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Convert your loft.
Velux, dormer, hip-to-gable or mansard — full process, costs and timelines for a UK loft conversion.
✓ Updated May 2026✓ Free quotes✓ Vetted pros
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Costs, timelines, pitfalls and the right questions to ask before any loft conversions starts on loft Conversion.
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Hiring a loft conversions, without the regret.
Four moves that separate a smooth job from a nightmare.
Inadequate headroom
Loft needs 2.2m+ headroom over 50% of usable area. Some lofts need raising.
Cheap stairs
Spiral or alternating-tread to save space — non-compliant Part K.
Fire-rated doors missed
All doors to escape stair must be FD30. Cheap conversions skip this.
Cold bridging
Insulation must be continuous. Cheap installs leave thermal bridge.
Costs & timeline
Know what it costs. Know when it ends.
Indicative UK ranges and a typical week-by-week schedule.
Cost range
By job type
Inc. VAT · 2026
Source: NMT quotes
Source: NMT quotes
Velux-only conversion (small)No dormer
£30k–£45k
Rear dormer conversion (medium)Most popular UK
£40k–£65k
Hip-to-gable conversion (larger space)End-terrace properties
£50k–£80k
Mansard conversion (max space)Premium urban
£60k–£110k
L-shape dormer (Victorian terrace)Common London
£55k–£95k
En-suite bathroom additionPlus plumbing
£4.5k–£12k
!
Quote spread is typically ± 18% — always get 3 quotes.
Timeline
Dormer loft conversion · week by week
Typical
6 phases · 10 wk
6 phases · 10 wk
W1
W2
W3
W4
W5
W6
W7
W8
W9
W10
Structural + design
Strip + steels in
Dormer build + roof
1st + 2nd fix
Plaster + finishes
Snags + handover
!
Schedule slips on dependencies — pad each phase by 10–20% for real-world delays.
At a glance
Infographic · VideoThe Loft Conversions briefing.
Infographic
Loft Conversions quick-view
Video guide
Loft Conversions explained
A loft conversion is one of the highest-ROI home improvements in the UK — adds 15-25% to property value, creates a usable room without losing garden space. Expect to pay £30,000–£80,000 for UK loft conversion depending on type and complexity.
What Does the Work Involve?
Architect designs conversion. Structural calculations. Building Regs application. Construction: new floor joists (often double up existing), structural support steel for chimney breast, dormer or roof window construction, stairs to loft (Part K compliant), insulation, plumbing if en-suite, electrical first fix, plastering, finishes, decoration.
Typical Costs
| Item | Low (£) | High (£) | Notes |
|---|---|---|---|
| Velux-only conversion (small) | 30,000 | 45,000 | No dormer |
| Rear dormer conversion (medium) | 40,000 | 65,000 | Most popular UK |
| Hip-to-gable conversion (larger space) | 50,000 | 80,000 | End-terrace properties |
| Mansard conversion (max space) | 60,000 | 110,000 | Premium urban |
| L-shape dormer (Victorian terrace) | 55,000 | 95,000 | Common London |
| En-suite bathroom addition | 4,500 | 12,000 | Plus plumbing |
| Architect + structural engineer | 2,500 | 8,000 | 10% of build cost |
How Long Does It Take?
Design and approvals: 8-16 weeks. Construction: 10-16 weeks. Total project: 18-32 weeks (4-8 months).
DIY or Professional?
Professional only. Building Regs notification mandatory. Multi-trade coordination required.
Choosing the Right Tradesperson
Specialist loft conversion company (Econoloft, Simply Loft, Granit) or general builder with verifiable previous conversions. Architect for design. Structural engineer for calcs. FMB or NFB membership.
UK Regulations
Full Building Regs notification: Part A (structure), Part B (escape — fire-rated doors and protected stair), Part L (thermal), Part K (stair), Part F (ventilation), Part P (electrical). Often planning permission for rear dormer; Lawful Development Certificate for Velux-only. Listed buildings need consent.
Common Problems
- Inadequate headroom: Loft needs 2.2m+ headroom over 50% of usable area. Some lofts need raising.
- Cheap stairs: Spiral or alternating-tread to save space — non-compliant Part K.
- Fire-rated doors missed: All doors to escape stair must be FD30. Cheap conversions skip this.
- Cold bridging: Insulation must be continuous. Cheap installs leave thermal bridge.
Frequently Asked Questions
Will my loft convert?
Need 2.2m+ headroom over 50% of usable area (Part K). Most pre-1965 UK roofs convert; some shallow-pitch modern lofts need raised roof (£15,000+ extra).
Velux or dormer?
Velux only: cheapest (£30,000-£45,000), less space, often permitted development. Dormer: more space and headroom, more cost (£40,000-£65,000), often needs planning.
How much value does it add?
Quality conversion: 15-25% to property value. ROI typically 100-150% on build cost in growth markets.
Can I have en-suite?
Yes — popular addition. Adds £4,500-£12,000 to project. Plumbing runs from existing bathroom.
How long does the build take?
10-16 weeks construction. Plus 8-16 weeks design and approvals. Total 4-8 months.
Loft specialist or general builder?
Specialist: faster, experienced. General builder: cheaper, may be slower. Specialist often better value despite slight cost premium.
This guide was written with AI assistance and is intended for general information only. Prices are estimates based on UK averages and may vary by region. Always get at least three quotes and consult a qualified professional before starting any work.
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