Should you buy a house with Japanese knotweed?
According to recent news, the hot weather has been a positive boon for one common and highly invasive plant in the UK, namely the Japanese knotweed.
The Express has reported over the last few weeks that this perennial is taking over a park in Worcester and locals are worried it’s likely to have a big impact on property values if it manages to spread. Some new home buyers are also finding it a lot more difficult to get a mortgage because of the potential for damage that may be caused in future.
But is Japanese knotweed the property scourge that it’s made out to be? And should you buy a house if you spot this invasive plant in the garden during a viewing?
Why is Japanese knotweed a problem?
Japanese knotweed was introduced to the UK and Europe in the 19th century. Originally considered an ornamental plant, gardeners, homeowners and businesses have been fighting a battle against its invasive growth ever since, particularly in city regions like London and Manchester in England.
Japanese knotweed is a perennial plant that comes back every year and is characterised by heart-shaped or shield-shaped leaves, strong bamboo-like stems and cream-coloured flowers. Left unattended it can grow to heights of 7 feet and take over a garden in next to no time, making it almost impossible for anything else to flourish.
The big problem with Japanese knotweed is not what’s happening above ground, however. It’s what’s developing under the soil. The plant spreads by creating a network of rhizomes beneath your garden and, if these get into the infrastructure of your property, they can cause cracks and other defects to worsen. In extreme circumstances, they could cause major structural damage.
Is the estate agent obliged to tell me there’s a Japanese knotweed problem?
An estate agent has certain legal obligations under the current Consumer Protection Act to let potential home buyers know if there is something wrong with the property that may cause difficulty and add to costs later.
While Japanese knotweed is not mentioned specifically, if you are buying in an area where this plant is prevalent you would expect them to a) have knowledge of what it looks like and b) tell you if it is present in the garden.
If your estate agent is downplaying the seriousness of Japanese knotweed in the garden (or indeed surrounding properties), it’s still important not to take them at their word and carry out a full, professional survey yourself.
Homeowners are legally obliged to be upfront about whether they have Japanese knotweed in the garden – it should be included on the TA6 Part 1 form which details important preliminary information that buyers need to know about a property. Section 7.8 of this specifically asks the question: Is the property affected by Japanese knotweed and the homeowner must answer honestly.
Can I negotiate a lower asking price?
In some cases, you may be able to do so but a lot depends on the extent of the Japanese knotweed and how much it is likely to cost you to either control or eradicate. In certain areas, this may already have been included in the calculation of the asking price. Of course, the price also depends on how many people are interested in the property.
What are the legal implications?
If you have a property where Japanese knotweed is growing, you are not breaking the law. However, if you allow it to get out of control and do nothing about it, not only can you damage your home but it may spread to other properties in the area. When that happens, and it’s deemed to be in part your fault, you could open yourself to legal action.
Can I get a mortgage?
This is a major issue when it comes to Japanese knotweed and it can be a deal breaker. Again, a lot depends on the extent of the infestation and what is being done to address it. Some companies, particularly in areas where the plant is rife, will not offer a mortgage. Others will want a comprehensive plan in place for dealing with the Japanese knotweed before they agree to any loan.
This usually involves putting in place a professional team who will assess the knotweed, how far it has spread and outline a detailed plan for how it should be dealt with. They will also probably insist that this team must be a member of the Property Care Association and have in place a minimum 10-year guarantee backed by insurance.
What about insurance?
Another concern for home buyers is whether the presence of Japanese knotweed will affect their insurance premiums. Unfortunately, if you are already aware that the plant is on your property you will probably not be able to get cover for its removal.
In short, it shouldn’t affect your premiums but it will impact the extent of your coverage which may exclude repairs for any damage caused to the property by Japanese knotweed, including subsidence.
Is it worth buying the property?
The presence of Japanese knotweed can make you think twice about buying a particular property but there are several issues to consider. The first is how much Japanese knotweed is present and whether you can control it or eradicate it from the property. If you are not thinking of selling any time soon and are planning to live in the property for some years, it can be a good option, especially if you get a lower price from the seller.
The average cost of getting rid of Japanese knotweed using a professional team is between £1,500 and £2,000. If you are using an accredited company, however, you also get a 10-year guarantee backed by insurance which should give you complete peace of mind.
It is important, of course, to do your due diligence and check areas like gardens for this invasive plant. You can’t always depend on the seller or the estate agent to be upfront. Make yourself familiar with what it looks like and check your local area for how prevalent Japanese knotweed is and then make your decision accordingly.
You May Also Enjoy
UK house prices growing by 2.5% according to Halifax
UK house prices dip slightly in May, but market remains steady
Estate Agent Content
The cost of voids rises by £200 for England’s landlords
Breaking Property News 5/06/25
