A rear extension in Shepherd’s Bush starts with the existing rear building line and the depth of garden behind it, and that starting point differs across the stock. The dominant two-storey bay-fronted terraces usually have a modest back garden and an original rear outrigger — the projecting back-addition wing that once held the scullery — so the rear elevation you are extending is rarely a flat wall. The flat-fronted workers’ terraces and cottages are tighter and shallower again, which sets a lower ceiling on how far anything can go. The useful question is never how large the footprint could be, but how far the new work can project past that stepped rear line before it erodes the usable garden or overshadows the house next door. We survey the existing rear precisely first, because a projection that reads well on a wide bay-fronted plot can be undeliverable on a narrow cottage, and the decision has to be made against the real dimensions rather than a hoped-for room size.
Full width is what marks a rear extension out from its side-return neighbour. Where a side-return scheme only fills the narrow alley beside the original outrigger, a rear extension pushes the whole back elevation out onto the garden, running flank wall to flank wall and squaring off the L-shaped plan behind the house. That fuller form gives a much broader room, but it is also more sensitive at planning: it presents one continuous new face to the neighbours on both sides at once. We frequently hold the depth where the room actually needs it and set the outer corners in from a boundary, or step the roof down near a party wall, so the width is gained across the middle without pulling light off either neighbour. On an end-of-terrace house the calculus loosens, because only one flank abuts a neighbour and the other opens to a side return or a road, which can allow a deeper or wider addition than the equivalent mid-terrace can defend.
Overshadowing is the constraint that decides most of these schemes, because Shepherd’s Bush gardens are short and the terraces sit close. Hammersmith & Fulham assesses daylight and sunlight to neighbouring rear windows using the established BRE tests, and the depth an extension can carry is effectively set by the angle taken from the nearest affected window rather than by the length of your own garden. A well-judged section — keeping the parapet low near the boundary and letting the roof fall away from the party wall — usually keeps a scheme inside those tests. The neighbour worst affected is typically the one whose own outrigger or ground-floor window sits closest to your new flank, so we identify that critical window at the outset and design the height and depth around it rather than discovering the problem at consultation. Right to light is a separate civil matter that a planning consent does not settle, so where the addition approaches a neighbour’s window we raise it early rather than let it surface mid-build, when it is far more disruptive and expensive to resolve.
Whether an application is even needed comes down to the address. On an unrestricted house, some single-storey rear extensions can proceed under permitted development, but across the Wells and Askew conservation areas those rights are commonly stripped out by Article 4 direction, and any house long ago split into upper and lower flats has no permitted development at all. We therefore treat the full householder application as the default here, confirm the conservation and Article 4 position for the exact house before drawing anything, and, on the rare terrace where rights look intact, secure a Lawful Development Certificate so the position is certain rather than assumed. Even where permitted development does survive, the larger single-storey rear extension carries a prior-approval step that brings both neighbours into a formal consultation, so on a tightly packed terrace it rarely sidesteps the scrutiny a full application would attract, and we weigh that against the certainty a planning permission gives before recommending a route.
A full-width rear extension needs real structure, because opening the back of a terrace removes load-bearing wall. That usually means a steel frame — a goalpost or a pair of beams — carrying the masonry above the new opening and the outrigger return, designed and calculated by a structural engineer. On a mid-terrace house the new flank walls and their foundations sit on or beside a party wall on each side, and the foundations frequently fall within three or six metres of a neighbour’s structure, so the Party Wall etc. Act 1996 is engaged in both directions. Older terraces here often sit on shallow Victorian footings, so the new foundations may need to go deeper than the neighbour’s existing ones, which is exactly the condition the Act’s three-and-six-metre notices are written to cover. We resolve where the extension bears, keep its height down at each boundary to protect the neighbour’s light, and run the party wall notices alongside the planning drawings so neither process stalls the other.
The roof and the materials are where the addition is won or lost against a Victorian rear elevation. A flat roof with a discreet parapet, a shallow mono-pitch falling away from the party wall, or a glazed lantern set into the slab each suit different houses, and the right choice depends on the sill and head heights of the existing rear windows and how the extension is seen from neighbours’ upper floors. Against London stock brick we decide whether to match the brick, render, or introduce a restrained contemporary element, and detail the junction with the original wall so the new work reads as subordinate. From there the route is a coordinated one: survey, planning drawings a Hammersmith & Fulham officer can support, then the building regulations package covering structure, drainage, insulation and weathering for construction.
