What are the average costs for a full loft Conversion in the UK?

Loft conversions are one of the most popular ways UK homeowners add valuable living space without extending outwards. Whether you’re looking to create an extra bedroom, a home office, a playroom, or even a self-contained suite, understanding how much a full loft conversion costs in the UK in 2026 helps you plan, budget smartly and avoid unexpected expenses.

In this guide we break down average costs, major factors that influence pricing, and tips to help you get the best value for your project.

Average loft conversion costs in the UK (2026)

Attic conversion prices vary widely depending on size, design, materials and the amount of structural work required. As of 2026, the typical cost ranges are:

Type of Loft Conversion	Average UK Cost (2026)
Basic conversion (Velux/rooflight)	£15,000 – £25,000
Dormer conversion	£25,000 – £45,000
Hip-to-gable conversion	£30,000 – £50,000
L-shaped / Mansard conversion	£40,000 – £60,000+
Luxury or bespoke conversion	£50,000 – £80,000+

These costs include design, materials, labour, insulation, electrics, plumbing (if required), flooring and finishing - though exact prices depend on your specifications and location.

Why loft conversion costs vary

Several key factors determine the overall price of your UK loft conversion:

1. Conversion Type

• Basic (Velux/rooflight): No change to roof shape - most cost-effective.

• Dormer: Adds space outwards - mid-range pricing.

• Hip-to-gable / L-shaped / Mansard: Structural roof changes - higher cost.

2. Size of the loft space

Larger lofts with higher head height generally cost more due to extra materials, labour and finishing work.

3. Building control & design fees

Architect or structural engineer fees, planning advice and building regulations compliance are necessary costs that add to the total.

4. Insulation, heating & ventilation

Modern regulations (Part L Conservation of fuel and power) mean good insulation and ventilation are essential — and add to cost.

5. Plumbing & electrics

If you’re adding an ensuite bathroom or extra heating, expect additional labour and materials.

6. Access & staircase costs

Loft access and a compliant staircase structure (needed for a legal habitable room) are often overlooked but important costs.

7. Finishes & fixtures

Choices such as flooring, tiling, quality of windows and decoration influence overall budget significantly.

Cost breakdown

Here’s a rough breakdown of how the total cost of a loft conversion tends to be spent:

Category	% of Total Cost
Construction & Structural Work	45%
Insulation, Flooring, Walls & Ceilings	20%
Windows, Rooflights & Joinery	10%
Electrics & Plumbing	10%
Design & Building Control	5–10%
Finishes (Paint, Skirting, Fixtures)	10%

What’s included in a loft conversion cost

A professional loft conversion estimate usually covers:

• Structural work (joists, beams, supports)

• Roof alterations (dormers, rooflights)

• Insulation & ventilation systems

• Fire safety upgrades

• Staircase installation

• Plastering & flooring

• Electrics (lighting, power points)

• Heating extensions or radiators

• Building control inspections & certification

Hidden costs to be aware of

Certain costs are commonly overlooked when homeowners first budget:

• Scaffolding: often essential for safety

• Loft clearance or debris removal

• Upgrading existing services: electrics, plumbing, heating

• Planning permission costs: only needed for certain configurations

• VAT on labour & materials

Factoring these into your initial budget prevents unwelcome surprises.

Is a loft conversion worth the cost?

Yes - for many UK homeowners, a well-executed loft conversion delivers excellent value:

• Adds living space without reducing garden area

• Boosts property value - often by 15–20%

• Improves energy efficiency with modern insulation

• Enhances lifestyle (extra room, home office, rental potential)

A loft conversion is often more cost-effective than moving to a larger home - particularly in high-value markets like the South West, South East and London.

Tips for reducing loft conversion costs

Want to keep costs manageable without compromising quality?

✔ Prioritise essentials

Focus on structural and insulation work first - leave cosmetic choices until later if needed.

✔ Compare multiple quotes

Get at least three detailed quotes to ensure competitive pricing and clear scope of works.

✔ Standardise materials

Custom or bespoke elements look great but can significantly increase cost.

✔ Schedule during quieter seasons

Contractors sometimes offer better rates outside peak renovation periods.

✔ Plan for the long term

Invest in quality insulation, windows and ventilation - they reduce energy bills over time.

How long does a loft conversion take?

Typically, depending on complexity:

• Basic Loft Conversion (Velux): 4–6 weeks

• Dormer Conversion: 8–12 weeks

• Complex Conversions (Mansard/L-shaped): 10–16+ weeks

Delays can come from bad weather, material lead times or late design decisions, so early planning is key.

A loft conversion is a significant investment, but when planned correctly it can transform how you live - adding valuable space, comfort and value to your home. In 2026, understanding realistic costs helps you plan effectively and renovate with confidence.

If you’re considering a loft conversion this year, start with clear cost expectations, multiple quotes, and a trusted contractor who understands your goals.

At SafeBuild, we provide tailored loft conversion designs, accurate cost estimates and professional installation across Dorset, Poole, Bournemouth and the South West. From concept to completion, we’ll help make your loft conversion smooth, stress-free and built to last.

Book your free consultation: safebuildrenovations.co.uk/loft-conversions

How much does a full loft conversion cost in the UK in 2026?

The average cost of a full loft conversion in the UK in 2026 ranges from £25,000 to £60,000+, depending on the type of conversion, size of the loft, materials used and structural requirements.

What is the cheapest type of loft conversion?

A Velux (rooflight) loft conversion is usually the most affordable option, typically costing between £15,000 and £25,000, as it doesn’t alter the roof structure.

Do loft conversion costs include stairs and insulation?

Yes, most full loft conversion costs include stairs, insulation, plastering, electrics and building control sign-off, but it’s important to check each quote carefully.

Is planning permission needed for a loft conversion?

Many loft conversions fall under permitted development, meaning planning permission isn’t required. However, dormer, mansard or listed properties may need approval.

How long does a full loft conversion take?

A typical loft conversion takes 6 to 12 weeks, depending on complexity, weather conditions and whether plumbing or bathrooms are added.

Does a loft conversion add value to a house?

Yes. A well-designed loft conversion can increase a property’s value by up to 15–20%, making it one of the most cost-effective home improvements in the UK.

Are loft conversions worth the cost compared to moving house?

In most cases, yes. A loft conversion is often far cheaper than moving and avoids stamp duty, legal fees and disruption - while allowing you to stay in your current home.

What factors affect loft conversion costs the most?

Key factors include:

• Type of conversion (Velux, dormer, mansard)

• Structural work required

• Size of the loft

• Plumbing and bathroom installation

• Quality of finishes