Japanese Knotweed and Property Sales
There is a widespread belief that having Japanese knotweed on your land is illegal, however it is not. The risk lies in what you say about it in the Property Information Form.
Sellers are asked whether the property is affected, with the options “yes”, “no” and “not known”, and whether there has been a survey or management plan. The Law Society acknowledges the difficulty in their explanatory notes: a property is generally treated as at risk if knotweed is growing on it or within three metres of the boundary. Even where nothing is visible above ground, dormant roots or rhizomes may still be in the soil. For that reason, the notes acknowledge that many sellers answer “not known”.
Answering “No”
“No” is a positive statement that there is no knotweed. If that proves false and the buyer relied on the answer when purchasing, the seller may face a claim in misrepresentation.
Answering “Not Known”
If you genuinely do not know, “not known” is the honest answer. It shifts the burden of investigation onto the buyer, who can commission a specialist survey. But it cannot conceal knowledge you already possess. A seller with knowledge of previous treatment in the past cannot fairly describe the position as “not known”.
Answers must also remain up to date. If knotweed appears, or you learn something new before exchange, tell your solicitor so the buyer can be informed. Executors and attorneys should also take care as they remain responsible for the answers they provide, even if they have never visited the property.
Knotweed Crossing a Boundary
There is a separate risk where knotweed spreads to neighbouring land. In Network Rail Infrastructure Ltd v Williams [2018] EWCA Civ 1514, the Court of Appeal confirmed that physical damage is not necessary for a nuisance claim.
Encroaching roots can interfere with a neighbour’s use and enjoyment of land. Liability may arise where the owner knows, or ought to know, of the risk and fails to take reasonable action.
Mortgages and Surveys
Knotweed does not automatically make a property unmortgageable. Mortgage retention is generally associated with more serious cases, such as structural damage or restrictions on garden use. Knotweed visible on neighbouring land within three metres does not ordinarily trigger retention, although lenders may have their own requirements.
If knotweed is identified during a sale, consider a specialist survey by a contractor accredited by the Property Care Association or the Invasive Non-Native Specialist Association. Where treatment is required, obtain a written management plan with an insurance-backed guarantee, typically transferable to the buyer. A documented, guaranteed infestation can be managed and sold whereas an undisclosed one can result in litigation.
It is important to understand the potential liability arising from your answers to the Japanese Knotweed question in the Property Information Form, particularly as the buyer may rely on your answers long after completion. If Japanese knotweed is or may be present at a property you are selling, or if you are unsure on how to answer questions 8.6 and 8.7 accurately and honestly, you should seek advice from your solicitor before signing and returning the form.
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