A rear extension in Chiswick begins with the existing back building line and the depth of the garden behind it. The area's Victorian and Edwardian houses often have generous rear plots, which can tempt an ambitious footprint, but the useful question is how far the extension can project before it erodes garden amenity, overshadows a neighbour or reads as an over-development of the plot. We test single-storey depths in section against the daylight reaching neighbouring windows and the position of the boundary, then set a projection that is both liveable and defensible when Hounslow assesses it.
The full-width rear extension is the workhorse of these houses. Removing the original rear closet-wing arrangement and pushing out the whole back of the house creates the garden-facing kitchen-dining-living room most owners are after, but it also concentrates the daylight and massing questions along the shared boundaries. We resolve the roof of that addition — a flat roof with a discreet parapet, a shallow mono-pitch, or a glazed lantern to bring light deep into the plan — so it sits below the original eaves and keeps the host elevation legible, which matters especially where the house lies within a conservation area.
A wraparound extension, taking in the side return as well as the rear, unlocks more floor area but raises the stakes on the boundary. The side element sits hard against a neighbour and changes the outlook along the shared edge, so we design the junction between the side and rear carefully and keep the roof low where it approaches the boundary. The wider footprint also means more of the garden is built on, so the balance between internal space gained and outdoor space lost is a design decision we test with the client before committing to a planning submission.
The choice between single and two storeys changes the assessment entirely. Single-storey rear extensions are judged largely on garden impact and neighbour daylight. A two-storey rear addition, realistic on some of the larger detached and semi-detached houses, brings first-floor windows, outlook and a sense of enclosure over a neighbour's garden into play, and is far more sensitive on a semi-detached pair where the two houses share a boundary. We advise early which storey height a given house and plot can carry before the design is developed for planning.
Daylight and right to light deserve attention early because Chiswick's terraces and semis sit close enough for a rear extension to affect a neighbour. Hounslow assesses daylight and sunlight to neighbouring windows using the established BRE tests, and a well-judged section — controlling height near the boundary and stepping the roof down — usually keeps a scheme within them. Right to light is a separate civil matter that a planning consent does not resolve, so where an extension approaches a neighbour's window we flag it so it can be addressed rather than discovered late.
From there the route is a coordinated one. We survey the house, test the extension against the planning, conservation and daylight constraints, and develop a design that a Hounslow case officer can support, then produce the planning drawings and, once the principle is settled, the building regulations package for construction. On the closely built Chiswick plots the Party Wall etc. Act usually applies, so we identify the notifiable neighbours early and coordinate with a party wall surveyor. The result is a rear extension that adds real family space without unbalancing the house or its garden setting.
