Loft Conversion in London

Rooflight & Velux Conversions

The simplest and most budget-friendly loft conversion type, adding rooflights into the existing roof slope without altering the roof's shape. Because the structure isn't being changed, this usually falls under permitted development rather than needing full planning permission, and it's the fastest conversion type to complete.

The trade-off is headroom — a rooflight conversion doesn't add the extra height a dormer or mansard does, so it only works well where the existing roof pitch already gives enough head height to stand comfortably across most of the new room.

Dormer Conversions

The most common loft conversion type in London, a dormer extends vertically from the existing roof slope, adding both headroom and usable floor space rather than just light. A rear dormer is often achievable under permitted development, provided it stays within specific size and position limits, while a front-facing dormer more often needs full planning permission.

Dormers suit most standard pitched roofs and are the default choice for a family wanting a genuinely usable extra room — a proper bedroom or office — rather than just additional light and modest headroom.

Hip-to-Gable Conversions

A hip-to-gable conversion extends a hipped roof end out to a vertical gable wall, significantly increasing usable floor area on that side of the loft — genuinely valuable on semi-detached and detached properties, where a hipped roof end would otherwise waste meaningful potential space. This almost always needs full planning permission, since it changes the roof's shape rather than adding a smaller feature within the existing structure.

It's often combined with a rear dormer on the same project, since the two changes complement each other structurally.

Mansard Conversions

The most involved loft conversion type, a mansard replaces one or both roof slopes with a near-vertical wall and a shallow-pitched roof on top, maximising usable space more than any other conversion type. It's particularly common on London terraces, where a rear mansard can add a genuinely full extra storey's worth of usable space rather than a partial one.

Almost every mansard conversion needs full planning permission, and it's the most structurally involved option — a longer timeline and higher cost in exchange for the most substantial space gain available from a loft.

Building Regulations & Structural Requirements

Every loft conversion, regardless of type, needs building regulations approval separate from planning permission — structural calculations for the new floor, insulation standards, and fire safety requirements all get checked and signed off by building control, not just designed and hoped for. The existing roof structure and ceiling joists almost always need strengthening to support a genuine floor, one of the less visible but more expensive parts of any loft conversion, and something that gets accounted for in the quote from the outset rather than discovered once work's already begun.

Staircase Access & Fire Safety

Getting a staircase into a loft conversion, without losing too much space from the floor below, is a genuine design constraint on most projects — the staircase position affects the layout of both the loft and the room beneath it, and it's usually decided earlier in the design process than people expect, since it constrains almost everything else about the layout. Fire safety requirements shape the design too: an escape route from the new loft room, often via a protected stairway or fire doors on the floors below, is a building regulations requirement, not an optional extra.