Property valuers have scrapped a rule that determines whether Japanese knotweed is a threat to property.

Earlier this year, The Royal Institution of Chartered Surveyors (RICS) issued new guidance regarding the distance the invasive species is considered a threat to buildings.

Previously, valuers were advised to regard Japanese knotweed as a threat if it was less than 7 metres from a property.

The body now believes that the risk was ‘overstated’ and there is little threat for “robust buildings with substantial foundations, such as dwellings”. Valuers have been under pressure from government because of the ‘chilling’ effect Japanese knotweed has on the sale of a property.

But ATG Group’s Japanese knotweed expert Bernard Mullan says the real issue arises if there are any fractures within the foundations.

“It is understandable why RICS has chosen this course of action. There is a lot of misunderstanding of Japanese knotweed,” he says. “As a result, mortgage lenders can be nervous of the plant, and that can lead to some properties being virtually impossible to sell even if the plant is more than 7 metres away.

“As the latest research shows, a property with solid foundations will not be damaged by the plant. But our concern is that if the foundations of a property are damaged in any way, Japanese knotweed can find even the smallest fracture to grow through.”

When surveying a new development, it is important to check whether Japanese Knotweed is present.