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Shell Loft Conversion: What Is It, Costs & Process
- A shell loft conversion means installers handle the structural work while the homeowner takes care of plastering and decorating.
- Opting for this type of conversion can lower costs by 20% to 30%, depending on your expertise and material choices.
- Adding a loft conversion can boost your property’s value by up to 20%.
Dreaming of extra space without breaking the bank? A shell loft conversion might be the perfect solution.
It gives you the best of both worlds—professionals handle the heavy lifting with structural work while you take control of plastering and decorating to save money.
This option lets you save 20–30% while creating a space that’s uniquely yours, with expert help where it’s needed most.
In this guide, you’ll discover exactly how a shell loft conversion works, how much it can save you, and why it’s a smart choice for budget-savvy homeowners.
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What exactly is a shell loft conversion?
A shell loft conversion creates the basic structure of a loft, leaving the finishing work to the homeowner.
The contractor handles tasks like roofline restructuring, floor reinforcement, and installing beams and supports. They also take care of feasibility assessments, planning permissions, building regulations, and structural work.
Once completed, the space is left as a blank canvas with the walls ready for plastering or painting, floors prepared for your choice of covering, and no fixtures or decorations installed.
This approach reduces costs by 20–30% compared to the average loft conversion cost and allows you to personalise the interior with your own materials, design, and style.
Keep in mind that not all types of loft conversion are suitable for a shell conversion. Typically, Velux, dormer, hip-to-gable, and mansard conversions can be done as shell conversions, but the suitability depends on the complexity of the project:
- Velux windows loft conversions: Ideal for a shell conversion since they primarily involve installing roof windows and minimal structural changes.
- Dormer conversions: Commonly done as shell conversions, as the contractor can handle the dormer structure, leaving the interior finishing to the homeowner.
- Hip-to-gable conversions: These involve more structural work but can still be suitable for a shell approach if the contractor completes the roof adjustments.
- Mansard conversions: Often more complex, but they can be done as shell conversions if the contractor handles the extensive structural modifications required for the steeper roof slope.
On the other hand, roof lift conversions or projects with major structural changes may not be suitable for a shell conversion. These types of conversions involve advanced engineering and detailed finishing, which often require professional expertise from start to finish.
What does a shell loft conversion include?
Here’s what’s typically included in a shell loft conversion:
- Structural framework: Roof alterations, floor joists, and walls to ensure stability and compliance with building regulations.
- External finishes: Installation of windows, doors, and roofing to make the space weatherproof.
- Basic services (if agreed): Some contractors may install a staircase and cap off basic electrical and plumbing services.
What is not included in a shell conversion?
Once the structural work is complete, the rest of the project is up to the homeowner. This phase focuses on personalising and completing the space.
Here’s what’s not included:
- Plastering: Walls are left ready for plastering or finishing.
- Flooring: You’ll need to lay your chosen flooring materials.
- Second fix carpentry: Tasks like fitting skirting boards or doors are excluded.
- Painting and decorating: Interior painting, wallpapering, and decorative finishes are left to you.
- Final fixtures: Installing light fittings, switches, sockets, and plumbing fixtures is not covered.
Search for pre-owned doors, windows, and light fixtures on platforms like eBay, Facebook Marketplace, or local reclamation yards. These items are often in excellent condition and come at a fraction of the price of new products.
How much does a shell loft conversion cost?
On average, a 20 m² shell loft conversion costs between £25,000 and £35,000 for a dormer, £45,000 to £70,000 for a mansard, and £30,000 to £40,000 for a hip-to-gable conversion.
These prices are significantly lower than full-service loft conversions because shell conversions reduce both labour and material costs.
By finishing the interior yourself, you can save 20–30% compared to a fully completed project, according to Milestone Homes & Lofts.
However, it's essential to carefully budget for the materials and tools needed for the DIY loft conversion, such as plastering, flooring, or decorating. For instance, sourcing materials from local suppliers or buying in bulk can help keep the shell loft conversion price down.
To help you estimate, here’s a table comparing typical loft conversion costs with shell conversion costs for different types of projects. These figures can serve as a starting point when planning your budget:
| Conversion type | Average full conversion cost for 20 m2 | Average shell conversion cost for 20 m2 |
|---|---|---|
| Velux | £15,000 to £20,000 | £10,500 to £16,000 |
| Dormer | £25,000 to £35,000 | £17,500 to £28,000 |
| Mansard | £45,000 to £50,000 | £31,500 to £36,000 |
| Hip to gable | £30,000–£40,000 | £21,000 to £32,000 |
The final shell loft conversion cost in the UK depends on factors like the type and size of the conversion, location, project complexity, material quality, and the homeowner's DIY skills.
With many factors influencing loft conversion shell cost, obtaining multiple quotes is essential for staying within budget. Vendors can vary significantly in pricing, so comparing options ensures you find the right professional at the best price.
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What steps are involved in a shell loft conversion?
A shell loft conversion involves several key steps to ensure the project is completed efficiently and meets all necessary standards.
Here’s a concise breakdown of the process:
- Full site survey: The contractor assesses feasibility, measures the space, checks if planning permission is needed, and ensures compliance with regulations.
- Technical and structural planning: Structural engineers create detailed drawings, perform structural calculations, and ensure compliance with building regulations for fire safety, energy efficiency, and ventilation.
- Disassembly and scaffolding: The existing roof is removed, and scaffolding for loft conversion is erected to support the construction process.
- Construction phase: New steel beams, floor joists, insulation, ventilation, windows, doors, and a staircase are installed, forming the structure of the loft.
- Roof tiling: Roof tiles are applied to waterproof the structure, and materials like GRP or felt are used for flat roof sections to blend with the existing roof.
- Site clear-up and inspection: The site is cleared of debris, and a final quality check ensures all work meets the agreed standards.
- Creative DIY phase: Homeowners take over to complete interior finishing, including plastering, flooring, decorating, and installing plumbing, wiring, and fixtures.
Is a shell loft conversion the best option for you?
A shell loft conversion offers a cost-effective solution for homeowners looking to save 20–30% on their project.
It includes all essential structural work—such as roof alterations, floor joists, insulation, and external finishes—leaving the interior plastering, decorating, and final fixtures to the homeowner.
This option is ideal if:
- You’re working with a limited budget but still want a high-quality conversion.
- You have some DIY skills or are willing to learn for tasks like plastering, painting, or flooring.
- You want to customise the space to your own taste and timeline.
However, it may not suit those who lack the time, tools, or confidence to handle finishing tasks themselves. If you're ready to take on the challenge, a loft shell conversion can be a great way to achieve a unique loft conversion on a budget.
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