Builder stages for your loft conversion project
Please note that these are rough guides only. To get a clear cost breakdown of each stage for your loft conversion project, please post your project and get up to 5 free quotes
Loft Conversion Project
(Turning your unused loft into a bright, compliant new living space)
Once planning permission and structural drawings are approved, your builder begins the on-site transformation — converting your attic into a safe, comfortable, and beautifully finished new room.
Pre-Start & Preparation
Contract confirmation and site preparation
Site Setup & Safety
Scaffolding and protection installation
Strip-Out & Structural Preparation
Clearing the loft and preparing for structural changes
Structural Works (Steels, Floor & Roof)
Building the new structure
Roof Works & Weatherproofing
Making the loft weather-tight
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Builder step-by-step cost guide for your loft conversion project.
(Please note that these are rough guides only; to get an loft conversion cost breakdown of each stage, please post your project and get up to 5 free quotes.)
Builder Cost Breakdown – Typical Loft Conversion Project
All figures are rough guides only and vary by location, design complexity, and specification. Based on 2025 averages, excluding VAT.
Typical overall cost: £1,800 – £2,800+ per m²
Example: 30 m² loft conversion ≈ £54,000 – £84,000
Pre-Start & Site Setup
2–4%
Approx. cost: £1,000 – £3,000
Structural Preparation & Steelwork
10–15%
Approx. cost: £6,000 – £12,000
Roof Alterations & External Works
15–20%
Approx. cost: £8,000 – £16,000+
Windows, Insulation & Boarding
8–10%
Approx. cost: £4,000 – £8,000
First Fix Services (Mechanical, Electrical & Plumbing)
8–10%
Approx. cost: £4,000 – £8,000
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