Fast growing knotweed roots can exploit existing crevices, gaps or joints in home foundations, drainage pipes and other man-made structures. Over time, cracked asphalt, concrete or aging brickwork can become compromised, paving the way for lawsuits and costly repairs.

Recent litigation
It has only been in recent years that knotweed-related litigation has appeared in the United States; case law is more established in Great Britain.

In 2023, a Massachusetts couple who had recently purchased a home in a new development were awarded $186,000 in damages incurred after the developer, who was told by a contractor that knotweed existed on the property, directed the contractor to grade the lot using knotweed-contaminated soil mixed with clean loam. 

In a 2017 case in Westchester County, homeowners successfully sued a neighboring shopping center, claiming the defendant was negligent in allowing a "private nuisance" to spread onto their property. The homeowners were awarded $535,000. More details about the case can be found here on page 23.

Impact on property values for sellers
Knotweed is also capable of reducing home value for those wishing to sell their home. According to one UK company specializing in knotweed removal,  the mere presence of knotweed typically devalues property by 5-15% and in extreme cases, up to 20%. Such devaluation is caused by the cost of professional treatment and removal. Failure to inform potential buyers of a knotweed problem can result in litigation.

Mortgage complications
UK homeowners are legally responsible if knotweed on their property spreads to adjoining neighbors' property. And mortgage lenders there may be loathe to offer loans for properties containing knotweed, even requiring documentation of a professional remediation plan if knotweed is present within seven meters (about 7 yards) of the property in question. Indemnity insurance may also be required.