The right conversion depends entirely on the roof you start with, and Richmond's stock gives several starting points. The Victorian and Edwardian terraces typically carry a steep rear slope that suits a rear dormer, opening usable floor area at the back where it is least visible from the street. Semi-detached and end-of-terrace houses often have a hipped roof, where a hip-to-gable move squares off the end and then carries a dormer behind it. Where the roof is prominent or the setting sensitive, a conservation-style rooflight scheme keeps the existing shape and raises the fewest planning questions, at the cost of the least added head height. We match the form to the specific roof, not to a template, and we assess it against the neighbouring roofs on the same terrace, because a dormer that copies an established local pattern is easier to defend than one that introduces a form the street has never carried.
Whether a loft is worth doing usually comes down to head height under the existing ridge. As a working rule you want roughly 2.2 to 2.4 metres from ceiling joist to ridge before the new floor and insulation build-up, and the finished room has to hold a usable height across enough of its footprint rather than only along the centre line. Many Richmond period houses have generously pitched roofs that convert well; shallower or later roofs can leave you with a space you can only stand up in down the middle. We measure the ridge, the pitch and the existing structure at feasibility so the decision to proceed rests on the real geometry of your roof. Where the height is marginal, a rear dormer can recover usable width by lifting the ceiling at the back, whereas a rooflight scheme leaves the tight pitch as it is — so the head-height reading and the choice of form are settled together rather than one after the other.
The form of the dormer is where the conservation judgement bites. A rear dormer is generally kept subordinate — set down from the ridge, held in from the party walls at each side, and clad or slated to sit quietly against the retained slope rather than filling it. A full-width box dormer that swallows the whole rear plane reads as an over-development and is far harder to defend where PD rights have been removed. On a front or street-facing slope, and in views from the river, the Green or the hill, the roof is effectively part of the public townscape, so we keep visible change minimal and push the gain to the concealed rear where the setting allows.
The new staircase is the part owners most often underestimate. It has to rise from the floor below within the going and rise limits of Approved Document K and land with full headroom over the top step, and it almost always consumes part of a bedroom or the landing on the storey beneath. On a narrow Victorian terrace that space is tight to begin with, so the stair position frequently decides whether the conversion is genuinely worth doing. We resolve it at feasibility, because it governs both the cost to the floor below and how much of the new roof room you actually reach and use. Where a straight flight will not fit, a quarter-turn over the existing stairwell often recovers the space, but it has to land under the highest part of the roof so the headroom over the top step is compliant rather than notional, and that landing point in turn influences where the dormer has to go.
Fire escape is the requirement that catches people out. Turning a two-storey house into three lifts the new top floor above the 4.5-metre threshold and triggers a higher standard: a protected stair enclosure running to a final exit, fire-rated doors — typically FD30 — to the habitable rooms off it, and mains-powered, interlinked smoke alarms. In an open-plan period house the existing stair often cannot be enclosed cleanly, so an alternative such as a sprinkler or mist system, or a compliant secondary escape, has to be designed in. The escape windows and any dormer glazing also have to meet the emergency-egress dimensions, which can pull the dormer's size and cill height in a particular direction, so the fire strategy and the roof form are worked out together. We build all of this into the drawings from the start rather than leaving building control to reshape the layout late in the project.
A converted roof needs new structure, and on Richmond's terraces that structure lands on shared walls. Typically steel beams span the house at new floor level and alter the ridge, purlins and rafters, all designed and calculated by a structural engineer. On terraced and semi-detached houses those beams usually bear into the party walls, which engages the Party Wall etc. Act 1996, so notices go to the neighbours on either side before work starts — a matter separate from the planning decision and best programmed early. The roof is also where insulation is brought up to current standards, and where a house is listed the structural change to historic roof timbers is a consent matter as well as an engineering one.
