The right conversion is dictated by the roof you already have. A late-Victorian terrace off the Upper Richmond Road typically offers a rear slope where a dormer can add a full room without touching the front of the house, while the steeper-pitched Edwardian roofs of West Putney often convert more generously and can take a hip-to-gable move on a semi-detached pair. Many Putney terraces also carry a rear closet wing, and picking up its lower roof with an L-shaped dormer can turn one room into two. Where the property sits in a conservation street or faces the river, a prominent dormer is resisted and a rooflight-only scheme that keeps the roof shape becomes the sensible route. We match the option to your specific roof and its visibility, not to a house-type template, because the same conversion is not equally available on two roofs that look alike from the pavement.
Whether the loft is worth doing at all comes down to usable head height. You need enough clear height under the existing ridge that, once the new floor structure below and the insulated roof build-up above are added, the finished room holds a standing height across enough of its plan to live in rather than merely stand up along the centre line. Putney's steeper Edwardian roofs tend to deliver this comfortably; some shallow-pitched terrace roofs and later mansion-block roofs near the river do not, and there the ridge height and pitch decide whether you gain a proper bedroom or an awkward space squeezed under the slopes. A dormer can recover height and floor area over part of the plan where the raw roof falls short, which is one reason the head-height check and the roof form are settled together. We measure this at survey so the decision rests on the actual section, not an optimistic assumption.
The new staircase is the move owners most often underestimate, and on a compact Putney terrace it frequently decides the whole scheme. It has to rise from the floor below within the going and rise limits of the building regulations and land with full headroom over the top step, and that landing almost always eats into a bedroom or a landing on the storey beneath. On a narrow terrace plan there is rarely spare width, so the stair position governs both what you lose downstairs and whether the roof space is worth converting; a poorly placed flight can strand the very floor area the conversion was meant to create. We fix its route at feasibility, before the roof design, because everything above it depends on where it can physically go, and we test more than one option so the compromise on the floor below is a chosen one rather than an accident.
Fire escape is the requirement that reshapes a scheme if it is left late. Taking a two-storey Putney house up to three storeys lifts the new floor above the height at which the building regulations demand a higher standard: a protected stair enclosure running the full way down to a final exit, fire-rated doors to the rooms opening off it and mains-powered, interlinked smoke alarms through the house. Period terraces with knocked-through ground floors, which are common here, often cannot enclose the stair cleanly without undoing the open living space owners value, so a compliant alternative — a sprinkler or mist system, or a suitable secondary means of escape — is designed in from the start. We build the escape strategy into the drawings rather than letting building control impose one after the layout is set, because retrofitting fire separation into a finished plan is the most disruptive way to discover it.
A converted roof needs new structure, and in a terrace that structure lands on the neighbours. New beams typically span the house and bear onto the flank and party walls, with alterations to the ridge, purlins and rafters that a structural engineer designs and calculates. Because those bearings sit on the shared walls, the Party Wall etc. Act 1996 applies and notices go to the houses on either side before work begins, which is separate from the planning decision and best programmed early so it does not hold up the build. The roof is also where the insulation is brought up to current standards, whether between and over the rafters or within a warm-roof build-up, and where new drainage for a loft bathroom has to be routed down through the house to an existing soil stack — a detail that is far easier to place at design stage than to retrofit once the roof is closed up.
In a flat or mansion block the roof space raises an ownership question before any of the above. Putney has an unusually high share of purpose-built mansion blocks and converted flats, and the airspace above the top flat is very often retained by the freeholder, with the building's structure a shared interest. So a top-floor conversion depends on freeholder consent — usually a formal licence to alter — as well as the planning application, and because flats carry no permitted-development rights the planning route is always a full application. The final sign-off rests with both the freeholder and the council. We establish who owns the roof space and whether consent is realistically obtainable at the outset, because it is the gate the rest of the project passes through. On a house the equivalent early check is simply confirming the conservation position and the escape route before the design commits.
