19 Aug 2015

Comment: Japanese Knotweed – A Far East plant on home soil

Comment: Japanese Knotweed – A Far East plant on home soil


Iain Considine, Partner, looks at an unforeseen circumstance that could affect home buyers.

Changing jobs or buying a new house are said to be the two most stressful experiences an individual can experience. With most house purchases, the transaction can be seamless, but in some cases there are unforeseeable circumstances which can cause further stress to the experience. Most conveyancer’s will be aware of potential problems which can creep up, and will be well equipped to deal with said problems. Having said that, a problem such as Japanese Knotweed is not an everyday occurrence. 

What is Japanese Knotweed?

As the name suggests, the plant is a weed which grows at an expeditious rate, as much as 1.5 meters per month. The plant originates from the Far East and was introduced by the Victorians for ornamental purposes.

Why is it a problem for residential properties in Scotland?

Despite its exotic origins, the plant is now a serious problem to residential properties in the much cooler climates of Scotland. The plant can cause major structural damage to the external walls of the property, boundary and retaining walls to name a few. In some cases it can mean mortgage lenders refusing to lend. Most lenders will expect the presence of Japanese Knotweed to be noted on the Valuation Report as ‘invasive vegetation’.

Although there is not an overall consensus from all mortgage lenders to refuse lending, the Council of Mortgage Lenders (CML) found a significant reluctance from its members due to the plant’s destructive properties. Individual lenders will consider each case individually, and seek the plant to be treated where possible. However, that does not provide a guaranteed solution to the problem. The lender will look for evidence of the said treatment and also how serious the problem is in the first instance.

Not only does Japanese Knotweed affect lender’s qualification for lending, it can also affect the way in which insurers measure the level of risk involved. Although insurers may not specifically exclude a claim on Japanese Knotweed, most insurers will exhibit reluctance to insure as damage caused by Knotweed is gradual. Therefore leaving the home buyer in a predicament – should they be able to find a suitable lender, they are then faced with finding an insurer who will adequately insure their property.

How can the problem be solved?

Knotweed - although extremely problematic – is solvable. The plant can be excavated from the ground and disposed of at a licensed disposal unit. However this requires extensive excavation and in turn considerable disruption. Dependant on the infestation, a considerably small infestation can cost several thousand pounds to eradicate. An alternative method is Chemical Treatment, however this requires several growing seasons of treatment, usually over a period of three years in order to be effective in eradicating the plant.


Although the presence of Japanese Knotweed is rare, it is a palpable problem for mortgage providers, insurers and home buyers alike. Current owners of properties where Japanese knotweed is an issue should seek to eradicate the plant as soon as possible in order to minimise both the damage and potential delay in the future should they come to sell their property.

Iain Considine, Partner
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