Published 25 April 2026 · Updated 14 May 2026
By Jon Thompson, Director — Living Design & Build Ltd, FMB-member builder, Bridgnorth
Online answers to 'how long does an extension take' usually quote optimistic numbers that assume nothing goes wrong. After 1,000+ projects across Shropshire and the West Midlands, here are the timelines we actually program.
Single-storey rear extension (25m²)
- Weeks 1–2: Strip out, foundations, drainage
- Weeks 3–4: Brickwork to wall plate
- Weeks 5–6: Roof structure, weatherproof
- Weeks 7–8: Windows and doors installed
- Weeks 9–10: First-fix electrics and plumbing, plastering
- Weeks 11–12: Kitchen install, second-fix, flooring
- Weeks 13–14: Decoration, snagging, handover
Realistic total: 12–16 weeks. Add 2 weeks if the kitchen has long lead-times.
Two-storey extension (50m² total)
- Weeks 1–3: Foundations, drainage, ground floor brickwork
- Weeks 4–7: First floor brickwork, roof structure
- Weeks 8–9: Roof tiling, windows installed, scaffold down
- Weeks 10–13: First-fix services, plastering, screeding
- Weeks 14–17: Bathroom and kitchen installs, second-fix
- Weeks 18–20: Decoration, flooring, snagging
Realistic total: 16–22 weeks.
Wrap-around extension
Wrap-around extensions take longer than a simple single-storey of the same area because of the extra structural openings between old and new, more complex roof junctions, and usually a full ground-floor reorganisation.
Realistic total: 18–24 weeks.
Before site start
Most clients underestimate the pre-build phase. From first site visit to spades in the ground is usually 12–20 weeks:
- Site survey and design: 2–3 weeks
- Planning application or permitted development confirmation: 8 weeks
- Structural calculations and Building Regulations: 3–4 weeks (often runs parallel)
- Quote, contract and material ordering: 2–3 weeks
- Slot in our schedule: 2–8 weeks depending on time of year
Frequently asked questions
What's the best time of year to start?+
Spring (April–May) is ideal — you get dry weather for the groundworks and roof, and finish in time for autumn. October–November starts work too, but groundworks in heavy rain can add a week. Avoid mid-December starts; trades are scarce after Christmas.
Can the build run faster if I pay more?+
Generally no. Most build steps are sequential — you can't plaster before first-fix is done, you can't tile before plaster has dried. More money buys nicer finishes, not faster timelines.