Dormer, hip-to-gable and rooflight loft conversions
Loft Conversions
A loft conversion converts an existing roof void into usable living space — typically a bedroom with en-suite — by adding a dormer or rooflights, strengthening the floor, forming a staircase and meeting Building Regulations for insulation, structure and fire escape.
Definition
What Loft Conversions covers
A loft conversion brings the roof space of an existing house into habitable use. Depending on the roof form and available head height, this may be achieved with rooflights alone, a rear or side dormer, a hip-to-gable extension, or a full mansard, and requires a new or reinforced floor structure, staircase access, insulation and a means of escape in case of fire.
Suitable for
- Houses with roof head height suitable for conversion (usually assessed at survey)
- Households wanting an extra bedroom, bathroom or home office without extending the footprint
- Terraced, semi-detached and detached houses with a traditional cut or trussed roof
- Owners planning a dormer or rooflight conversion with an en-suite
Not suitable for
- Roofs with insufficient head height where survey shows no workable layout can be achieved
- Flats and leasehold properties without freeholder consent to alter the roof
Process
How the work is carried out
- 01
Feasibility survey
Checking head height, roof structure, joist span and existing services to confirm what form of conversion the roof will support.
- 02
Design and approvals
Preparing drawings, agreeing whether the scheme falls under permitted development or needs a planning application, and submitting Building Regulations.
- 03
Structural works
Strengthening the floor, forming the dormer or roof alterations, installing the staircase and structural steel where required.
- 04
Fit-out and completion
Insulation, first and second fix services, plastering, joinery and decoration, finishing with Building Control sign-off.
Typical timescale
A loft conversion typically takes six to ten weeks on site once design and approvals are settled, though dormer and mansard conversions with more structural work can take longer. Confirmed in your project programme after survey.
Cost guidance
Loft conversions typically cost £25,000–£60,000 per job in our area, with a dormer or rooflight design and the addition of an en-suite driving the range toward the top end. We provide an itemised quotation after a feasibility survey rather than a fixed headline price.
Limitations and exclusions
- Dormer and roof alterations may need planning permission depending on size, position, and whether permitted development rights apply to the property
- A protected escape route or suitable fire escape window is required by Building Regulations and may affect the layout
- Existing roof structure condition is confirmed once opened up and may require further remedial work
Areas we cover
Loft Conversions across Sussex, Surrey, Kent and South London
Local property styles, planning authorities and neighbourhood coverage for loft conversions in each town we work in.
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FAQs
Loft Conversions FAQs
Do I need planning permission for a loft conversion?
Many loft conversions fall under permitted development if the added roof volume stays within set limits (typically 40m³ for terraced houses, 50m³ for semi-detached and detached) and materials match the existing house. Conversions on designated land, in conservation areas, or exceeding those limits need a full planning application, which we confirm at survey.
How much head height do I need for a loft conversion?
As a general guide, at least 2.2–2.3m from the top of the ceiling joist to the underside of the ridge gives a workable conversion, though this varies with roof pitch and the design chosen. We measure this precisely during the feasibility survey.
Will I need a party wall agreement for my loft conversion?
If the conversion involves work to a wall shared with a neighbour — a hip-to-gable extension is a common example — the Party Wall etc. Act 1996 will usually require notice to be served before work starts. We flag this during design.
Discuss your loft conversions project
Tell us about the property and what you have in mind, and we'll arrange a site visit.
Last reviewed 2026-07-28.