Loft conversions cost
This page explains what drives loft conversions costs and gives you an estimated range from the same questions a contractor would ask. It is an estimate, not a quotation — the actual price depends on site-specific factors.
Last updated 22 Sept 2026
What loft conversions work involves
A loft conversion turns roof space into habitable rooms. The feasible type — rooflight, dormer, hip-to-gable or mansard — is decided by the available head height and the roof structure, not by preference alone.
Loft conversion costs depend on roof structure, dormers and staircase position.
Estimate your loft conversions cost
Most loft conversions projects we hold cost data for fall between £30,000 and £55,000. Dormer, 1 bedroom
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Estimated range only. The actual price depends on site-specific factors such as access, condition and specification.
What changes the price
- Conversion type
- Rooflight conversions are the simplest; dormer, hip-to-gable and mansard each add structural work.
- Head height and structure
- Trussed roofs need more structural intervention than a traditional cut roof.
- Staircase position
- Fitting a compliant stair often means remodelling the floor below.
- Bathroom
- An en suite adds drainage, ventilation and waterproofing.
- Insulation, fire and escape
- Fire doors, protected escape routes and insulation upgrades are regulatory requirements, not extras.
What a contractor will ask about your property
- What is the height from the ceiling joists to the ridge?
- Is the roof trussed or a traditional cut roof?
- Where could the staircase go?
- Do you want a bathroom in the loft?
- Is the property terraced, semi-detached or detached?
How a project usually runs
- 1
Feasibility
Head height measured, roof structure and stair position assessed.
- 2
Design and approvals
Drawings, structural design, planning where needed, building regulations.
- 3
Structure
Steels, new floor, dormer or roof alterations.
- 4
Fit out
Stair, insulation, plastering, bathroom, fire protection and decoration.
Permissions and regulations
- Many conversions are permitted development, but dormers and mansards frequently need planning permission.
- Building regulations cover structure, fire escape, insulation and stairs.
- Party wall agreements are common in terraced and semi-detached properties.
Problems that commonly come up
- Insufficient head height for a compliant conversion.
- Water tanks, soil vents and chimney breasts in the way.
- No viable staircase position without losing a bedroom below.
When you need a specialist
- A structural engineer is required for the new floor and any roof alterations.
- Fire safety detailing should be designed, not improvised.
Related services
Common questions
Is my loft tall enough?
Measure from the top of the ceiling joists to the underside of the ridge. If it is marginal, the conversion type and the finished ceiling height become the deciding factors.
Will I need planning permission?
Rooflight conversions often do not; dormers and mansards often do. It depends on size, position and the property.
Is the estimate a quotation?
No. Loft feasibility needs a survey; the estimate is an indicative range.
Get quotes for your project
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