The whole spectrum of house extension drawings — rear single-storey, side return, wraparound, double-storey rear and basement / lower-ground. Permitted Development, Prior Approval (Class AA) or Full Planning. Drawings, Building Regs, structural calcs and Party Wall — fixed fee from £1,225, MCIAT chartered.
Measured existing survey, photographic record, Article 4 and conservation check before we quote design.
2–3 design options at concept stage — we explore alternative layouts, glazing and roof forms before committing.
Site location plan, existing and proposed plans, elevations, sections, Design & Access Statement where required.
Part L thermal, Part B fire, Part M accessibility, structural strategy coordinated with engineer.
Steel beam, foundation, lintel design. Chartered engineer. Submitted to Building Control.
Party Wall notices where needed; Thames Water Build Over Agreement where you're within 3m of a public sewer.
London house extension drawings cluster into five common patterns. The right one depends on plot width, rear garden depth, planning constraints (Article 4, conservation area), neighbouring boundaries and budget. Below is the plain-English decision matrix, with the typical fixed fee for each.
Typical projection 3–6m off the back wall, full plot width. Permitted Development up to 3m (terrace) / 4m (detached); Prior Approval Class AA stretches to 6m / 8m. Best for: opening up kitchen-diners on Victorian and Edwardian terraces. Build cost typically £55k–£95k.
Typical width 1.8–2.2m, full depth of the original kitchen / outrigger. Usually Permitted Development on terraces (not flats, not Article 4). Best for: narrow Victorian terraces in Clapham, Hackney, Islington where the side alley is wasted square footage. Build cost typically £30k–£55k.
L-shaped extension combining a rear projection with the side return — usually 18–28m² of new floor space. Almost always exceeds PD cube limits, so needs Full Householder Planning (8-week determination). Best for: open-plan kitchen-living-dining on a Victorian terrace. Build cost typically £75k–£130k.
Adds a first-floor bedroom or bathroom over a rear extension. Permitted Development limited to 3m projection and must not exceed eaves height. Most schemes need Full Planning, especially within 2m of the boundary. Best for: 4-bed conversions to 5-bed on 1930s semis and Edwardian terraces. Build cost typically £85k–£140k.
Single-storey dig under the existing footprint, sometimes with a garden lightwell. Strict policies in Camden, RBKC, Westminster (no double-basements, depth limits); freer in outer boroughs. Best for: gaining a media room, gym or guest suite without losing garden. Build cost typically £3,500–£5,500 per m².
Most London house extension submissions complete in 18–25 working days from instruction. The council then takes 8 weeks on a Householder Planning application, 6 weeks on Prior Approval (Class AA), or 13 weeks on a major Full Planning scheme. Building Regulations Full Plans run in parallel and the structural pack lands on site with the contractor before week one of the build.
Days 1–3 — measured existing survey, photographic record, drainage check, Article 4 + conservation lookup.
Days 4–9 — 2–3 design options, massing and glazing studies, PD vs planning route confirmed, fixed quote signed.
Days 10–18 — site plans, elevations, sections, Design & Access Statement where required, Planning Portal lodgement.
Days 19–25 — Part L thermal, Part B fire, Part M access, steel beam and foundation calcs with chartered engineer.
Post-approval — three-builder competitive tender pack, Party Wall notices drafted, on-site queries answered during build.
Anonymised drawings from a wraparound rear + side return extension to a Victorian terrace in SW11. Householder Planning approved at delegated officer level in 7 weeks, followed by Full Plans Building Regulations submission with chartered structural engineer sign-off on the new steel goalpost frame and pad foundations.
Want the full PDF set? Start a free quote and we’ll email a redacted sample matching your extension type.
Planning drawings only — rear, side return or PD single-storey.
Planning + Building Regs + structural — wraparound, double-storey ready.
Planning + BR + structural + 3D visuals + tender support.
Three featured extension submissions across Greater London. Planning references verifiable on each council’s public portal — full case studies publishing shortly.
Victorian terrace, NW1. 2.1m side return + small rear projection inside a designated conservation area. Householder Planning approved with Heritage Statement and matching London stock brick. £62k build, completed in 14 weeks with steel goalpost frame.
Edwardian terrace, E8. 6m rear single-storey extension submitted under Prior Approval (Larger Home Extensions). No neighbour objections within the 21-day consultation, deemed approved at week 6. Full Plans Building Regs with bi-fold glazing and rooflights.
Victorian terrace, SW11. Full wraparound combining 3m rear projection with 2.0m side return — 22m² of new open-plan kitchen-dining. Full Householder Planning approved at delegated officer level with no amendments. Structural sign-off on steel goalpost and pad foundations.
Every case is different. Call +44 7592 201 353 for a five-minute chat.
Start a free quote →Single-storey rear extensions up to 3m (attached) or 4m (detached) fall under standard PD; up to 6m/8m under Prior Approval (Class AA). Side extensions up to half the width of the house. Not available on flats or in Article 4 areas.
Most outer boroughs allow single-storey basement. Camden, RBKC and Westminster have strict policies limiting basement depth and coverage. We advise on viability at the first site visit.
Usually to the full side-passage depth — typically 1.8–2.2m wide, running the full length of the original kitchen/dining area. Works best on Victorian/Edwardian terraces where the side return is otherwise wasted space.
A wraparound extension (rear + side) usually exceeds PD limits and requires full planning permission. Worth the effort — wraparounds unlock large open-plan kitchens in narrow Victorian terraces.
Budget £2,200–£3,500 per m² for London build costs (2026). So a 25m² rear extension is £55,000–£87,500 to build, plus our fees and council fees. We coordinate trusted builders.
Rear, side return, wraparound — watch how we design extensions that maximise space and get approved first time.
Our side return extension transformed the kitchen. The drawings showed exactly what we’d get, and the build matched perfectly. Worth every penny.
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