Should I buy a property with Japanese Knotweed?

I was first asked this question in 2015 from clients of mine who were moving home. The house they wanted to buy had evidence of Japanese Knotweed both inside and outside the boundary. I knew little about it at the time. I have since come across other properties that have had possible evidence of Japanese knotweed. So why do lenders have concerns about it and does Japanese knotweed affect mortgage lending?

Before I talk about mortgage lending let me explain briefly about its history and what the issues are.

Japanese Knotweed was introduced to the UK in the mid-19th century

and was displayed in both botanical gardens and some upper-class society residences as an ornamental plant.

By the end of the century and certainly going into the 20th century it was discouraged from being grown unless properly controlled (not easy to do) given its in unamiable propensity to grow and spread.

The British over the last few hundred years seemed to have an appetite for bring plants and animals from foreign lands to these islands whilst it appears simultaneously doing the same in other countries. Before the British arrived in New Zealand for example they had no grass and no mammals (such as sheep or cows) on the islands. In a pseudo Brit’s abroad kind of a way we wanted a piece of home away. New Zealand as we all know is famous for its butter and lamb.

In Japan there are many species of insects & fungus that help keep its growth under control which we do not have in this country. Other action then has to be taken to control the spread of it.

Japanese knotweed is covered by the Wildlife and Countryside Act 1981 and it is an offence to plant it or cause it to grow in the wild.

Japanese knotweed is classified as an invasive species

and is very resilient. It can cause a lot of damage if not properly controlled. It can grow up to 2 metres in depth and even if herbicide is applied to the growth above the ground the roots can remain alive for many years.

Japanese knotweed can cause damage to brickwork, paving, paths, & drains and therefore needs to be controlled.

If there are possible signs of Japanese knotweed get a specialist survey

If you think there is Japanese knotweed on the plot or near it, or indeed the valuer thinks that may be the case, then you will need to get a survey completed by a professional & qualified firm. They will need to be members of the PCA (Property Care Association).

A survey will provide a formal Japanese knotweed identification showing where the knotweed is located, whether on or near the boundary, the extent of the risk areas and suggest any remedial work or treatment that would need to be done accordingly.

The report will say whether the property, as classified by RICS (Royal Institute of Chartered Surveyors) is Category 1, 2, 3, or 4 if evidence is seen by broadly the following criteria;

Cat 4 – Japanese knotweed is within 7 metres of a habitable space, conservatory and/or garage

Cat 3 - Japanese Knotweed is present within the boundaries of the property, it is more than 7 metres from a habitable space, conservatory, and/or garage

Cat 2 - Japanese Knotweed was not seen within the boundaries of this property, but it was seen on a neighbouring property or land. Here, it was within 7 metres of the boundary

Cat 1 - Japanese Knotweed was not seen on this property, but it can be seen on a neighbouring property or land where it was more than 7 metres away from the boundary

Depending who you use to do the survey some firms offer this for free but may charge a fee of around £170 if there is no evidence of Japanese knotweed.

Japanese Knotweed Management Plan & Guarantee

A Knotweed Management Plan is required for house buying and selling where the subject property has evidence of Japanese knotweed. Most mortgage lenders will insist on proof that there is a management plan in place certainly if there is evidence of it within the boundary and possibly if there is evidence the other side of the boundary. 

The treatment plan can be over a period of typically 5, 7, 10 or 15 years. They tend to come with an insurance backed guarantee. Most mortgage lenders require a minimum 10-year guarantee for the treatment plan to be acceptable. Depending on the amount of work & treatment involved the cost can run into many thousands of pounds.

So how do mortgage lenders view properties with Japanese knotweed?

The lender views with regards to the existence of Japanese knotweed are extremely varied. Some for example will not lend on a property even if its Category 1 i.e. more than 7 metres away from the boundary. On the other extreme some lenders will consider Category 4 i.e. within 7 metres of habitable space as long as a treatment program is in place.

Some lenders will go with whatever the valuer says and again probably suggest a report and treatment plan if Category 3 or 4.

Lenders may also take a view on the application as a whole. If they feel that other aspects of the mortgage application are not strong for example low deposit, credit history and income/employment situation the lender may decline to lend on the basis the Japanese knotweed adds an additional risk which they may not wish to accept.

So should I buy a property with Japanese Knotweed?

If you’ve seen a house or flat that you wish to buy with evidence of Japanese knotweed, as long as a report has been completed and any treatment work is planned or in progress and you’re aware as to how it might affect the ability to get a mortgage then why not. It should not be a major issue. But if there are other issues with the property then it may make you think twice about buying it.

If you have seen somewhere you like that may have evidence of Japanese knotweed and would like to discuss it further get in touch.