Loft Conversion Company in London

Dormer Loft Conversions

The most common conversion in London, and the most adaptable.

A dormer extends the roofline vertically at the rear, side, or both, adding full head height and usable floor space across most of the loft. In most cases it falls under permitted development rather than requiring a full planning application, which makes it the fastest route to extra space for the majority of London's terraced and semi-detached housing stock.

Hip-to-Gable Loft Conversions

Squaring off a hipped roof to add usable width.

Where a property has a hipped roof rather than a gabled one, converting the sloped side into a vertical gable wall adds meaningful floor space before any dormer is even considered. Common across much of outer London's 1930s semi-detached stock, and frequently combined with a rear dormer where clients want maximum headroom across the full loft.

Mansard Loft Conversions

The most substantial conversion, and the most planning-sensitive.

A mansard reconstructs the rear roof slope to a near-vertical angle, delivering the greatest possible headroom and floor area of any loft conversion type. It almost always requires full planning permission rather than permitted development, particularly across London's conservation areas, and is the configuration best suited to a genuine full additional storey rather than an incremental extension.

Cost by Conversion Type

A simple rooflight conversion, where no dormer or structural roof alteration is needed, starts from around £40,000. Beyond that:

• Dormer loft conversion: £55,000–£90,000 — the most common type in London
• Hip-to-gable loft conversion: £60,000–£95,000
• Mansard loft conversion: £100,000–£175,000+ — the premium option and typically the one requiring full planning permission

For an indicative figure against your own property, use the cost calculator.

What Drives the Price at the Luxury End

Within each configuration, the range is set by structural complexity, glazing specification and finish. A steel structural spine, full-height glazing to a rear dormer, bespoke joinery to the new floor, and integrated climate or smart-home systems all move a project toward the top of its range. At Sovran, every quote is fixed before work starts, so the number agreed at contract stage is the number paid at handover, not a starting estimate that grows with the build.

Permitted Development Rights for Lofts

Permitted development allows most rear dormer conversions up to a defined volume without a full planning application, though the allowance is smaller for terraced houses than for detached and semi-detached properties, and is removed entirely on designated land such as conservation areas and some Article 4 directions, which cover large parts of inner London. Mansard conversions, and any conversion that alters the roof at the front of the property, require full planning in almost every case.

The Party Wall Act and Your Neighbours

Most London loft conversions involve work directly on or near a shared wall, which brings the Party Wall Act 1996 into play regardless of whether planning permission is required. Sovran manages the full party wall process, from serving notice through to agreeing the award with the adjoining owner's surveyor, so it runs alongside the design and planning programme rather than delaying it.

One detail worth knowing early: under Approved Document B, converting a two-storey house into a three-storey dwelling triggers a protected staircase requirement, with fire doors at every level. Sovran builds this into the design from the first drawing, so it never becomes a late surprise in the programme.