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Japanese knotweed arrived in the UK near the beginning of the 19th century, and it is now well established all across the country. A known invasive plant, it is extremely hard and resistant to attempts to destroy it. Capable of growing to heights over 2 meters and, in some cases growing around 10cm per day, it spreads through a complex network of underground fragments. When it takes hold on your land, these underground stems can push up into the foundations of your property, your walls, and your drainage system. The resulting costs can be enormous. 

Obviously, a Japanese knotweed outbreak has implications for the value of your property - and the amount you'll be able to sell for if you want to put your home on the market. In this guide, we'll answer all your major questions about Japanese knotweed, from queries about identifying it to worries about whether it's still possible to proceed with a property sale.

Where Is Japanese Knotweed Found?

You can most often find Japanese knotweed on land and in properties that have been left unattended. Further risk factors include close proximity to canals, streams, or public footpaths, as well as railway lines, motorways, and car parks. Drains, water pipes, and gas pipes can also put you at risk. However, in principle, any property can be affected by Japanese knotweed, so it pays to be vigilant. RICS clarifies in their instructions to professional surveyors that properties are most commonly impacted when there is a garden, and that any weakness in the structure of buildings leaves them vulnerable to a plant infestation. 

How Do I Know If My House Has Japanese Knotweed?

If you're wondering whether your own property has been infested with Japanese knotweed, you simply have to look out for the plant (including in covered areas, sheds, and greenhouses, and places on your land that is harder to access,). Looking at images of the plant, you can learn how to reliably identify it and to gauge just how much it might reduce your property's value. Below, we’ll also provide a detailed description.

However, many other plants look a little like Japanese knotweed, and if you have a busy garden or overgrown land then you can easily become confused about what you're looking at. In cases where you're not sure if you're looking at genuine Japanese Knotweed, consider hiring someone for a professional opinion. RCIS accredited surveyors are specially trained to identify the plant and grade the severity of an infestation, and removal firms often have a similar experience. Once you know what you're dealing with, you can start thinking about how this affects your home's worth and what strategies you can use to overcome the problem.

What Does Japanese Knotweed Look Like?

To identify Japanese knotweed, you should know about the plant's specific lifecycle. In the spring, look out for a crop of red shoots. In the summer, the plant grows most prolifically, producing heart-shaped leaves that become green over time. Summertime can also bring small flowers on a knotweed plant - these are white or cream-coloured. As the plant ages, you can spot shoots similar to bamboo, some of which may have flecks of purple. At this point, the heart-shaped leaves also enlarge, and start to show "veins" tracking along the surface. As you get into autumn, Japanese knotweed will look more yellow or brown, and then eventually reach dormancy in the cold winter months.

It can also be helpful to ask "How fast does Japanese knotweed grow?" - as we mentioned at the outset, it can grow up to 2 metres, so any fast-growing plant that fits the above description should always be viewed with suspicion.

Does Japanese Knotweed Devalue A Property?

As you'll likely expect from how Japanese knotweed embeds itself within a home and its foundations, this invasive plant is capable of doing serious damage to the value of your property. This is why many people consider Japanese knotweed insurance ahead of time. Specifically, you can lose up to 15% of your property's value in the average case, though extreme infestation can entirely devalue your home in very rare cases. You can expect your home to lose value equivalent to the amount you'll need to pay to have the plant eradicated and any damage to the property's foundation repaired. To learn how much your property's value has dropped, then, you need to gauge how much of a hold the Japanese knotweed has on your property.

Do I Need To Report Japanese Knotweed?

If you find Japanese knotweed on your property, you'll probably be worrying about whether you need to tell anyone - and, if so, exactly who you should approach. It is illegal to let the infestation spread beyond the boundaries of your property, but declaring Japanese knotweed is not a legal requirement. So, you can tackle the problem without ever talking to your neighbours or authorities. However, it is a legal responsibility to not let the Japanese knotweed spread further which can lead to unwanted disputes with neighbours, substantial fines, or even imprisonment in some circumstances.

Declaring Japanese Knotweed

The issue of whether you need to tell anyone about Japanese Knotweed gets more complex if you want to sell. In particular, you should declare the infestation to any estate agent you work with so that they can appraise the property's value accurately. Once you reveal the Japanese knotweed problem to an estate agent, they then have to adhere to Consumer Protection Regulations and declare the infestation.  Plus, any arranged sale is likely to fall through if a buyer later discovers that Japanese knotweed was not disclosed. This plant is now a well-known problem for homeowners, so you'll be unlikely to successfully conceal the issue. Buyers also need to know so that you don't misrepresent the property or its surrounding land.

How Long Does It Take To Get Rid Of Japanese Knotweed?

Whether you're keen to sell or just want to preserve your own home, you'll of course be wondering how to get rid of this invasive plant. Unfortunately, in many cases, it takes up to several years to fully eradicate the plant. It is common to think you have done so, only to find yourself dealing with a resurgence.

If you choose to sell your property, it's best to wait until you're sure a treatment plan has succeeded. However, even when you've successfully removed the plant from your property, you still have to mention it on the TA6 Property Information Form that you complete for buyers. This is a permanent requirement, so even if it has been years since you last had a Knotweed outbreak you'll still have to make it known. Indeed, there's now a specific question about Japanese knotweed, where you also have the opportunity to disclose information about your treatment plan. This can help to reassure buyers and allow them to assess risks incurred in taking on the property.

Can I Sell My House With Japanese Knotweed?

As suggested by the answer above, you can sell a property that has suffered a Japanese knotweed infestation. At one stage, banks wouldn't entertain properties affected by Japanese knotweed. This is no longer the case, but such properties are still viewed in a negative light. This means that if you're to sell a property with Japanese knotweed, you have to go above and beyond to get buyers to feel confident about your treatment strategy and to make clear to buyers that you have the situation under control. Otherwise, they may not want to commit to the property, and may also worry about securing a mortgage. 

While the ideal scenario is one where you've fully eradicated the plant, if this isn't an option then you can at least fund an insurance-support treatment program. You can also give buyers information about the distance of the Japanese knotweed, ranging from Category 1 (Knotweed on a neighboring property) to Category 4 (Knotweed within 7 meters of the home and causing active damage to its structure). Different categories will lead to different mortgage deals, but Category 4 cases can lead to limitations on loans to value.  

How Much Does A Japanese Knotweed Survey Cost?

If you arrange a Japanese knotweed survey with RICS, it will cost anywhere between £135 and £250. The price will be determined by the specific company commissioned by RICS. You may be able to obtain an informal survey free of charge just to find out if you actually have the plant on your property, before paying for an in-depth purchase if tests for the plant are positive.

What Does A Survey Include?

Japanese knotweed surveys should always be conducted by surveyors with full PCA accreditation who hold certificates in Japanese knotweed assessment. The resulting report should include the following:

  • Proof of the surveyor's qualifications regarding the knotweed
  • Information about whether Knotweed is present
  • Details about the severity of any infestation
  • Whether there are any roots or fragments underground
  • Whether there is visible vegetation above ground
  • Photographs to support claims made in the report
  • A clear map detailing where the property is being damaged by the plant
  • The overall condition of your land
  • The purpose of your land
  • The specific RICS Risk Category (1-4) that applies to your property
  • Whether any buildings are affected
  • A summary of the best treatment for your situation
  • A cost assessment for the treatment plan
  • Any suggested precautions to reduce or prevent spread.

Problems Faced When Selling A Property With Japanese Knotweed

Japanese knotweed can cause significant stress, especially if you want to sell your property. The two major issues you might face are structural damage, limited mortgage lenders and competition from knotweed-free properties.

Structural Damage - If the Japanese knotweed infestation has damaged your land, it will put off prospective buyers. However, if the knotweed has started to affect the home itself, including the walls and foundations, it may seem like too much of a headache to most people on the housing market, and they'll simply choose to go elsewhere. You can of course commit to eradicating the knotweed and repairing the home's structure before a sale, but this means you'll also lose a lump sum of cash and need to wait longer than you'd like to put the property on the market. This is not really a viable option if you need to sell your house to downsize, are going through a relationship separation, or have to relocate for a new job opportunity.

Limited Mortgage Lenders - As noted above, even though it's now possible to get a mortgage for a property with Japanese knotweed problems, there is still a serious stigma attached to such mortgage requests. Where a Japanese knotweed mortgage is granted, the mortgage may be prohibitively limited. This means that often, a cash buyer will provide you with the best opportunity for shifting a property with knotweed problems. Cash buyers like Property Buyer can take on homes in any condition, meaning you can make a quick sale with little effort. You won't have to pay for repairs or treatment plans, and nor will you have to wait out the treatment process or go through the long-winded process of providing reassurance to prospective buyers. 

Buyers Prefer Knotweed-Free Properties - At the end of the day, there's just no denying that prospective buyers prefer a knotweed-free property. Whatever their reason for buying a home, no one dreams of acquiring land that is rife with a hardy invasive plant species. Consequently, even if you do everything advised above (such as comprehensive surveys and visible treatment plans), you may still just be unable to shift your property on the traditional market. Meanwhile, in auctions, you're also legally required to disclose the knotweed history and therefore will make much less money on the property - if you manage to sell it at all. To get buyers to see the value in the property, you'll need to lower your reserve price substantially.

Has Your Property Got Knotweed? We Can Still Buy It

It's natural to feel frustration and despair when dealing with Japanese knotweed. However, the good news is that cash buyers will buy knotweed properties - even if they're significantly damaged. At Property Buyer, we understand that you may not have the time to invest in the years it often takes to get a property up to the standard required for a good sale, and we're happy to take it off your hands. 

No matter your reason for requiring a fast cash sale, you can speak to us in confidence and we'll quickly arrange an estimated valuation reflecting what we can pay for your home (based on nearby properties and on the severity of your knotweed problem). Next, we'll draw up a provisional agreement, and then subsequently conduct a full, in-person valuation. What's more, we can do all this and transfer the sale price to you within just a couple of weeks - maybe even less if it's especially urgent for you. Whether you tackle the knotweed yourself or sell to us, you won't get the price you'd get for a knotweed-free property. However, we commit to offering you the highest reasonable price given your circumstances, and once you sell to us you may never have to think about Japanese knotweed again.

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