How Long Should a Loft Conversion Take?

A loft conversion could be the perfect solution if your home is starting to feel a little cramped—whether due to a growing family, a new home office, or simply the need for more space. It's one of the most cost-effective ways to expand your living area without the hassle of moving house.

But before diving in, you may be wondering: how long does a loft conversion take? The answer depends on several factors, including the type of conversion you choose, your home's existing structure, and any necessary planning approvals.

In this guide, you'll discover typical loft conversion timescales, the benefits of converting your loft, and what to expect from the process—from initial planning to the final build.

Why Choose a Loft Conversion? The Key Benefits

Let's consider why loft conversions worth considering. A new loft conversion lets you stay in the neighbourhood you love and gain valuable extra living space. This is so much easier and more cost-effective than moving to a bigger house in a different area.

Here are some key benefits of converting your loft:

• Increase Your Home's Value – A well-executed loft conversion can add up to 20% to your property's value, making it a fantastic investment.

• Create More Living Space – Whether you need an extra bedroom, a home office, or a playroom for the kids, a loft conversion transforms underused existing space into something functional and stylish.

• Enjoy Stunning Views – Being at the highest point in your home, a loft conversion often offers better views than any other room.

• No Need for Planning Permission (In Most Cases) – Many loft conversions fall under permitted development rights, meaning you can extend your living space without the hassle of applying for planning permission (though some exceptions apply—more on this later).

Before jumping in, ensure your loft is suitable for conversion. Check your roof height, roof pitch, and structural integrity to see if they can all accommodate a proper loft conversion. You can assess these yourself or ask a professional builder.

Once you know your loft is suitable, the next question is:

How Long Does a Loft Conversion Take? A Breakdown by Type

Some conversions are relatively straightforward, while others involve extensive roof modifications and take longer to complete. Here's a breakdown of different loft conversion types and their estimated completion times:

1. Roof Light (Velux) Loft Conversion – 4 to 6 Weeks

If you only want a quick, cost-effective way to convert your loft, a roof light (Velux) conversion is your best option. This method involves adding skylight-style windows to your existing roof without changing its structure.

• Why choose it? Minimal disruption, lower costs, and no need for major structural changes.

• Estimated timeframe: 4 to 6 weeks, depending on the number of windows and any additional work required.

2. Dormer Loft Conversion – 5 to 6 Weeks

A dormer conversion extends the existing roof by adding a box-shaped structure that protrudes outward, creating extra headroom and floor space. This type of conversion is ideal if you need a larger, more functional loft area.

• Why choose it? Increases usable space significantly and allows for bigger windows.

• Estimated timeframe: 5 to 6 weeks for smaller dormers, but larger ones or multiple dormers could take up to 10 to 12 weeks.

3. Hip-to-Gable Loft Conversion – 6 Weeks

If your home has a hipped roof (sloping on all sides), a hip-to-gable conversion extends the roof by converting one of the sloping sides into a vertical gable wall. This adds valuable headroom and makes the loft feel more spacious.

• Why choose it? Works well for semi-detached and detached homes with hipped roofs.

• Estimated timeframe: Around 6 weeks, though larger homes may take slightly longer.

4. Mansard Loft Conversion – 7 to 8 Weeks

A Mansard conversion is the most extensive type of loft conversion, often requiring a complete roof replacement. It alters the roof's structure to create a nearly vertical wall on one side, maximising interior space and making the loft feel like a full additional storey.

• Why choose it? Ideal for creating a spacious and luxurious loft area, often used for master bedrooms with en-suites.

• Estimated timeframe: 7 to 8 weeks due to the complexity of the structural changes.

Choosing the Right Loft Conversion for Your Needs

A Velux or dormer conversion may be the best choice if you're looking for a quick and simple conversion. However, if you want to maximise space and create a more permanent addition to your home, hip-to-gable or Mansard conversions are well worth considering—just keep in mind the longer build times.

The next step is to ensure that your loft is suitable for conversion. Next, we'll examine the key factors that influence the length of your project.

How Long Does the Planning & Design Stage Take?

Before the actual construction of your loft conversion begins, there's an essential phase that takes time but ensures a smooth and hassle-free build: the planning and design stage. The duration of this stage depends on how clear your vision is, whether you need planning permission, and how quickly local authorities process applications.

1. Designing Your Loft Conversion (2 to 6 Weeks)

The first step in any loft conversion is the design process. You might already have a clear idea of what you want, or you may need guidance from a professional designer, architect, or loft conversion specialist.

• What happens in this phase?

  • A survey of your loft and home is conducted to assess space, headroom, fire safety, and structural suitability.

  • The design team drafts multiple layout options, helping you decide on the best use of space.

  • You finalise your preferred design, ensuring it suits your lifestyle and property type.

  • Detailed blueprints and structural calculations are prepared for building regulations and planning applications if required.

2. Planning Permission & Building Regulations (8 to 13 Weeks, If Required)

Many homeowners worry about planning permission, but not all loft conversions need it. Simple conversions—such as Velux or small dormer extensions—often fall under permitted development rights, meaning you can proceed without a lengthy approval process.

However, planning permission will be required if your plans involve major structural changes (e.g., a hip-to-gable or Mansard conversion) or if your home is in a conservation area.

• How long does planning permission take?

  • Most planning applications take 8 weeks to process, though complex or large projects may take up to 13 weeks.

  • If your initial application is rejected due to non-compliance with relevant regulations, you may need to revise and resubmit, which will add further delays.

  • Working with an experienced architect or loft conversion specialist can help ensure compliance from the start, reducing the risk of rejection.

Even if planning permission isn't needed, building regulations approval is required for all loft conversions. This ensures the structure is safe and meets fire safety, insulation, and accessibility standards. Your local building control office will inspect the project at key stages to sign off on the work.

3. Scheduling the Project (1 to 2 Weeks)

Once the design is finalised and any necessary permissions are in place, the next step is scheduling. Your loft conversion company will set a start date, arrange for materials to be ordered, and confirm the estimated completion time. Delays at this stage are rare, but the availability of builders and supply chain issues may impact the project's timeline.

How to Speed Up the Planning & Design Process

• Hire experienced professionals – Architects, designers, and builders familiar with loft conversions can help streamline the process.

• Know whether you need planning permission – If your project falls under permitted development, you can skip the 8 to 13-week approval process.

• Ensure your plans are fully compliant – Getting everything right the first time avoids delays caused by rejected applications.

• Have a clear vision – The more decisive you are during the design phase, the faster things can progress.

With the planning phase complete, your project is ready to move to the construction phase—where the real transformation begins!

The Building Phase: What to Expect During Construction

Once all approvals are in place, the actual construction begins. At this stage, your builder will provide a full schedule of works, detailing each step of the process so you'll know exactly what to expect.

The typical sequence of work includes:

1. Structural work – Reinforcing the existing roof structure and making any necessary exterior modifications.

2. Internal roof work – Insulating, installing ventilation, and reinforcing the loft space.

3. Installing the staircase – Creating access to the new loft room.

4. Breaking through – Connecting the new loft space to the rest of the house.

5. Interior work – Adding walls, flooring, lighting, built-in storage, and final fixings.

6. Decorating and finishing – Painting, plastering, and adding any final touches.

Loft Conversion Timeline: A Week-by-Week Breakdown

Every loft conversion is unique, but most follow a general timeline that gives you an idea of what to expect throughout the process. While smaller, more straightforward conversions (like a Velux or dormer conversion) may take as little as four weeks, more complex loft conversion projects (such as a Mansard or hip-to-gable conversion) can take up to eight weeks or more.

Below is a breakdown of the loft conversion process:

Weeks 1 & 2 – Preparation and Structural Work Begins

The first stage involves setting up the site, organising materials, and ensuring everything is in place for work to begin.

• Site preparation – A skip is delivered, scaffolding is erected, and materials begin arriving.

• Roof access created – In many cases, a hole is made in the roof to allow workers to access the space externally, minimising disruption inside your home.

• Structural reinforcements – Depending on the conversion type, initial support work begins to strengthen the roof and floor structure.

At this point, most of the work happens outside the home, meaning you'll experience minimal disruption. By the end of the second week, the foundation of your loft's new structure should be in place.

Weeks 3 & 4 – Interior Work Begins

This is when your loft space starts to take shape internally.

• Floor joists installed – A solid base is built for your loft's new flooring.

• Insulation & ventilation fitted – Ensuring your loft is comfortable and energy-efficient.

• Walls constructed – Stud walls are installed to define the room's layout.

• Window installation – For Velux and dormer conversions, this is the stage where windows are fitted.

At this stage, simpler loft conversions may be nearing completion. Smaller projects that don't require extensive structural changes could be ready for finishing touches by the end of week 4.

Weeks 5, 6 & 7 – Staircase Installation & Finishing Works

For longer conversion processes, this phase involves connecting the loft to the rest of the house and finalising all key installations.

• Staircase installation – Your new loft space is made accessible from inside the house.

• Plastering & finishing walls – The interior starts to look like an actual room.

• Electrical & plumbing work – Lights, sockets, and any required plumbing (for en-suite bathrooms) are installed and tested.

• Carpentry work – Doors, skirting boards, and built-in furniture are added.

At this point, your loft is fully functional, and only the final touches remain.

Week 8 & Beyond – Decorating & Final Fixes

The last stage is all about making the space feel like home.

• Painting & decorating – Walls are painted, flooring is laid, and final details are completed.

• Fixtures & fittings installed – Any remaining furniture, shelving, or custom features are added.

Once everything is complete, your brand-new loft space is ready to use!

Total Timeframe for a Loft Conversion

• Smaller loft conversions (Velux, dormer) – 4 to 6 weeks

• Mid-sized conversions (Hip-to-gable) – 6 to 7 weeks

• Large, complex conversions (Mansard, multiple rooms) – 7 to 8+ weeks

For more extensive projects—such as lofts with multiple rooms or a roof terrace—extra time may be needed. Still, most homeowners can set realistic expectations and have their new loft space completed within one to three months.

Why Hiring Professionals for Your Loft Conversion Matters

While you might be tempted to look for the fastest turnaround time, quality should always come first for a loft conversion. A professionally handled conversion ensures that structural integrity, safety, and building regulations are all met—giving you peace of mind that your new space is both beautiful and built to last.

A reputable loft conversion company will handle planning and design, ensure high-quality workmanship, and provide a realistic timeline.

Budgeting properly is key. On average, you can expect to pay between £27,500 and £75,000, with more extensive projects sitting at the higher end.

Though starting a project of this scale may feel overwhelming, choosing the right professionals makes all the difference—helping you create a stunning, high-quality loft conversion with minimal stress.