Written by the Loft Life team, who have project-managed loft conversions across London and Kent for more than 25 years. Last updated 25 June 2026. Read time: ~8 minutes.

How long does a loft conversion take? Most take six to eight weeks of on-site building work. A simple Velux conversion can be finished in three to five weeks, while a larger dormer or L-shape runs to eight to twelve weeks. On top of the build, allow two to four weeks beforehand for design, drawings and approvals. The timings below show exactly what happens and when.

Do You Have to Move Out During a Loft Conversion?

No, almost everyone stays in their home throughout. For most of the build, the work happens up in the roof and is reached from an external scaffold, so your day to day living’s barely touched. The loft is only opened up to the rest of the house near the end, when the new staircase goes in. There’s some dust and noise on the busier days, but you keep your kitchen, bathroom and bedrooms in use the whole time.

What Happens Before the Build Starts

The build time is the on-site phase only, and the weeks on site are just part of the story. Before a single tile comes off, there’s a design and approvals stage that usually runs two to four weeks. This is where the drawings are produced, the structural calculations are worked out, and the building control application goes in. If your conversion needs planning permission, that step sits here too, and it’s the one that can stretch the front of the project.

How Long Each Type of Loft Conversion Takes

The conversion type is the biggest factor in the timeline. A Velux conversion keeps the existing roof shape and simply adds roof windows, so it’s the quickest at three to five weeks. A dormer or hip to gable involves building out the roof to create extra space and headroom, which takes six to eight weeks. An L-shaped conversion joins two dormers across a period property and is the largest job, so it sits at eight to twelve weeks. Your survey gives you a firm timeline for your specific property.

A Week-by-Week Loft Conversion Timeline

Here’s how a typical dormer conversion runs from the first day on site to handover. Smaller jobs compress this, larger ones extend it, but the order of work stays the same.

By the end of week four your loft’s sealed against the weather, which is the point where the project feels like it’s turned a corner. The second half of the build is where the empty shell becomes a finished room.

Why an In-House Team Keeps Your Loft Conversion on Schedule

The single biggest cause of delays on a loft conversion isn’t the building work. It’s the gaps between trades. When a separate builder, electrician, plasterer and joiner each turn up when they can fit you in, a job that should take eight weeks drifts to twelve or more while everyone waits on someone else.

We run the trades as one team, so the plasterer knows the day the first fix finishes, and the joiner knows the day the plastering’s dry. That sequencing is what keeps the programme tight. It’s also why we can give you a date at the survey and stand behind it, rather than a vague “a couple of months” that quietly slides. If something does change, you hear it from one point of contact, not three.

Can You Speed Up a Loft Conversion?

Up to a point, yes. The fastest projects are the ones where the decisions are made before the scaffold arrives. If your design’s finalised, your fittings are chosen, and your approvals are in place, the build runs without the stop-start pauses that stretch a timeline. The delays almost always come from changes made mid-build, not from the building work itself.

Choosing a conversion type that suits your roof also keeps things moving. A Velux conversion on a roof with good headroom is far quicker than forcing a complex dormer onto a property that isn’t ready for one. The survey is where we match the right type to your home, which is the groundwork for a fast, clean build, and it costs you nothing to find out where your project stands.

What you can’t safely rush is the structural work, the drying time for plaster, or a council planning decision. A firm that promises a finished loft in a fortnight is cutting a corner somewhere. A realistic timeline you can trust is worth more than an optimistic one that slips.

What Can Affect Your Loft Conversion Timeline

A few things move the dates either way. If your conversion needs planning permission rather than falling under permitted development, allow around eight weeks for the council decision before the build can start, as set out on the Planning Portal. A party wall agreement under the Party Wall Act 1996 with attached neighbours adds a notice period at the front of the job, and the government’s party wall guidance explains the notice times. Changing the specification midway, long lead times on a particular window or staircase, and a spell of bad weather while the roof’s open can all add days. Because we manage these from one place, we plan around them rather than letting them stall the whole job.

Frequently Asked Questions

How long does a loft conversion take from start to finish?

From the first site visit to a finished room, a typical project runs around ten to fourteen weeks. That breaks down into roughly two to four weeks for design, drawings and approvals, then six to eight weeks of building work for a standard dormer. Simpler Velux conversions are quicker, and larger L-shaped conversions take longer.

Can a loft conversion be done in 4 weeks?

A straightforward Velux conversion can be completed in around three to five weeks, since it keeps the existing roof and adds roof windows rather than rebuilding the structure. Dormer and hip to gable conversions involve more building work and realistically take six to eight weeks on site. The survey will tell you which type your loft suits and give you an honest timeline.

How long does a dormer loft conversion take?

A dormer loft conversion typically takes six to eight weeks of on-site work. The first four weeks cover the structural work, the dormer build and making the roof weathertight. The second four weeks cover insulation, plastering, the staircase, any bathroom, and final decoration before building control signs the work off.

How long does it take to get planning permission for a loft conversion?

When planning permission is needed, the council typically takes around eight weeks to reach a decision once a valid application’s submitted. Many loft conversions don’t need it at all and proceed under permitted development, which removes this step entirely. We confirm which route applies to your home during the survey and handle the application for you if one’s required.

Do loft conversions take longer in a conservation area?

They can, because a conservation area usually removes permitted development rights, so you’ll need full planning permission rather than a quicker certificate. That adds the council decision time, around eight weeks, to the front of the project. The building work itself takes the same time. We check your area’s status at the survey so the timeline you’re given already accounts for it.

Get an Accurate Timeline for Your Home

The figures here are reliable guides, but the only way to get a date you can plan around is a survey of your actual loft. Our free, no obligation survey covers the roof structure, the type of conversion that suits the space, whether planning permission’s needed, and a week-by-week programme for your project.

You’ll get a fixed price alongside the timeline, so neither the cost nor the schedule drifts once we start. Sometimes a loft’s simpler than expected and the job moves quickly. Sometimes there’s structural work or a planning step that adds time, and we’ll be upfront about that from the first visit rather than discovering it halfway through.