Renovations & Extensions · 2025-09-12 · 8 min read
Loft Conversion Cost London 2025: Full Price Guide
A genuine 2025 price breakdown for Velux, dormer, hip-to-gable and mansard loft conversions across London · with planning, timeline and cost-driver detail.
Real London loft conversion prices for 2025. Velux from £18k, dormer from £28k, mansard from £45k. Planning permission, timeline and what affects cost.
What this guide covers
Written for London landlords, agents and homeowners by working tradespeople. We cover the up-to-date 2025 pricing, legal duties (where they apply), the common pitfalls our engineers see weekly and the practical steps to take next. No content-marketing fluff — just the numbers, the obligations and the order of operations.
Why Renovations & Extensions matters in London right now
Renovations & Extensions in London moves fast — costs rise, legislation tightens, expectations shift. The advice below reflects what we are quoting, fitting and certifying this month across all 33 boroughs and the M25 commuter belt. Specific borough pricing variations are noted in our area guides.
How Local Property Group can help
- Free site survey (photo-based or in-person within the M25)
- Fixed-price quote itemised by labour and parts, held for 14 days
- Certified trades — Gas Safe, NICEIC, PCA, BDMA, FMB, TrustMark
- Public liability insurance up to £5M, written 1-year labour guarantee
- Single point of contact from quote through to certificate
Related service: Loft Conversions service — get a free fixed-price quote.
Read more on the Local Property Group blog or browse our cost guides for benchmark prices on every common London property job.