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How Long Will Your Loft Conversion Take?

July 21, 2025

You have decided that you need more space. You don’t want the upheaval of moving house, not to mention the hidden extra costs that will be involved! The solution? Transform your loft into a spacious luxury bedroom or something more practical like an office – or even indulge yourself with a hobby room.

When our customers ask how long their loft conversion will take, the simple answer is that it depends. The type of conversion you choose, the size and complexity, along with the planning and building control processes required to move forward with the project all play a part. In this blog we break it down so you know what to expect and how to plan accordingly.

WORKING WITH YOUR CIRCUMSTANCES

Factors that Affect Loft Conversion Timescales

Whilst we have an average timeline, there will be deviations from this as no two conversions are the same. There are elements that can speed up or slow down the loft conversion:

Planning Permission & Building Regulations: In some cases, planning permission is not always needed at this time. If this is the case we will apply for a certificate of lawful development (CLD) which confirms planning permission was not needed at the time we built your loft. Ultimately the council makes the final decision, which will take a number of weeks. If they decline the CLD then they may ask for full planning to be submitted. Again this can then add more time.

Party Wall Agreements: If your property shares a wall with next door then a party wall agreement will be needed. In some cases, neighbours will be satisfied with an informal letter from yourself. However, neighbours have been known to request a more formal approach. They can that a Party Wall Surveyor is used to draw up a Party Wall Agreement prior to the build. This agreement is between you and your neighbour – not the loft builder. We recommend you look at the following website for up-to-date information. https://www.gov.uk/party-walls-building-works

Weather Conditions: Whilst we aim to work as closely as possible to the initial lead time given, we do have to consider weather conditions. Occasionally adverse weather can result in some delays.

Custom Features: Bespoke joinery, built in wardrobes, ensuites etc can increase build time slightly. Some customers request unplanned additional work during their build. In these cases we do not know exactly how long a loft will take to complete ahead of the actual build itself.

ESTIMATED TURNAROUNDS FOR DIFFERENT TYPES OF LOFT

Average Timeframes to complete Loft Conversions

1: Basic Rooflight or VELUX Conversion:

Time estimate: 6 to 8 weeks

The quickest and cost affective type of loft conversions involves adding skylight windows and reinforcement of the loft floor. There is no change to the shape of the roof or structure. As it is relatively straightforward, it often does not require planning permission but will need to be signed off by Building Control, something we can organise for you.

3: Hip-to-Gable Conversion:

Time estimate: 12 to 16 weeks

This is most common in semi-detached or end of terrace properties. It involves extending the sloped side of roof (hip) into a vertical wall (gable). It is a bigger structural change therefore the timeline is slightly longer.

2: Dormer Loft Conversion:

Time estimate: 12 to 13 weeks

Adding a Dormer will increase usable space and head height to areas of the loft that would not necessarily be used. A structural alteration such as building out a box-shaped extension from the existing roof accomplishes the required result. While this build is more complex than a rooflight conversion, they are still usually completed within the estimated lead time.

4: Mansard Loft Conversion:

Time estimate: 12 to 14 weeks

This is the most time-consuming conversion, involving major changes to the roofs structure and appearance. Typically located at the rear of the property a mansard conversion creates the maximum amount of space however required more time and expertise.

Final Thoughts

Loft conversions can take an estimated 6 to 16 weeks once construction begins, depending on the complexity of the build. Once you have signed up with us the planning, design and approvals may span anything around 6 months should everything go to plan. At Charles Grosvenor, we provide realistic timelines and a dedicated project manager to keep everything on track.
We will walk you through every stage from start to finish.