Japanese knotweed originated in East Asia and is an invasive plant that can damage property if it's left to grow unchecked. Theoretically, it can find weaknesses between bricks, paving and concrete and eventually cause structural damage if you don't treat it.
The Royal Institution of Chartered Surveyors ('RICS') uses categories to determine the impact of a knotweed infestation, and they updated these in 2022, reflecting more advanced techniques of treating knotweed.
New 'management categories', which range from A-D, replace the old categories, which used to be on a sliding scale of 1-4. The RICS' approach was to give valuers a better way of grading the seriousness of the presence of knotweed, while providing lenders with more clarity than under the old rating system.
Under the previous classification, lenders essentially had to judge risk on the presence of the plant, in some cases, even if it was up to seven metres outside the boundary line. However, as techniques for dealing with knotweed have evolved, reporting on the plant so far outside the boundary line now makes less sense than it did when it was harder to treat.
The new management categories make it easier for lenders to assess the actual damage or potential risk to the property caused by knotweed close to a home, dwelling or structure. Under the new rules, surveyors and valuers will focus on providing an A-D categorisation based on the damage caused or the urgency/difficulty of managing knotweed to bring it under control.
For homeowners and sellers alike, the updates are welcome. While it's rare that knotweed would severely damage a property without being noticed, the mere presence of the plant sometimes used to halt house sales outright. Under the new A-D categories, it is easier to ensure a property is mortgageable if a surveyor reports on knotweed on a neighbouring property, for example, or if it is within the boundary line but far from a home, and will be easy to manage.
If you have knotweed on a property you plan to sell, it still makes sense for a specialist to deal with the problem. This usually falls to you, as the seller, to address, as you will need to report it as part of the property transaction. A proper management plan for dealing with knotweed will need to be put in place by the specialist undertaking the work, which will usually come with a warranty or guarantee. These are important as they will cover you or the prospective homeowners from the maintenance costs if the knotweed reappears.
Knotweed treatment can be expensive because a specialist should handle it, and you will always want to ensure you have a management plan for treatment that you can show during the transaction. While you can, in theory, deal with an knotweed yourself, doing so can cause challenges when it comes to selling your property, as you won't have a warranty or guarantee that will bring buyers comfort or faciliating their financing of the property. By working with a specialist, you are taking the measures necessary to ensure your property is mortgageable.
Usually, you will want to work with a specialist or contractor that belongs to the Invasive Non-Native Specialists Association (INNSA) or Property Care Association (PCA). However, some specialists are affiliated with other official registers that can also carry out the work and provide the warranty and plan you need. Make sure that whoever you hire to undertake the treatment can offer the guarantee you need to show to lenders, which will cover you or a buyer for further treatment if the plant returns within a set period.
Remember that you are usually legally obliged to declare if you have had a knotweed infestation if you want to sell your property. You'll also usuall need to supply your guarantee/warranty and management plan, so working with an expert is generally recommended.
Overall, knotweed may no longer threaten the value of your home in the same was it did in the past, given the advancements in treatment and updated classifications. In some cases, financing can be more of a challenge, although it is much easier today than it was several years ago, and Enness can help you arrange finance in these cases, if management is relatively easily treatable via an expert.
This guide is for information and illustrative purposes only and nothing contain within should be construed as advice or a recommendation. Financing options available to you will depend on your requirements and circumstances at the time. Any changes in your circumstances, any known likely changes, or omissions in the information you provide can affect the suitability of the options available to you. These should be communicated to us as early as possible. If you are considering securing debts against your main home, such as for debt consolidation purposes, please think carefully about this and consider all other options available to you. Your home may be repossessed if you do not keep us repayments on your mortgage or other debts secured on it.
Islay Robinson, a founder of Enness, is widely regarded as one of the UK's leading mortgage brokers. He has been instrumental in delivering some of the most complex and high value mortgages in the UK.