Can You Get a Mortgage on a House With Japanese Knotweed?

Published by PCA Certified Survey Team • Updated October 2026

Short answer: often, yes. Japanese knotweed used to stop many mortgage applications outright, but most UK lenders now assess it case by case. What they usually want is evidence that the infestation has been professionally assessed and is being managed. Lender criteria vary, so always confirm with your broker or lender.

1. How Valuers Assess Knotweed

Since the RICS guidance published in 2022, surveyors assess whether knotweed is within the property boundary and whether it is within 3 metres of the habitable building, rather than relying on the older 7-metre rule. They then place the site into a management category, which lenders use to decide what conditions to apply.

2. What Lenders Typically Ask For

• A specialist survey from a qualified contractor, ideally a Property Care Association (PCA) member.
• A treatment and management plan covering herbicide treatment or excavation over several seasons.
• A guarantee, commonly an insurance-backed guarantee (IBG) of around 10 years, so the plan stays protected if the contractor stops trading.

3. If You Are Buying

If the seller's TA6 form or your survey mentions knotweed, ask for the existing management plan and guarantee and check they transfer to you. Your solicitor can raise enquiries, and you may be able to renegotiate the price to reflect treatment costs.

4. If You Are Selling or Remortgaging

Start treatment before you go to market. A plan already in place, with a transferable guarantee, is far easier for a buyer's lender to accept than an untreated stand discovered at valuation. Never conceal knotweed: misrepresentation on the TA6 form can lead to claims after completion.

5. Will It Affect the Value?

Some loss of value is possible, especially where knotweed is close to the house, but a documented plan and guarantee typically reduce the impact. A specialist report gives your valuer the facts they need instead of a worst-case assumption.