Japanese Knotweed and Mortgages: What UK homeowners need to know

Japanese knotweed isn’t just a garden problem—it can derail mortgage applications and lower property value. Here’s how to manage it properly.

What Is Japanese Knotweed?

Originally introduced to the UK in the 1800s, Japanese knotweed is a fast-growing invasive plant capable of damaging brickwork, foundations, and concrete. Left untreated, it can spread aggressively across property boundaries.

How Is It Treated?

A professional survey should assess the extent of the infestation. Most cases require a herbicidal treatment plan by a PCA (Property Care Association) -qualified company. Severe cases may require excavation. Treatment typically lasts 3–5 years and should include an insurance-backed guarantee (5, 7, or 10 years).

How Does It Affect Mortgages?

Mortgage lenders often hesitate to lend on properties with active or historic knotweed—especially without a clear treatment plan. Lenders want reassurance through professional documentation and guarantees.

What Should You Do?

If you suspect knotweed, seek immediate advice from a specialist mortgage adviser who understands how different lenders treat affected properties. Acting early can prevent delays or rejections.