Japanese knotweed is a perennial weed that produces tall canes, up to 2.1m (7ft) in height during the summer. It can cause damage through its root system that disrupts building foundations, grows through walls, fences, and flood defences. Knotweed grows up to 10cm a day in summer, causing considerable damage to many properties’ foundations. Its ability to spread rapidly across the country leads to damage to properties due to its extensive underground rhizome roots.
The damage Japanese knotweed causes
Japanese knotweed’s destructive effects can reduce property value by up to 15%. It can grow through paving, tarmac, foundations, flood defences, and building foundations.
Furthermore it can gain access to weak parts of a structure and cause costly repairs, in addition to the cost of removing it.
On the other hand, it is possible that Japanese knotweed may cause no damage to physical property at all, but homeowners will still have to pay to have the plant removed.
How damaging is Japanese knotweed?
Depending on how long it is left untreated and what kind of soil it is built on, a Japanese knotweed infestation can cause varying degrees of harm to a property. The longer an infestation is allowed to thrive, the more powerful the plant becomes. A mature Japanese knotweed infestation can pose a serious hazard to a structure if left untreated.
It is possible for an infestation of Japanese knotweed to amass a large canopy above ground, which can exert pressure on nearby walls and fences.
Long-term damage will be caused by the root structure beneath the ground. These roots grow in size and can conglomerate, causing concrete to distort and drains to become clogged. These roots have the strength to push plasterboard apart and send up shoots that can break through skirting boards in their quest for sunlight.
Effect on property
Japanese knotweed’s predominant effect on a house is financial. The value of the property will become significantly diminished.
Environet conducted an investigation via The Independent, Moneywise Magazine where it was discovered that: ‘approximately 850,000 to 900,000 UK households are suffering an average reduction in value of around 10%, knocking almost £20 billion off property values”.
In many instances, there is a reluctance on buyers to proceed where there is the presence of Japanese Knotweed.