Japanese Knotweed and Mortgages: What Lenders Require

Japanese knotweed is one of the few plant problems that can directly affect whether a property can be mortgaged. It is not the plant alone that causes the difficulty — it is what lenders and surveyors do when they find it. This guide explains it plainly.

Why lenders care

Knotweed spreads aggressively and can grow through hard surfaces and exploit weaknesses in structures. When a surveyor identifies it, they flag it to the lender, who then treats the property as carrying a risk. Until that risk is documented and managed, many lenders will not lend.

What lenders typically require

Most mainstream lenders will proceed if one of the following is in place:

1. A professional treatment plan with an insurance-backed guarantee. This shows the knotweed is being controlled by a specialist, and that any regrowth within the guarantee period is funded.
2. Evidence of full excavation and removal. If the knotweed has been dug out and disposed of legally, with documentation, the obstacle is removed.

A treatment plan *without* a recognised insurance-backed guarantee often will not satisfy them, which is the single most common reason a knotweed sale stalls.

Selling with knotweed

You must legally declare knotweed when selling — the standard property information form asks about it directly. Trying to hide it risks the sale falling through later, or a legal claim. The smoother path is to deal with it up front: get a survey, put a management plan and guarantee in place, and present the buyer with a documented, funded solution. A knotweed problem that is already being handled professionally is a far easier sale than one discovered mid-transaction.

The legal side, briefly

It is not illegal to have knotweed on your land, but you must not allow it to spread onto neighbouring property or into the wild — doing so can lead to civil claims. The plant and any soil containing it are classed as controlled waste. Both points are further reasons professional handling is the safe route.

If knotweed is holding up your sale or remortgage in Dover or East Kent, request a free survey and we will set out exactly what your lender is likely to need.