The Typical Loft Conversion Journey
A standard loft conversion in London — typically a dormer or hip-to-gable — takes between 8 and 16 weeks on site once work begins. The full project, from first site visit to completion, usually spans 4 to 7 months when design and approvals are included.
This guide breaks down the key stages.
Stage 1: Design and Pre-Construction (4–12 Weeks)
Before any site work begins, the following needs to happen:
Weeks 1–2: Initial assessment and feasibility
- Site visit to assess head height, roof structure, and access options
- Architectural brief agreed
- Concept drawings produced
Weeks 3–5: Design development
- Planning drawings prepared
- Structural engineer engaged for initial input
- Building Regulations pre-application discussions if needed
Weeks 5–8: Approvals
- Planning application submitted if required (8-week statutory determination period)
- Building Regulations application submitted (full plans route preferred)
- Party Wall Notices served if applicable (minimum 2 months' notice)
For permitted development loft conversions, the planning stage may be skipped, reducing pre-construction time significantly.
Stage 2: Procurement and Pre-Start (2–4 Weeks)
Once approvals are in place:
- Detailed specification agreed
- Materials and specialist components ordered (steel beams, roof windows, structural timber)
- Scaffold erected and site set up
- Pre-start meeting with client
Stage 3: Structural and Roof Works (Weeks 1–4 on Site)
- Floor structure installed (new structural floor joists or engineered floor system)
- Dormer or hip-to-gable structure built
- Roof windows and dormer cheeks installed
- Roof made weathertight
- Steel beams installed if structural openings required below
This phase is weather-dependent. Wet or icy conditions slow exterior works.
Stage 4: First-Fix Works (Weeks 4–7)
- Insulation installed to roof and walls
- First-fix electrics run (lighting, sockets, smoke detectors)
- First-fix plumbing run if bathroom is included
- Staircase structure installed
- Internal stud partitions built
Stage 5: Boarding and Plastering (Weeks 7–9)
- Plasterboard fixed to walls and ceiling
- Wet plaster or skim applied
- Plaster allowed to dry (minimum 2 weeks before decoration)
Stage 6: Second-Fix and Finishing (Weeks 9–13)
- Second-fix electrics (sockets, switches, lighting pendants)
- Second-fix plumbing (bathroom suite, radiators, towel rails)
- Joinery (skirting, architrave, doors, door frames, window boards)
- Staircase completed with handrail and balustrade
- Decoration (client-supplied or contractor)
- Flooring (client-supplied and installed)
- Bathroom tiling and finishing
Stage 7: Completion and Sign-Off
- Building Control inspection and completion certificate
- Snagging list raised and resolved
- Handover to client
Total Timeline Summary
| Route | Pre-Construction | On Site | Total |
|---|---|---|---|
| Permitted Development | 6–8 weeks | 8–12 weeks | 3–5 months |
| With Planning Permission | 14–20 weeks | 8–12 weeks | 5–8 months |
| Complex conversion | 16–24 weeks | 12–16 weeks | 7–10 months |
Common Causes of Delay
- Late approval of structural engineer drawings
- Party wall disputes or delayed neighbour agreements
- Changes to design after work has started
- Materials delays (especially specialist roof windows)
- Weather during roof opening phase
RCB Design & Build
RCB produces a clear programme at the pre-construction stage so clients know exactly what to expect at each phase. We coordinate planning, Building Control, structural input, and procurement before the first day on site — reducing the risk of delays and keeping the project on track.