Double-storey side extension, Stratford

Brief

A 1952 post-war council-built semi-detached in Forest Gate, Newham — E15, not in a conservation area, PD rights intact. The property had been purchased privately and was a straightforward mid-century spec: 84m² floor area, three bedrooms, one bathroom, narrow galley kitchen. The clients — a growing family — wanted to maximise the side plot (2.4m-wide driveway) and create a family-scale kitchen-diner on the ground floor and a master suite on the first floor.

Challenge

The 2.4m side plot was the tightest viable width for a double-storey side extension — the ground-floor kitchen needed to achieve at least 3m internal width (allowing a 3m kitchen run with a 900mm kitchen island). The party boundary on the north side required a Party Wall Notice to the neighbour; the shared driveway access to both properties' rear gardens (an easement in the title deeds) created a further access complication — the build could not permanently block the neighbouring access route. Foundation design: the site is in the Thames Estuary alluvial flood plain; ground investigation revealed London Clay at 1.1m depth overlying made ground — standard strip footings at 1.2m depth were acceptable. However, the made-ground layer (0–1.1m) contained fragments of wartime demolition rubble (tiles, brick) requiring careful excavation and material removal (classified as potentially contaminated fill — Environment Agency guidance). Newham Building Control required a contamination report before foundations were commenced.

Solution

Party Wall: Party Wall Notice served 2 months before start; neighbours appointed an Agreed Surveyor (the same as Builderr's surveyor); Award sealed in 5 weeks. Driveway access: maintained throughout construction by limiting scaffold to the inner 1.5m of the site during the build phase — the outer 900mm of driveway remained clear for access; scaffold removed from driveway after roof completion. Contamination report commissioned from a Phase 1 / Phase 2 environmental consultant (£2,400); report confirmed no significant contamination beyond inert demolition material — Newham Building Control satisfied at 3 weeks. Foundation: 450mm-wide strip footings at 1.2m depth on London Clay — standard. Ground floor: 2.4m plot gave 2.1m internal width of extension (after 150mm cavity wall each side) — insufficient for a kitchen run + island. Design solution: the ground floor extension fills the full 2.4m but the internal layout uses a 600mm structural post at the south end (bearing on the new foundation) to allow a 3.2m internal clear width for the kitchen zone — the post is incorporated into a kitchen island structure. Result: 28m² open-plan kitchen-diner with 4.8m south-facing bifold wall to garden. First floor: full-width master bedroom 2.1m × 9m = 18.9m² + 3.5m² walk-in wardrobe + 4.5m² en-suite shower room. Extension tied into existing host property at first-floor level using structural steelwork (203mm × 133mm UC) spanning the party wall opening. EV charger: 7kW Type 2 charger installed on the front elevation (OZEV grant, Ohme Home Pro) — Newham has one of the lowest EV charger penetrations in London; Builderr included this as part of the M&E scope.

Outcome

Floor area added: 48m² (28m² ground floor kitchen-diner + 20m² first-floor master suite including WI wardrobe and en-suite). Property uplifted from 84m² to 132m² — a 57% increase in floor area. The three original bedrooms retained; the master suite on the first floor extension freed up a bedroom for an additional child's room. EPC: unchanged at D (63) — the extension is built to current Part L standards but the host property remains uninsulated solid-wall construction (retrofitting the host is a planned phase 2). EV charger commissioned; Ohme/Octopus Go integration running at 7p/kWh overnight. Build completed 16 weeks, within the programme. Newham Building Control issued completion certificate at week 17.