Japanese knotweed, mortgages and selling a house

At SE Knotweed, we unblock mortgages and sales held up by Japanese knotweed by producing the survey, management plan and insurance-backed guarantee that lenders and valuers require. Knotweed rarely stops a mortgage outright once the risk is shown to be managed.

Why does knotweed affect a mortgage?

Knotweed affects a mortgage because the lender's valuer flags it as a risk to the property, and the lender wants that risk managed before lending. The plant can spread and is expensive to remove, so the valuer looks for evidence that a specialist has assessed it and has a plan.

At SE Knotweed, we produce that evidence: a survey, a costed management plan and an insurance-backed guarantee. Get in touch if a valuer has flagged knotweed on a property you are buying or selling.

What do lenders want to see?

Lenders want to see a management plan from an accredited firm and an insurance-backed guarantee that would pay for further treatment if the knotweed returned. That guarantee reassures the lender because it moves the future risk off the property.

We write a mortgage-ready survey and report to the format a lender expects, setting out the RICS category, the plan and the guarantee term.

How does a guarantee unblock a sale?

An insurance-backed guarantee unblocks a sale because it is the document that lets a lender proceed even before treatment finishes. It commits an audited contractor to returning and re-treating at no cost if regrowth appears within the term.

The guarantee page explains what it covers, and because a plan can be produced within a week or two, the sale rarely has to wait for the full treatment.

Do I have to declare knotweed when selling?

You do have to declare knotweed when selling. Question 7.8 of the TA6 Property Information Form asks specifically about it, and since 2020 you may only answer No if you are certain there is no rhizome above or below ground or within 3 metres of the boundary.

A survey gives you the certainty to answer honestly, and answering No when knotweed is present can expose you to a misrepresentation claim later.

Does knotweed devalue a property?

Knotweed can affect a property's value while it is untreated, because a buyer and their lender price in the cost and the risk. A completed management plan and an insurance-backed guarantee usually restore lender confidence and most of the value.

The residual effect is often smaller than owners fear, and the diminution in value page explains what the courts have said about it.

How quickly can you help a stalled sale?

We can usually survey a property and issue the report and costed plan within a week, which is often enough for a lender to proceed. The treatment then continues after the sale completes, covered by the guarantee.

Contact us with the address and the lender's requirement, and we will set out exactly what they need to lend.

INSURANCE-BACKED GUARANTEE

The guarantee a lender accepts

An insurance-backed guarantee from an audited contractor commits to returning and re-treating at no further cost if regrowth appears within the term. It is the document that reassures a mortgage lender, because it moves the future risk off the property. The term is confirmed with your plan.

In this section

Common questions

Can you get a mortgage on a house with knotweed?
Usually yes, where there is a professional treatment plan and an insurance-backed guarantee. Most lenders lend against the property once those are in place.
Do I have to declare knotweed when selling?
Yes. The TA6 Property Information Form asks about knotweed, and since 2020 you may only answer No if you are certain there is no rhizome above or below ground or within 3 metres of the boundary.
Does knotweed devalue a property?
It can affect value while untreated, but a completed management plan and guarantee usually restore lender confidence. The residual effect is often smaller than owners fear.

Book a survey and get a costed plan

Tell us the address and what a surveyor flagged. We confirm the plant, record the RICS category and set out the figures.

Book a survey
Call 01924 944600