The right conversion starts with the roof you have. Many Hampstead Garden Suburb houses carry steep, tiled Arts-and-Crafts roofs with prominent gables and tall chimneys, and here a rear dormer set well into the back slope, or a rooflight conversion that keeps the roof shape entirely, usually reads far more comfortably than a mansard. The larger detached and semi-detached houses can sometimes suit a hip-to-gable move, but only where the pair's symmetry and the street's character can absorb it. We match the option to your specific roof and its place in the designed roofscape, rather than to a standard template.
Whether a loft is worth doing usually comes down to head height. As a rule of thumb you want roughly 2.2 to 2.4 metres under the existing ridge before the new floor build-up, held across enough of the plan to give a genuinely usable room. The Suburb's steep-pitched cottage and house roofs often convert well, with the ridge sitting high enough to gain a full storey; shallower roofs, and the lower cottage-flat blocks, can leave you standing full height only along the centre. We measure the roof and check the pitch at feasibility, before any design is committed.
The new staircase is the element owners most often underestimate. It has to rise from the floor below within the going and rise limits of Approved Document K, land with full headroom above it, and it almost always takes a slice of a bedroom or landing on the storey beneath. In a compact Suburb cottage or a cottage flat that space is tight and often already spoken for, so the stair frequently decides whether the conversion is worth doing at all. We fix its position at feasibility, because it governs both the cost to the floor below and how much usable room the roof finally delivers.
Fire escape is the requirement that catches people out. Turning a two-storey house into three lifts the top floor above the 4.5-metre threshold and triggers a higher standard: a protected stair enclosure running all the way to a final exit, fire-rated doors — typically FD30 — to the rooms off it, and mains-powered, interlinked smoke alarms. Older Suburb interiors that have been opened up over the years often cannot enclose the stair cleanly, so an alternative such as a sprinkler or mist system, or a compliant secondary escape, is designed in. We build the fire strategy into the drawings from the outset rather than leaving building control to reshape it late.
A converted roof needs new structure. Typically that means steel beams spanning the house onto the existing walls, with alterations to the ridge, purlins and rafters that a structural engineer designs and calculates. On the Suburb's many semi-detached and terraced cottages those beams usually bear into the party walls, engaging the Party Wall etc. Act 1996, so notices go to the neighbours on either side before work begins. The conversion is also the moment to upgrade the roof's insulation to current standards — carefully, so that a steep, historic roof is not spoilt by clumsy build-ups or vents pushed through a prominent, visible slope.
In the Suburb the deciding question is how the new roof reads. The Arts-and-Crafts roofscape — steep pitches, gables, chimneys and carefully placed original dormers — is a designed skyline, and additions are judged against it from the street, the greens and neighbouring gardens. A rear dormer is generally kept subordinate, set down from the ridge and in from the sides, and slated or tiled to match; anything on a front or street-facing slope is far harder to justify. Because an Article 4 direction and the Trust's scheme both bite here, we design the roofscape to the specific street and set out the case in the drawings.
