How long does a loft conversion take, step by step?

Most loft conversions in Cambridge take between 8 and 10 weeks on site, plus roughly 6 to 10 weeks beforehand for design, drawings and approvals. A rooflight conversion is at the quicker end, while a dormer or mansard sits at the longer end because of the extra structural work. Here is what happens, week by week.

When people ask how long a loft conversion in Cambridge takes, they usually mean the building work. That is the 8 to 10 weeks below. It is worth remembering that a well-run project also has a design and approvals stage first, and getting that right is what keeps the build on schedule.

Before work starts: design and approvals

The design stage comes first: a measured survey, architectural drawings, a structural engineer, and any planning application or building-regulation approvals. This typically takes around 6 to 10 weeks, and most of that is waiting on approvals rather than active work. If your project falls under permitted development it can be at the quicker end. In a conservation area, where a full planning application is needed, allow longer.

Weeks 1 to 2: structure

Scaffolding goes up, the roof is opened where needed, steel beams are installed and the new floor is strengthened and laid. This is the noisiest and most disruptive stage, but it is also the fastest to show progress. By the end of it the shape of the new room is clear.

Weeks 3 to 4: roof and weatherproofing

The dormer or roof alterations are built and the loft is made watertight, so the rest of the work can continue inside whatever the weather. This is the point where a dormer or mansard takes longer than a rooflight conversion, because there is more roof to build.

Weeks 5 to 6: windows, insulation and first fix

Windows and rooflights go in, the space is insulated to current standards, and first-fix electrics and plumbing are run through the walls and floor. The new staircase is usually fitted at this stage, which is often the moment the conversion starts to feel like part of the house rather than a building site.

Weeks 7 to 8: plastering and second fix

Walls and ceilings are plastered, then second-fix electrics and plumbing are completed, along with any en-suite bathroom. Radiators, sockets, switches and light fittings go in, and the room is ready for decoration.

Weeks 9 to 10: finishing and handover

Decorating, flooring, doors and final fittings are completed, the work is snagged, building control carries out the final inspection and signs off, and we hand over a finished room ready to use. You receive the building-regulation completion certificate, which you will need if you ever sell or remortgage.

What can affect the timeline

Several things can shift the dates: planning permission and party wall agreements, the type of conversion, the age and condition of the roof, and the weather during the opening-up stage. Older Cambridge properties sometimes reveal surprises once the roof is opened, which is why a good survey up front matters. We give you a written programme with the key stages and dates before we start, and we keep you updated throughout the build.

How to prepare your home

A little preparation makes the build run more smoothly. Before we start, it helps to clear the loft completely and to move anything precious or fragile away from the landing and top-floor rooms, because there will be traffic up and down the stairs while the new staircase is being formed. We protect floors and stair runs, seal the work area with dust sheeting and set up the scaffolding to keep foot traffic outside where possible. Parking matters too: on many Cambridge terraced streets, arranging a skip permit and a space for deliveries in advance avoids delays once the job is under way. We handle the site logistics, but knowing the rhythm of the work, noisy at the start, calmer once the roof is closed in, helps you plan around it. If you work from home, the quieter later weeks are a good time for important calls.

Living in the house during the work

Most clients stay in their home throughout. The dust and noise are concentrated in the first couple of weeks, and because the loft is sealed off from the rest of the house the disruption is manageable. For more on planning your project, see our guides on cost, planning permission and the value it adds.