Japanese knotweed disclosure under TA6: what to ask

Japanese knotweed disclosure on the standard Law Society TA6 (Property Information Form) sits at section 7.8: "Is the property affected by Japanese knotweed?" The seller answers Yes / No / Not Known. A Yes triggers follow-up questions: when the seller became aware, what treatment has been done, who carried out the treatment, and whether a Management Plan exists.

What to ask + look for as a buyer or surveyor:

1. **The Property Care Association (PCA) certificate or insurance-backed guarantee.** Reputable knotweed-treatment firms issue a 5-10 year insurance-backed guarantee covering re-emergence. Without one, the treatment evidence is weak.

2. **The Management Plan.** A documented schedule of monitoring + treatment. RICS guidance recommends a Management Plan run for at least 3 years post-final-application of herbicide.

3. **The 7-metre boundary check.** Knotweed regrows from rhizome fragments + crosses property boundaries. Surveyors check the 7-metre boundary on either side of the property line, since rhizome can remain dormant + reactivate.

4. **The mortgage lender's stance.** Most major UK lenders accept treated knotweed with a PCA-grade guarantee. Some will not lend on untreated knotweed at all. Check the panel rules.

5. **Visual inspection.** Active knotweed stalks are reddish/purple, hollow, with heart-shaped leaves alternating in a zig-zag pattern. Best identified May-September. Surveyors photograph any suspected stand for the report.

For postcode-area context, the Stratum postcode-intelligence API returns a knotweed band proxy from INNS / iRecord aggregates. The disclaimer is explicit: the band is NOT a property-level survey — it's a background-rate signal that helps prioritise the surveyor's site visit. The TA6 disclosure + a chartered surveyor field check remain the load-bearing checks at the property level.

Source: Law Society TA6 Form

Last updated 2026-05-06.