What Is Japanese Knotweed?

Spencer Lion are qualified surveyors in Slough & Windsor, providing structural surveys, building surveys & dealing with party wall matters.

Japanese Knotweed Explained

Japanese Knotweed is becoming an alarming problem. We see sensational cases in the news of destruction to property but what is the nature of this aggressive plant and what is the level of damage that it can cause?

Japanese Knotweed is a bamboo like perennial plant. It is fast growing and strong and can quickly grow to a height of over two metres. Originally it was used by landscapers to provide a fast growing screen. Subsequently, it has been a problem to keep the plant in check and Japanese Knotweed was included in the Wildlife and Countryside Act 1981, making it an offence to plant or otherwise cause Japanese Knotweed to grow in the wild.

Recently a number of lenders have reviewed their policies and subsequently properties affected by the plant have in some cases been refused a loan. There was a general reluctance to lend on properties affected by Japanese Knotweed. Whilst, policies will vary from one lending institution to another some lenders are willing to consider applications for a loan on a case by case basis.

Although conditions will vary lenders will generally want to see evidence of initial treatment and a commitment by the owner of the property to fund a full treatment programme effective against Japanese Knotweed. Although not specifically excluded, buildings insurance policies will not cover damage caused by Japanese Knotweed.

Level of Damage

The damaging effects of this invasive plant are often exaggerated. The most common effects and affected areas are the following:

• Drains & Underground Services – The plant can enter the drainage system and cause blockages and worse case may require relaying the drains.
• Patios & Hard Standing Areas – The plant can grow through cracks or joints in the paved surface causing distortion. The paved areas may require relaying.
• Boundary & Retaining Walls – Garden walls with shallow foundations can easily be undermined by the plant and can exert a lateral force on retaining walls and result in collapse.
• Outbuildings & Conservatories – Generally built with shallow foundations they can easily undermine the sub structure of the building.

Once Japanese Knotweed has been confirmed it must be treated in accordance with a management plan and this will invariably be undertaken by a specialist contractor. Licenced disposal and removal of the plant or contaminated soil must be undertaken in a controlled manner.

Experienced Surveyors In Slough & Windsor

Spencer Lion is one of the leading building surveyors in Slough and Windsor. We have been established for over ten years, with more than 25 years of experience, acting for both residential and commercial clients. To find out more or to arrange a surveyor in Slough please call us on 01753 850304 or email info@surveyorsslough.co.uk