Flood risk assessment + Environment Agency zones + sequential test + Class MA exception
Flood risk under Town and Country Planning (General Permitted Development) (England) Order 2015 Schedule 2 Part 3 Class MA paragraph MA.2(1)(c) requires LPA to determine 'flooding risks'. Tested per Environment Agency Flood Map for Planning (latest update typically Q3 + Q4 annually + revised after material events). Flood zones: Zone 1 — low probability less than 1 in 1,000 annual probability flooding from rivers or sea; Zone 2 — medium probability 1 in 1,000 to 1 in 100 annual probability rivers / 1 in 1,000 to 1 in 200 sea; Zone 3a — high probability 1 in 100+ annual probability rivers / 1 in 200+ annual probability sea; Zone 3b — functional floodplain (most extreme flooding); + Surface Water Flood Risk Zones (1 in 30 / 1 in 100 / 1 in 1,000 surface water from Lead Local Flood Authority maps); + Reservoir Flood Risk (if any reservoir within 25km of site); + Groundwater Flood Risk (rising groundwater table). London-specific flood risks: River Thames + tidal floodplain (Thames Barrier protects up to 1 in 1,000 standard but climate change scenarios increase risk by 2050–2100); River Lee / Lee Valley (north-east London); River Wandle (south-west); River Roding (east); River Brent (north-west); River Crane (Heathrow area); + extensive surface water flood risk maps + 30+ underground rivers (Fleet, Tyburn, Westbourne, Walbrook, Effra, Falconbrook, Stamford Brook, Counter's Creek, Hackney Brook, Wandle distributaries). Flood Risk Assessment requirements per zone for Class MA: Zone 1 — generally not required unless surface water flood risk identified or site over 1ha (rare for Class MA which is typically less than 1,500m² = 0.15ha); Zone 2 — site-specific FRA required per NPPF Annex 3 + PPG Flood Risk + Coastal Change — flood-resilient design (e.g. ground floor levels above 1-in-100 design flood event), sequential test (would site be allocated under sequential test? — usually yes for brownfield Class MA), exception test (would benefits outweigh flood risk?); Zone 3a — site-specific FRA + sequential test + exception test + more onerous flood-resilient design including evacuation route, flood-resistant materials below design flood level, finished floor levels typically +600mm above flood level; Zone 3b functional floodplain — Class MA effectively impossible (residential not appropriate in functional floodplain per PPG). Class MA + flood: LPAs apply the sequential test less strictly to Class MA (because reuse of existing building is generally preferred) — typically Zone 2 + 3a Class MA prior approvals granted with conditions on finished floor levels + flood-resilient ground floor materials + flood evacuation route + flood warning subscription. Refusal grounds flood: site cannot demonstrate adequate flood mitigation + safe evacuation; ground-floor flats in Zone 3a without raising floor levels above flood level; basement flats in any flood-risk zone (rarely granted). Builderr workflow flood: Month 0 pre-app — Environment Agency Flood Map check + Lead Local Flood Authority surface water check + RAG status flagging; Zone 1 = green (no FRA); Zone 2 = amber (FRA £950–£2,500); Zone 3a = red (FRA £2,500–£6,500 + likely design changes raising ground floor or flood resilience); Zone 3b = abort or full planning with substantial flood mitigation.
Noise + contamination assessment + Builderr workflow + cost + risk + appeal route
Noise impact under Class MA paragraph MA.2(1)(d) requires LPA to determine 'impacts of noise from commercial premises on the intended occupiers of the development'. Tested per Professional Practice Guidance: Planning + Noise — New Residential Development (Pro PG ANC 2017, Association of Noise Consultants + Institute of Acoustics + Chartered Institute of Environmental Health) + BS 8233:2014 Guidance on sound insulation + noise reduction for buildings + WHO Community Noise Guidelines 1999. Internal noise targets habitable rooms (BS 8233:2014): living rooms 35 dB(A) Leq daytime / 30 dB(A) Leq night; bedrooms 35 dB(A) Leq daytime / 30 dB(A) Leq night + 45 dB(A) LAmax,F night for max events. External noise targets: gardens + balconies 50 dB(A) Leq daytime. Noise sources London Class MA: (a) traffic on adjacent A-road / arterial road / motorway (M25, M4, M11, M1, A1, A2, A3, A20, A23, A40, A406, A205) — typical façade level 65–75 dB(A) Leq day at 4m setback — needs 30–40dB(A) reduction = high-performance double or triple glazing + acoustic ventilation; (b) railway lines (London Overground, Underground subsurface, National Rail) — typical façade level 55–80 dB(A) Leq day + LAmax,F freight 90–100 dB(A) — needs acoustic glazing + secondary glazing + ventilation isolation; (c) Heathrow / City flight paths — typical façade level 50–65 dB(A) Leq day — needs sealed double-glazing + MVHR not natural ventilation; (d) adjacent commercial premises — pubs, restaurants, takeaways, gyms, nurseries, music venues — variable from 35–95 dB(A) depending on operation + opening hours; (e) industrial/light industrial Class E neighbours; (f) HVAC plant + chillers on adjacent commercial roofs. Class MA conversions in mixed-use Town Centre locations almost always require noise impact assessment due to adjacent commercial uses sharing party wall / floor / yard. Cost: noise impact assessment Class MA £1,250–£2,500 (Hoare Lea, RPS, WSP, Anstey Horne, 24Acoustics, Bickerdike Allen). Refusal grounds noise: internal levels exceeding 35/30 dB(A) without practical mitigation; adjacent commercial use (e.g. nightclub, music venue, late-night takeaway) where occupants would suffer regular sleep disturbance; cumulative noise from multiple sources cannot be reasonably mitigated. Mitigation: high-performance triple glazing (Reynaers MasterLine 75 / Schueco AWS 70 BS / Smart Architecture System with 6-12-4-12-6 acoustic glazing pack achieving 40+ dB Rw reduction); acoustic ventilation (Renson Sonik or Roxa AAV achieving 35 dB Dnew); sealed envelope + MVHR (Zehnder ComfoAir or Vent-Axia Sentinel Kinetic + heat recovery 90%+); orientation strategy (bedrooms to quiet side, living + kitchen to noise-affected side); buffering use (corridor / bathroom / storage between noise source + habitable room); set-back balconies; planting + acoustic screens to balconies. Contamination assessment under Class MA paragraph MA.2(1)(b): LPA determines 'contamination risks on the site'. Tested per Part 2A Environmental Protection Act 1990 + NPPF paragraph 184 + Land Contamination Risk Management LCRM (Environment Agency 2020). Required for: (a) sites with previous industrial use (factory, workshop, garage, petrol station, dry cleaner, photographic studio, tannery, chemical works, gasworks, foundry, printing works); (b) sites within 250m of historic landfill; (c) sites with known contamination history (former petrol stations + dry cleaners = priority risk). Phase 1 desktop study (typical £950–£2,500) covers: historic maps Goad / Ordnance Survey 1860–1990 + Envirocheck reports + Environment Agency Local Authority + Drinking Water Inspectorate records + radar/LiDAR + site walkover + risk assessment + recommendations. Phase 2 intrusive investigation (typical £4,500–£18,500): boreholes + trial pits + ground gas monitoring + groundwater sampling + soil testing for heavy metals + PAH + volatile organic compounds + asbestos in made ground. Phase 3 remediation strategy if contamination identified: typical interventions cap-and-cover with 600mm clean cover (cost £25–£85/m²); ground gas membrane Visqueen GM3 (cost £18–£38/m²); soil removal + disposal (£85–£280/m³ depending on hazard classification); vapour mitigation barriers (£35–£85/m²). Refusal grounds contamination: site unacceptably contaminated + no practical remediation; ground gas risk uncontrolled (radon, methane from landfill); groundwater contamination affecting water supply. Builderr workflow: Month 0 pre-app — desktop contamination history check (free Envirocheck Light report) + risk RAG status; low risk (no industrial history within 250m + Greenfield Use) = no Phase 1 needed; medium risk (former retail/office, suburban) = Phase 1 desktop £950; high risk (former petrol, dry cleaner, industrial) = Phase 1 + Phase 2 intrusive £4,500+ pre-submission; Month 1–2 Phase 1 / Phase 2 reports; Month 2 prior approval submission with reports. Appeal route flood/noise/contamination refusal: same as other Class MA refusals — s78 appeal to PINS within 6 months — typically 60–70% overturn rate if refusal evidence weak. Builderr cost-of-failure: refusal on these grounds usually means design fix exists (raise floor for flood, acoustic glazing for noise, cap-and-cover for contamination) — refusal sometimes appeal-resolvable but more often redesign + resubmit faster + cheaper. See [[class-ma-office-to-residential-conversion-london]] + [[class-ma-prior-approval-process-london]] + [[asbestos-survey-cost-london-renovation]] + [[flood-risk-assessment-london-renovation]].
