Loft Conversion Cost per m² UK

Average Loft Conversion Cost per m²

Costs exclude the staircase if a new one is required — typically £3,500–£7,500 on top.

Why Cost per m² Is Misleading

A smaller loft conversion will always cost more per m² than a larger one. That's because many costs are fixed:

• Staircase — costs roughly the same whether the loft is 15 m² or 50 m².
• Building Regulations compliance — fire safety, ventilation and structural works are largely fixed costs regardless of size.
• Plumbing and electrics first fix — similar cost whether you're adding one room or two.
• Party wall agreements — a terraced house neighbour agreement costs the same no matter the size.

What Drives Cost Per m² Up or Down

• Number of dormer windows — each dormer adds structural steel, windows and flashing
• Specification level — en-suite bathroom, high-end finishes, underfloor heating all add cost
• Site access — if the house is mid-terrace with no rear access, materials must come through the house — harder and slower
• Roof complexity — multiple roof angles, valleys and junctions add structural and roofing cost
• Heritage or conservation area — additional requirements for matching materials

Regional Differences

London is consistently the most expensive region — typically 35–45% above the UK national average for loft conversions. The North East and Scotland tend to be the most affordable. These differences are primarily in labour rates, not materials.