How do I check my flood zone?

Environment Agency Flood Map for Planning: gov.uk/check-long-term-flood-risk. Enter postcode — shows fluvial Flood Zones 1/2/3 + surface water + groundwater + reservoir risk. Free instant check. Builderr does pre-purchase flood check on any client's prospective site.

Will I get insurance in Flood Zone 3?

Yes via Flood Re scheme (Government-backed insurance reinsurer for high-risk homes, 2016–2039). Premiums capped at affordable level for residential in flood-risk areas. Post-Flood Re (2039), market expected to require flood-resilient construction for cover.

Can I extend a house in Flood Zone 3?

Possible but constrained. Need FRA showing extension does not increase flood risk to others + extension itself safe (raised FFL + resilient construction). Conversions of upper floors (loft conversion) generally easier than ground-floor extensions. Builderr's Greenwich Maritime + Tower Hamlets Spitalfields case studies in Flood Zone 2/3 — both proceeded with FRA + raised FFL + flood-resilient construction below ground floor.

Flood Risk Assessment London 2026 | Builderr

Do I Need a Flood Risk Assessment for a London Renovation?

Flood Risk Assessment (FRA) required for planning applications in Environment Agency Flood Zone 2 or 3, sites 1 hectare+ in Flood Zone 1, or with other flood risk indicators (surface water, groundwater, sewer flooding). NPPF + Local Plan policy. Cost £950–£3,850 by qualified hydrologist. Affects London Thames + Lea + Wandle + Beverley Brook floodplain locations.

When FRA required

NPPF Annex 3 + Local Plan policy require FRA for planning applications: (1) in Flood Zone 2 (1-in-1000 to 1-in-100 year annual probability river/sea flooding); (2) in Flood Zone 3 (1-in-100 year+ probability); (3) on sites 1 hectare+ regardless of zone (surface water assessment); (4) with critical infrastructure (electricity, water, hospital) at risk; (5) within Critical Drainage Areas (CDA) per Lead Local Flood Authority maps; (6) involving change of use to more vulnerable category. Check Environment Agency Flood Map (gov.uk/check-long-term-flood-risk) by postcode. London areas in Flood Zone 2/3: Thames foreshore (Westminster, Tower Hamlets, Newham, Greenwich); Lea Valley (Hackney, Waltham Forest); Wandle Valley (Wandsworth, Merton); Beverley Brook (Wandsworth, Richmond, Wimbledon).

FRA content + methodology

FRA per NPPF + Environment Agency Standing Advice + Local Lead Flood Authority guidance. Content: (1) Site location + topography + historical flood records; (2) Sources of flooding — fluvial (rivers/sea), pluvial (surface water), groundwater, sewer; (3) Flood probability + depth + velocity at site for design events (100-year + climate change allowance up to 70%); (4) Vulnerability classification of development (residential = More Vulnerable); (5) Sequential Test (is there alternative lower-risk site? — for new development only); (6) Exception Test (do public benefits outweigh risk + can development be safe?); (7) Mitigation — Finished Floor Level (FFL) raised above design flood + climate change; flood-resilient construction (concrete floor, water-resistant render below FFL, electrics at raised height); SUDS for surface water; evacuation route. Cost £950–£2,850 typical residential; £2,850–£8,500 complex sites.

Mitigation strategies for residential renovation

Raised FFL: minimum 600mm above design flood level (200-year + climate change for most London) — practical impact varies (some sites need 300mm above existing ground; some need 1.2m above). Flood-resilient construction: concrete ground floor instead of timber suspended; closed-cell insulation below FFL (resists waterlogging); water-resistant render (Sika RenderTec) below FFL; electrical sockets + consumer unit at 1.2m+ above FFL; appliances above FFL or movable. SUDS: permeable paving + soakaway + rain garden + green roof for surface water management. Property Flood Resilience (PFR) measures: flood doors, air-brick covers, non-return valves on drainage, sump + pump systems. London-Wide Strategic Flood Risk Assessment + borough Local Flood Risk Management Strategies guide local approach.