How much does a Japanese knotweed survey cost?

A Japanese knotweed survey usually costs £150–£500. Surveys by Property Care Association (PCA) accredited firms typically start at around £250–£299 plus VAT. If knotweed is found, a management plan with an insurance-backed guarantee is a separate and much bigger cost, often £1,500–£5,000 or more.

Typical Japanese knotweed costs

These are typical ranges from UK price guides and specialist firms, not quotes. Large gardens, commercial sites and London properties are usually at the top of the range.

What a survey includes

A specialist will normally:

• inspect the property and garden, and look over the boundary at neighbouring land;
• map and photograph any knotweed found;
• assess it using the RICS management categories (A to D) that lenders and valuers use;
• recommend treatment, and say whether a mortgage lender is likely to need a treatment plan.

The site visit usually takes about an hour, and the written report follows within a few days.

Why landlords care about knotweed

Mortgages and remortgages. Lenders are more flexible than they used to be, but each sets its own rules. Since 2022, RICS guidance has replaced the old “seven metre rule” with four categories:

For categories A and B a lender may ask for a specialist survey and a treatment plan, often with an insurance-backed guarantee. Category C usually goes ahead without a retention.

Selling. The TA6 property information form, which sellers fill in through their solicitor, asks whether the property is affected by Japanese knotweed. If you know it is there, say so. A buyer who relied on a false answer can sue.

Neighbours. In Network Rail v Williams (2018), the Court of Appeal held that knotweed on one property that affects a neighbouring property can be an actionable private nuisance, even before it causes physical damage. If knotweed spreads from your rental into next door, you could face a claim. If it is coming in from a neighbour’s land, a survey report is useful evidence.

Tenants. Tenants may not recognise knotweed. Ask them to report unusual plant growth, and tell them not to cut, dig up or compost it.

The legal position

In England, the GOV.UK guidance on preventing Japanese knotweed from spreading says:

• it is not illegal to have Japanese knotweed on your land, and you do not legally have to remove it unless it is causing a nuisance;
• you must stop it spreading off your property;
• you can be prosecuted for causing it to spread into the wild, which is an offence under section 14(2) of the Wildlife and Countryside Act 1981;
• soil or plant material contaminated with knotweed may be classed as controlled waste. If it leaves the site, it must go with a registered waste carrier to an authorised landfill site. It must not be mixed with other surplus soil or sold as topsoil.

Scotland, Wales and Northern Ireland have their own guidance, so check the rules for the nation where your property is.

Who to use

Use a firm accredited by the Property Care Association (PCA). Lenders usually want a treatment plan from an accredited specialist, backed by an insurance-backed guarantee that stays with the property if you sell. Ask what the guarantee covers, how long it lasts and whether it transfers to a buyer.

Ways to keep the cost down

• Survey before you buy. If the seller’s TA6 says “yes” or “not known”, a survey lets you factor the treatment cost into your offer.
• Act early. A small, recently established stand is cheaper to treat than one that has spread for years.
• Don’t disturb it yourself. Cutting or digging can spread fragments and make treatment longer and dearer, and disposal mistakes can be an offence.
• Compare the guarantee, not just the price. A cheaper treatment plan whose insurance-backed guarantee is short or doesn’t transfer to a buyer may not satisfy a lender, leaving you to pay for a second plan when you remortgage or sell.
• Keep the paperwork. A treatment plan, guarantee and completion certificate make the property easier to remortgage or sell. Our landlord compliance checklist covers what else to keep on file.