Japanese Knotweed: What is it and will it affect your mortgage?

Japanese knotweed, the invasive plant that often plagues our gardens, can be a major headache for anyone buying or selling a property, but there is help available if you know where to look. Here we explain what Japanese knotweed is, the impact it could have on your mortgage, and what you can do about it.

Lisa Parker
June 26, 2023

What is Japanese knotweed?

Originally brought to the UK because of its beauty, Japanese knotweed (Fallopia japonica) is a bamboo-like plant with green heart or shield shaped leaves. New leaves start off dark red, but as they mature they turn green. Flowers bloom in late August and September, are cream in colour and cluster together in spikes. Japanese knotweed plants can grow up to 2cm a day, and often reach several metres in height, with roots sometimes stretching 3 metres deep into the ground. Under section 14 of the Wildlife and Countryside Act, it is a criminal offence to plant Japanese knotweed in your garden, or to cause it to grow in the wild.

How can Japanese knotweed affect you getting a mortgage?

Often the mere mention of Japanese knotweed can be enough to make buyers run screaming for the hills, leaving sellers stuck in their current homes. That’s because Japanese knotweed can grow very quickly. The depth of the roots means the plant has the potential to cause major structural damage to properties. It can cause cracks in tarmac and brickwork, and may block drains running under your property. As a result, many lenders are wary about offering mortgages on properties where Japanese knotweed is present or nearby, as they’re worried that any damage caused will make the property hard to re-sell. If you’ve already bought a property and then found Japanese knotweed, even if you’re not planning to move, you could face issues if you want to remortgage

Help is available

Some lenders will decline all mortgage applications for properties where knotweed is present, or even if it is found several gardens away. However, although Japanese knotweed can certainly make it more difficult to get a mortgage, it doesn’t make it impossible. Several mortgage providers look at applications on a case-by-case basis and will decide whether or not to lend based on how close the weed is to the property, and what steps have been taken to eradicate the problem. A lender will require a valuation of the property, and if Knotweed is identified by the surveyor, it will be categorised according to the risk it presents to the property in line with the guidance set out by the Royal Institute of Chartered Surveyors. There are 4 categories, ranging from the presence of knotweed 7 metres from the boundary on a neighbouring property (Category D), through to it already causing damage to the property (Category A). The more severe the category, the more likely there is to be an issue with a mortgage lender. They will often want to see proof that a specialist has assessed and treated the Knotweed, and that their work is covered by an insurance-backed guarantee lasting several years. As different lenders take different approaches to the problem, it’s worth getting help from one of our experts at L&C, as they will be able to let you know which lenders tend to look more favourably on mortgage applications where Japanese knotweed affects the property.

What you can do about it

Don’t ignore Japanese knotweed. Left untreated, growth can be prolific, and what started out as a potentially small problem can quickly become a big one. So, even if you’re not planning on moving or remortgaging for several years, it’s important to take action quickly. Seek advice from a knotweed removal company and get a few quotes before deciding which service to go for. Never try and tackle it yourself, as if you don’t do the job properly it can quickly re-grow.

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