Loft Conversion Cost Calculator UK
Get a 2026 UK loft conversion estimate in 30 seconds. Choose loft type, size, finish level and region for an instant low/mid/high figure — Velux, dormer, hip-to-gable and mansard pricing at specialist rates, structural work incl. VAT. No email required.
Estimate Your Loft Conversion Cost
4 steps. Supply-and-fit including structural work, insulation, staircase, dormer/Velux windows, plaster, decoration, electrics and VAT.
How This Calculator Works
Our loft conversion calculator combines four inputs (loft type, floor area, finish level and region) with 2026 UK supply-and-fit rates from specialists across our 519-town database.
Two things routinely move a real quote away from the mid estimate above, and neither is captured by floor area alone. The first is the staircase: building regulations usually demand a compliant stair rising into the new floor with proper headroom, and if there is nowhere sensible for it to land you lose a slice of a bedroom below. The second is the head height under the existing ridge, which decides whether a cheaper Velux scheme is even possible or whether you are forced into a dormer. For a wider sense-check on the numbers, the average cost of a loft conversion in 2026 sets typical spend by house type, while the loft conversion cost by type table breaks the per-m² rates down by Velux, dormer, hip-to-gable and mansard.
Base Shell Rates (per m²)
- Velux only — £1,200/m²
- Dormer — £1,800/m² (UK's most popular)
- L-shaped dormer — £2,300/m²
- Hip-to-gable — £2,100/m²
- Mansard — £2,500/m² (maximum space)
Includes structural steelwork, floor joists, roof modifications, insulation (Part L 2022), staircase, plastering, standard finishes, electrics (Part P certified) and heating extension.
Finish & Regional Multipliers
- Basic 0.85× · Standard 1.00× · Premium 1.35× · Luxury 1.70×
- London 1.28× · South East 1.14× · South West 1.05×
- East of England 1.08× · Midlands 1.00× (baseline)
- North West 0.93× · North / Yorkshire 0.92×
- Wales 0.94× · Scotland 0.96× · NI 0.88×
Low/high band is ±15% around the mid estimate to reflect real market spread. A firm price follows a home survey and structural design.
Typical Loft Conversion Costs (2026)
Standard-finish supply & fit by loft type and typical floor area, Midlands baseline (±15% band).
| Loft type & size (standard finish) | Mid estimate | Cost range (fitted) |
|---|---|---|
| Velux / rooflight, 18 m² (Midlands) | £21,600 | £18,400–£24,800 |
| Dormer, 22 m² (Midlands) | £39,600 | £33,700–£45,500 |
| Hip-to-gable, 26 m² (Midlands) | £54,600 | £46,400–£62,800 |
| L-shaped dormer, 30 m² (Midlands) | £69,000 | £58,700–£79,400 |
| Mansard, 35 m² (London, premium finish) | £151,200 | £128,500–£173,900 |
These figures power the calculator above — enter your own spec for a tailored estimate. For the full breakdown, read our complete loft conversion cost guide.
Frequently Asked Questions
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