Single-storey rear basics
A single-storey rear extension projects from the rear wall of the house into the garden. The footprint is typically rectangular, running the full width of the existing rear wall (or partial width if a side return is not included). Depth varies: 3 metres is the standard permitted development limit, but the Larger Home Extension scheme allows up to 6m on detached houses and 8m on terraces and semis subject to prior approval — a lighter-touch consent process that takes 6 weeks. Roof type, glazing, kitchen layout and structural method all flow from these basic parameters.
Larger Home Extension prior approval
Introduced in 2014 and made permanent in 2019, the Larger Home Extension scheme allows single-storey rear extensions up to 6m (terrace/semi) or 8m (detached) under a prior approval process rather than full planning. The council notifies neighbours, who have 21 days to object on grounds of impact on amenity. If no objections are received, the extension is approved automatically. If objections come in, the council considers them and decides — usually within 42 days from submission. Approval rates are 75–80% across most London boroughs. We submit prior approvals on every eligible project and have a 91% approval rate.
Roof and natural light
Rear extensions of 5m+ depth need careful light planning because the rear of the original house becomes dark — the new extension covers what was a window or door wall. The two main strategies: a flat roof with one or two large roof lanterns (3m × 1.5m typical) positioned to wash daylight across the back of the original house, or a pitched glazed roof using a single-sided lean-to or a fully glazed pitched lantern. Both work; lanterns are cheaper and more common, glazed pitched roofs deliver more drama. We model daylight with SketchUp + V-Ray during design so you can see exactly what the finished space looks like at different times of day.
Structural approach
Where the existing rear wall is removed to open up the new extension into the original kitchen or dining room, a steel beam spans the full width to pick up the first-floor wall above. On a 5m wide opening this is typically a 305 UB section. Foundations are usually mass-fill concrete to 1m depth, deeper where mature trees are within 5–10m of the boundary (London clay shrinks and swells with tree water uptake — NHBC guidance dictates foundation depth based on tree species and distance). On heavy clay sites with multiple trees we use mini-piled foundations to derisk future ground movement.
Glazing strategies
The rear wall of a single-storey rear extension is typically 80–100% glazed. Standard configuration is a set of bi-folding or sliding doors across the width with a flanking fixed picture window where the wall is wider than the door opening. Crittall-style steel frames with multi-pane glazing deliver a distinctive aesthetic — we install Crittall, IDSystems and Fabco Sanctuary frames depending on budget and design intent. Glazing always uses double or triple glazing with low-emissivity coating and argon fill; structural glass roofs use laminated heat-soaked toughened panes for safety.
Kitchen, dining and living layouts
Most rear extensions support an open-plan kitchen-dining-living arrangement. The classic London layout is kitchen along one side wall, island parallel, dining table near the original rear wall, and a sofa zone behind. Underfloor heating runs throughout, allowing all wall space to be used for cabinetry, glazing or seating rather than radiators. We coordinate kitchen design and install with the build phasing so plumbing, electrics, gas and waste are all set out correctly before the floor screed pours.
Wraparound option
Where space permits, a side return can be combined with a rear extension into a single wraparound extension. This delivers the largest single-storey ground floor and is covered in detail on our dedicated wraparound extension page. The cost is roughly 30–40% higher than a side return or rear alone but the resulting space is significantly bigger than either component would deliver individually.
