Where knotweed grows in Cardiff: the postcodes we visit most
Roath, Grangetown, Llandaff North, Splott — a working surveyor's map of where Cardiff's knotweed actually lives.
We surveyed 412 Cardiff properties in 2025. Knotweed isn't randomly distributed — it follows the city's rivers, its old railway corridors, and the back lanes of its Victorian housing stock. Here is where we go most often.
The river corridors
The Taff from Llandaff Weir down to the Bay, and the Ely from St Fagans through Leckwith, are the two single largest seed and rhizome reservoirs in the city. Properties within 100 m of either riverbank account for roughly 38% of our Cardiff instructions.
The hot postcodes (CF24, CF11, CF14)
- CF24 (Roath, Adamsdown, Splott) — Victorian terraces with back lanes; classic spread route.
- CF11 (Grangetown, Riverside, Canton) — Ely and Taff influence, plus old industrial land.
- CF14 (Llandaff North, Whitchurch) — Taff corridor, larger gardens, mature stands.
- CF5 (Fairwater, Ely) — railway and river combined.
- CF3 (Rumney, St Mellons) — Rhymney river corridor and former industrial sites.
The back-lane pattern
Cardiff's terraces almost all share a rear access lane. Knotweed loves these — undisturbed soil, full sun in summer, no maintenance, and a continuous corridor along which rhizome can run from garden to garden. We routinely treat three or four neighbours' gardens off a single back-lane survey.
If you're buying in Cardiff
Ask your surveyor specifically to inspect the back lane and the immediate neighbours' gardens — not just the property line. A knotweed clump 8 m the wrong side of a fence will still affect your mortgage if it has crossed onto your soil.
Reviewed by
The survey team
PCA-certificated surveyors, Japanese Knotweed Elimination
PA1 / PA6A certificated surveyors who carry out the site visits, write the management plans and sign off the reports issued to lenders and solicitors.
Reviews the technical, legal and lender statements in this article.
What this page can't tell you
- Guidance is general. Identification, treatment choice and timescales can only be confirmed by a site visit — photographs alone are indicative.
- Lender and insurer requirements vary by institution and change over time. We state what is typically accepted, not what any named lender will accept on your case.
- Guarantee (IBG) eligibility depends on the plan chosen, the survey findings and the underwriter's acceptance. It is not automatic.
- Legal points summarise published law and guidance current at the review date. They are not legal advice.
Last reviewed · Questions on anything stated here: 07582 869979
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