The sheer impact of having a heavy Knotweed growth in a retaining wall can literally mean a wall can suddenly collapse

In the UK, Japanese Knotweed is so invasive that if someone plants it on purpose in the wild they will face a considerable financial penalty of up to £5,000. This shows just how damaging the plant can be! It's extremely durable too. Burning it won't help (as the roots beneath the service will survive), and it can even survive freezing conditions. (It's been found to survive in temperatures of -17 degrees).

If Japanese Knotweed is present your land (or even on your neighbour's land), there is a very good chance it will devalue your property. Surveyors are more aware than ever of Japanese Knotweed and how to spot it, so it's appearing on more survey reports than ever.

How can Japanese Knotweed be dealt with?

There are a number of ways in which Japanese Knotweed can be managed. Each of these has some effect, but in some cases a specialist removal team will need to be involved.

  1. Cutting. The obvious response is to cut the weed. This rids the space of the visual aspect, but as with most weeds this does nothing in the long term. You won't have dealt with the roots by doing this, so the Knotweed will continue to grow and thrive.
  2. Herbicide. This can be used, but has to be managed by a professional contractor. Be ready, also, for the possibility that it can’t be used. This is to do with the location of the property that is to be treated. If it is near wildlife, for example, or a protected scenic area, there is a very good chance that herbicides will not be permitted.
  3. Burning. It has been common practice recently for gardeners to burn waste. This is just like the cutting strategy mentioned earlier in the article. Burning will do a very good job of getting rid of the surface materials, but will make no difference below that surface. So Japanese Knotweed will simply reappear.
  4. Burying Knotweed. This is recognised technique to help get rid of it. Special equipment, such as a root barrier membrane, will have to be used, but as long this is carefully managed you should have the weed buried and not causing harm for some time. This process does take considerable effort to organise, but it is a way of getting rid of the problem.
  5. A Bund. This is basically a "containment area". It can be used in the garden to get rid of the Japanese Knotweed. This process does take a considerable amount of time and organisation is key. However, if it is used, it does mean that you can safely dispose of the weed in a secure part of the garden.

When we've dealt with Japanese Knotweed on our own properties, we've always used the Herbicide route. It is expensive, and takes a long time, but once the treatment plan has begun you'll obtain a Certficate, confirming that a treatment plan is in place. Mortgage lenders will usually accept such a certificate, and it'll make your home mortgageable again. But just beware that it may still be difficult finding a buyer who's happy to purchase a home with Japanese Knotweed - treatment plan or no treatment plan.

It can also take around 2 years of consistent treatment to eradicate the plant completely, and will cost in the region of £2,500-£5,000. An incredible sum of money for a simple weed - but such is the threat level it poses to buildings.

Selling a home with Knotweed

There are numerous examples of people finding it challenging, if not impossible, to sell a home because of Japanese Knotweed.

There are even examples of people not being able to sell a property because the building next door has Knotweed. This has actually happened to us in the past. We had to work with the neighbour to get a treatment plan in place - otherwise neither property could be sold conventionally.

Dealing with costly set backs with neighbours can become a very emotional situation, and the following advice should help you negotiate the problem a lot quicker.

The neighbours

One particularly distressing aspect of Japanese Knotweed is its ability to spread, and people are finding that they cannot sell their property because of Japanese Knotweed being rampant next door. Remember that this weed can infiltrate concrete and you’ll understand why people may not want to move in somewhere that has housed Japanese Knotweed.

Mortgage worries

On top of that, and even more worryingly, people are finding that they cannot remortgage their property or sell it to a mortgage buyer, because Japanese Knotweed is nearby or is onpart of their property. It is a serious issue, and unless a clear solution is presented to a property owner, it can result in the owner being trapped in a property, unable to sell.

The big reason for all of this is the ability for Japanese Knotweed to go deep underground and spread quickly. There have been cases where Knotweed has attacked the foundations of a property, therefore making it difficult for the property to be anything but a liability.

Make a plan

Some lenders have demanded that sellers gain professional support, and have an eradication plan in place so the problem can be solved by experts. Many lenders actually ask that there is a 10-year guarantee from any company that eradicates Knotweed, so that the property is see as being safe and clear.

The long and the short of it is that Japanese Knotweed, even if it is in a field within short walking distance (a few metres) from your home, can be the reason you (or your purchaser) can't get a mortgage.

While this is a major problem for many homeowners, it doesn’t mean that there is no way out. Short of getting rid of the problem yourself, it is common practice for a property owner to pay for a specialist professional to come in and deal with the problem.

Turn to the professionals

Firstly, if you discover that your home has a problem with Knotweed, don't try and deal with it yourself. Even if you get down on your hands and knees and try to cut it or bury it, you may just end up spreading it.

It's a much better idea to hire professionals to do the job.

Cost of Japanese Knotweed removal

Unfortunately, having a professional team in to get rid of the Japanese Knotweed is expensive. An average Japanese Knotweed removal cost, and we’re not considering huge jobs, is around £3,000. This kind of price can be quoted to you even if the problem is next door’s! With this though you'll get a certificate confirming that an eradication plan is in place, and you'll also receive a 10-year guarantee from the company. This is what the lender needs in order to be comfortable lending.

Alternative to removal: Sell up quick and move on

Another option - if you don't want the delays or the up-front cost - is to sell to a company like us. Because we're familiar with all types of issues, we're not put off. In fact, we're happy to buy any house. You can contact us and get a formal offer within as little as 2-3 days, and if you're happy with the price we can complete the purchase in as little as 2-3 weeks.

We'll take care of the knotweed issue, leaving you to get on with your future plans (and leave the Knotweed behind).


Whichever way you choose to deal with Japanese Knotweed, it’s important to bear in mind that lenders aren’t lending against property that has Japanese Knotweed (even if it is a few metres away). UNLESS you have an expensive treatment plan - and a 10-year guarantee - in place. This can be expensive to obtain - and even then buyers may be reluctant to take a property on with Knotweed.

Whatever you do, don't let the problem linger. If left to its own devices, Japanese Knotweed can cause serious damage, and make a house virtually impossible to sell. Act fast, and we recommend contacting the professionals. If you'd like to just sell your home quickly to us and have us deal with it, either click that blue link or hit one of those big blue "Get An Offer" buttons. Then speak with our team, we'll talk you through the process, and we can make you a free, no-obligation offer.


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