How Long Does a Loft Conversion Take? A Realistic Timeline

One of the most common questions we're asked, alongside costs, is how long the whole process takes. And like costs, the honest answer is: it depends. But we can give you a realistic framework — and flag the things that can add time — so you can plan properly.

The total time from first conversation to moving into your new room is typically anywhere from 14 to 24 weeks. That might sound like a wide range, but the variation is genuine and depends on whether you need planning permission, how quickly drawings are prepared, and how complex your particular conversion is.

Phase 1: Design and Technical Drawings (2–4 Weeks)

Once you've agreed to go ahead, the first step is producing measured drawings of your existing loft space and the proposed conversion. We work with experienced local architectural technicians who understand the specific requirements for Building Regulations submissions in West Sussex.

For a straightforward Velux or dormer conversion that falls within Permitted Development, this phase is about getting the technical drawings right for Building Control rather than navigating planning committees. The drawings will cover structural details, roof construction, insulation specification, means of escape, and staircase design. Typically this phase takes two to four weeks from instruction.

If your conversion requires bespoke structural solutions — large steel beams, for instance, or an unusual roof configuration — your structural engineer will also need to provide calculations at this stage.

Phase 2: Planning (6–8 Weeks if Required)

If your conversion falls within Permitted Development, this phase doesn't apply to the planning process, but we still recommend applying for a Lawful Development Certificate (LDC), which takes around four to six weeks to be issued by Adur & Worthing Councils.

If full planning permission is required — for a mansard, for a property in a conservation area, or for a conversion exceeding PD limits — you should budget for the statutory eight-week determination period, which can run longer if the council requests additional information or if there are objections to deal with.

Building Regulations approval can run alongside planning in most cases. Adur & Worthing Building Control typically take two to three weeks to issue a decision on a Full Plans application, after which the build can proceed with site inspections at key stages.

Phase 3: The Build (6–10 Weeks)

This is where your loft conversion actually happens. For a typical dormer conversion — the most common type in Worthing — the build phase breaks down roughly as follows.

Weeks one and two cover the structural and roofing work: scaffolding erection, opening up the roof, installing the structural steels or timber structure, building the dormer shell, and making the roof weathertight. This is the most visible and dramatic phase, and it's also where the noise and activity are greatest.

Weeks three and four move to first fix: flooring structure, staircase installation, windows fitted, and the first fix of electrics and plumbing (if an en suite is included).

Weeks five to seven cover insulation, plasterboarding and plastering — at which point the new space starts to look like a room for the first time.

Weeks eight to ten are the second fix and finishing phase: skirting boards, door linings, floor coverings, bathroom fitting, lighting, decoration. The Building Control sign-off visit and final snagging happens at the end of this phase.

Factors That Can Affect the Timeline

Several things can add time to a project. Adverse weather during the roofing phase — particularly prolonged rain in autumn and winter — can slow exterior works. Material delays, though less common than during the supply chain disruptions of a few years ago, can still occur for specialist items like bespoke roof lanterns or particular timber species. Any unforeseen structural issues discovered once the roof is opened also need to be resolved before work can continue.

On the flip side, projects move faster when decisions are made promptly. Choosing your finishes — floor coverings, bathroom tiles, sanitary ware — before the build starts means the second fix team aren't waiting on deliveries. We'll always give you a specification checklist early on to help with this.

Can You Live at Home During the Work?

In almost all cases, yes. Loft conversions are carried out above the existing occupied house, and we take care to seal off the stairwell and keep the work area separate from your living space. Dust sheeting and careful site management are part of how we work. The noisiest phases — structural steelwork and breaking through for the staircase opening — are typically brief and we'll always give you advance notice.

The staircase installation is the one moment of genuine disruption, as it requires a temporary hole in your first floor ceiling to create the new opening. We manage this carefully and close it up quickly. If you have young children or a particular sensitivity to dust and noise, it's worth planning ahead for those peak phases — but most families find the experience much less disruptive than they'd feared.