Derby Surveyors

Is it important to obtain a Japanese Knotweed report from a specialist?

This mid terrace house in east London was put on the market at the beginning of the current year, and we were asked to conduct a survey in May. The asking price was £525,000 and the buyer was informed that the property had a history of Japanese Knotweed, but this was treated under a 10-year guarantee. Despite being treated, whilst surveying the property we found that the plant had regrown. The potential buyer withdrew the offer, causing it to be still on the market today and reducing the asking price to £490,000.


How can we treat the spread?

Currently there are two ways to eradicate this invasive plant. Treating the plant with herbicides under a plan is one of the ways but it can take a few years take effect. Removing the plant, roots and affected soil completely is the other option. Although using herbicides is the cheapest, this is only a control measure. The most effective way to eradicate the plant is by removing it. Removing the plant and soil can be expensive, especially if the infected area is of considerable size. However, new methods can reduce the cost by extracting the roots from the soil on site, without the need to replace the soil. Other measures could include installing vertical root barriers to prevent the plant from spreading.

What surveyors must take into consideration while inspecting.

The absence of the plant does not mean it cannot grow again. There are no visible plants in the photos from the sale details of the property when marketed in January. A visual inspection of the property at the time of the survey inspection would not have revealed there were roots hidden in the ground either. This example shows that it is wise for the surveyor to suggest a specialist should investigate whether this plant is present, even if it is not visible. Some specialists are using trained dogs to confirm whether there are any roots hidden in the grounds. 

By Ramon Burgos.

Photo from sales details.

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