Loft Conversion Cost Guide for 2025

See the real costs of different loft conversion types and learn what shapes your budget. Start planning your loft project with confidence today.

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How much does a loft conversion cost?

Understanding the true cost of a loft conversion is essential when planning your project. In this guide, we cover the latest average prices for different types of loft conversions, break down key factors that affect your budget, and highlight hidden costs you should be aware of.

Use our expert-backed resource to plan your loft conversion with confidence and avoid unexpected surprises.

Loft conversion costs by type

Understanding the average cost of different types of loft conversions is key when planning your project. Whether you're considering a simple Velux window installation or a full Mansard extension, the type of loft conversion you choose will significantly impact the final price.

Below, we break down the latest average costs, timescales, and cost per m² to help you plan your budget confidently in 2025.

Type of Loft Conversion (30m²) Average Cost Timescale (weeks) Cost Range Cost per m²
Velux £35,000 4–6 £27,500–£50,000 £1,167–£1,667
Dormer £50,000 6–8 £40,000–£60,000 £1,333–£2,000
Hip to Gable £55,000 8–10 £40,000–£70,000 £1,333–£2,333
Bungalow £50,000 8–10 £40,000–£60,000 £1,333–£2,000
Modular £60,000 2–3 £53,000–£100,000 £1,767–£3,333
Mansard £65,000 10–12 £50,000–£80,000 £1,667–£2,667
Shell £25,000 4–6 £20,000–£30,000 £667–£1,000
Terraced House £45,000 6–8 £30,000–£60,000 £1,000–£2,000
Maisonette £55,000 8–12 £45,000–£70,000 £1,500–£2,333

*Check out the various types of loft conversion, whether it's a Dormer, a Mansard, hip to gable, modular, or a Velux - we have trusted, experienced and verified specialists to provide a detailed quote for you - we also delve into the detail and you can look at Velux loft conversion costs and dormer loft conversion costs specifically.

Use our loft conversion calculator to generate an accurate quote for your conversion.

Cost breakdown for a loft conversion

Getting a loft conversion isn’t just about the main build, there are extra costs. Every stage has a price tag, from architect fees and structural calculations to VAT and finishing touches. This section breaks down each expense so you know exactly what to budget for and where your money will go.

Item Estimated Cost (£) Notes
Reinforcing joists & floors £2,500 - £5,000 Strengthening the existing floor structure is essential to support the additional weight of a loft conversion and ensure long-term stability.
Roof modifications & steel beams £3,000 - £7,500 If your loft conversion involves altering the roof structure, steel beams and reinforcements will be required to maintain the building’s integrity.
Velux or dormer windows £1,000 - £3,500 Installing roof windows improves natural light and ventilation. Costs depend on the type, size, and glazing options chosen.
Fire-resistant insulation materials £1,500 - £3,000 Insulation is a legal requirement for energy efficiency and fire safety, reducing heat loss while meeting UK building regulations.
Traditional wooden staircase £2,000 - £4,000 A full-sized staircase provides safe and easy access to the loft, with costs varying based on design, material, and finishes.
Space-saving staircase (e.g., spiral) £1,500 - £3,000 A compact alternative for smaller lofts, spiral or alternating tread staircases save space while complying with safety regulations.
Plastering & painting £2,000 - £4,000 Plastering smooths the walls and ceilings before painting, creating a polished finish that enhances the loft’s appearance.
Flooring (laminate, carpet, wood) £1,000 - £2,500 Flooring costs depend on the material chosen, with wood and laminate being more expensive but offering a durable and stylish finish.
Bespoke storage or fitted furniture £1,500 - £4,500 Custom-built wardrobes, shelving, or storage solutions maximise space and improve the loft’s functionality.
Adding a bathroom £4,000 - £8,000 Installing a bathroom in your loft conversion requires plumbing, waterproofing, and ventilation, with costs depending on fixtures and fittings.
Lighting fixtures & electrical wiring £2,000 - £4,500 Electrical work includes installing sockets, lighting, and wiring, ensuring compliance with Part P of UK building regulations.
Architectural plans £1,500 - £3,000 Professional drawings are needed for planning permission, structural calculations, and compliance with building control regulations.
Building control & inspections £400 - £900 Local authority or private building control officers must inspect key construction stages to certify compliance with UK regulations.
Party Wall Agreement (if applicable) £700 - £1,500 If your home shares a wall with a neighbour, a legal Party Wall Agreement may be required before construction begins.

Loft conversion costs by house type

Loft conversion costs vary depending on the size, structure, and location of your home. Some properties need extra structural work, while others can be converted more easily. Here are typical examples based on different property types to help you plan your project more accurately:

Loft conversions by house type

Semi-detached house

Semi-detached homes are ideal for adding a rear dormer, creating a full-size bedroom and ensuite without major structural work.

  • Velux loft conversion: £30,000–£40,000
  • Rear dormer loft conversion: £40,000–£55,000

Detached house

Detached houses offer flexibility but often need additional steel supports or structural work, especially for hip-to-gable extensions.

  • Velux loft conversion: £35,000–£45,000
  • Hip-to-gable + rear dormer: £55,000–£75,000

Terraced house

Victorian and Edwardian terraces are perfect for rear or L-shaped dormers, often creating space for a master bedroom and a compact shower room.

  • Full loft conversion with dormers: £45,000–£60,000
  • Modular loft extension: £65,000–£90,000

Maisonette (Upper floor flat)

Maisonette loft conversions usually require planning permission, but they can add valuable living space without extending the building's footprint.

  • Velux-only loft conversion: £28,000–£38,000
  • Dormer conversion: £40,000–£55,000

New build homes

New build homes often have trussed roofs, which require extra reinforcement. This can affect both the complexity and the cost.

  • Velux loft conversion: £30,000–£40,000
  • Dormer loft conversion: £40,000–£55,000

Detached homes and bungalows give the most creative freedom but usually involve higher structural costs. London and South East prices are typically 15–25% higher than national averages.

Loft conversion costs

Loft conversion costs: What impacts the price?

No two loft conversions cost the same. The final price depends on several key factors, from the type of conversion you choose to the materials, labour, and planning requirements.

Structural work, insulation, and finishing touches can all push costs up or down. Understanding what drives the price helps you budget better and avoid unexpected expenses. Let’s break it down.

Type of loft conversion

The more structural changes required, the higher the cost. The cost of a Velux conversion (adding roof windows) is the most budget-friendly.

While a Mansard conversion, which involves rebuilding the roof, is at the top end of the price range. Depending on the size and design, Dormer and Hip to Gable conversions fall somewhere in between.

Takeaway: Simpler loft conversion types like Velux cost less, while Mansard conversions require extensive work and bigger budgets.

Size and complexity

A larger loft conversion needs more materials, more labour, and longer build times—all of which increase costs. If your loft layout is unusual or requires multiple levels, expect additional engineering, planning, and construction expenses.

Takeaway: The bigger and more complex the loft, the higher the overall cost due to extra materials and labour.

Roof structure and pitch

Your existing roof design significantly affects how expensive your conversion will be. A steep-pitched roof usually has plenty of headroom, making conversion easier and cheaper. Low-pitched or trussed roofs, however, often require structural reinforcements, adding thousands to the cost.

Takeaway: If your loft already has good headroom and support, your costs will be lower. Flat or trussed roofs need extra work, increasing the price.

Planning permissions

Most loft conversions fall under permitted development, meaning you don’t need planning permission. However, if your project involves significant alterations, is in a conservation area, or exceeds certain size limits, you’ll need planning approval, which adds time and fees to your project.

Takeaway: If your loft conversion sticks to permitted development rules, you’ll avoid extra planning costs.

Planning permissions

Material choices

Your choice of windows, insulation, flooring, and finishes directly impacts costs. Basic uPVC windows are cheaper than bespoke timber options, and premium insulation materials add to the upfront cost but save on energy bills in the long run.

Takeaway: Higher-end materials cost more but last longer and improve your home’s efficiency and value.

Structural changes

Some homes need reinforced joists, steel beams, or adjusted rooflines to support a loft conversion safely. These modifications are essential but can add thousands to the overall budget.

Takeaway: If your loft needs major structural work, be prepared for higher costs and a longer build time.

Accessibility and site conditions

If your loft is difficult to access, builders may need extra scaffolding, cranes, or specialist equipment, increasing labour costs. Older homes and properties in tight urban spaces can also make construction trickier and more expensive.

Particularly tricky in big cities, the costs of a loft conversion in London can be massively impacted.

Takeaway: The easier your loft is to access, the cheaper and faster the conversion will be.

Contractor selection

Experienced loft conversion specialists may charge more upfront, but they help avoid costly mistakes and delays. A cheaper contractor might cut corners, leading to higher costs in the long run for repairs or corrections.

Takeaway: Hiring an experienced professional costs more initially but saves money over time.

Energy efficiency upgrades

Adding triple-glazed windows, better insulation, or solar panels increases initial costs, reduces energy bills, and boosts long-term home value.

Takeaway: Spending more on energy-efficient upgrades can save you money in the long run.

Market conditions

Loft conversion prices fluctuate based on labour demand, material shortages, and economic factors. Booking builders in advance and sourcing materials early can help lower costs.

Takeaway: If possible, plan your loft conversion during a stable market period to avoid price surges.

Accessibility & site conditions

Hidden costs to watch for during a loft conversion

Loft conversions often come with extra costs that aren’t immediately obvious when you start planning. Understanding these hidden expenses can help you budget accurately and avoid any financial surprises.

Hidden Cost Estimated Range (£) What It Covers
Party Wall Agreement £700–£1,500 Needed if you share a wall with neighbours.
Building Control Fees £400–£900 Required inspections during key build stages.
Planning Permission (if needed) £200–£400 Only required for designs outside permitted development.
Structural Engineer Reports £500–£2,000+ For complex designs needing additional calculations.
Energy Efficiency Upgrades £1,000–£3,000 Meeting the latest insulation and energy standards.
Utility Relocation Costs £500–£2,000 Moving boilers, rerouting plumbing, and rewiring electrics.
Scaffold and Access Solutions Varies Special scaffold setups for tricky sites.
Decoration and Finishing Touches £1,500–£4,000 Painting, flooring, and interior finishes.
Insurance Policy Updates Small additional premium Required after expanding your living space.

How to reduce the cost of your loft conversion

Loft conversions can boost your home's value and functionality without a hefty price tag. With smart choices and cost-effective strategies, you can achieve your dream loft conversion on a budget.Here are seven ways you can reduce the cost of your dream loft conversion:

Compare quotes

Get multiple quotes from different contractors to secure the best price. Comparing quotes can also give you an edge in negotiations, ensuring you get the most cost-effective deal for the same quality of work.

Simplified design

Opt for a simpler conversion like Velux, which does not require significant changes to the roof structure. This can notably reduce both the time and costs involved. Small loft conversions can be the way forward when looking for a simplified design.

DIY elements

You can undertake non-structural work, such as painting, decorating, or fitting finishes. This hands-on approach can lower labour costs, though it demands time and some DIY skills.

Reuse materials

Seek opportunities to use reclaimed or second-hand materials, which can be much cheaper than new ones. Salvage yards, online marketplaces, or local building projects clearing out excess supplies can offer quality materials at reduced costs.

Flexible timing

Arrange your project during a contractor's off-peak periods, typically in winter or late autumn, when business is slower. During these times, contractors might provide discounts or be more open to negotiating prices.

Group discounts

Enquire with your contractor if there are discounts for buying materials in bulk or through their trade accounts, which often have more favourable rates than retail.

Planning

Comprehensive planning before beginning the work can prevent costly modifications and delays during the project. Ensure your design, budget, and agreements with contractors are finalised to avoid unforeseen costs.

You'll also need to consider planning permission and regulations on your windows for your loft conversion too.

Discover financing options for your loft conversion today.

Loft conversion timescales: How long will it take?

The time it takes to complete a loft conversion depends on the type of build, the project's complexity, and the property’s structure. Simple Velux conversions are typically quicker, while larger dormer or mansard conversions take longer to complete.

Type of Conversion Typical Timescale
Velux Conversion 4–6 weeks
Dormer Conversion 6–8 weeks
Hip-to-Gable Conversion 8–10 weeks
Mansard Conversion 10–12+ weeks

Read our detailed guide on loft conversion timelines to understand exactly what to expect when looking at each type of loft conversion and expected delivery timescales.

How to budget for a loft conversion

A loft conversion is a big investment, and managing your budget properly helps avoid overspending and hidden costs. Careful planning ensures you control your finances while getting the most from your project. Here’s how to budget smartly:

  • Create a detailed cost plan – Break down every expense, including materials, construction, VAT, and professional fees. Getting itemised quotes from contractors prevents underestimating costs.
  • Set aside a contingency budget – Unexpected costs are common in loft conversions. A 10–15% buffer helps cover surprises like structural reinforcements, delays, or material price changes.
  • Compare multiple contractor quotes – Always get at least three quotes from reputable builders. Be cautious of cheaper estimates; they may leave out key costs or use lower-quality materials.
  • Plan for hidden costs – Beyond construction, factor in planning permissions, building control fees, interior finishes, and insurance premium increases. If work is extensive, temporary accommodation costs may also apply.

Planning, comparing costs, and preparing for the unexpected will keep your loft conversion on track financially while avoiding budget shocks.

Future maintenance costs for a loft conversion

A loft conversion isn’t just a one-time expense—like any part of your home, it needs ongoing upkeep to stay efficient, comfortable, and in good condition.

Factoring in future maintenance costs now can help you budget and avoid expensive repairs later. Here are our key considerations: 

Maintenance Area Estimated Cost (£) Details
Roof Maintenance £150–£500 per year Regular roof inspections help catch small leaks before they cause water damage. Areas around dormers, skylights, and chimneys are most prone to wear.
Heating & Insulation Efficiency £100–£300 every 5–10 years Loft insulation settles over time, reducing its effectiveness. Replacing or topping it up helps keep heating costs low.
Structural Integrity £0–£500 (if repairs needed) All buildings settle over time, and loft conversions add weight to existing structures. Checking for cracks, movement, or sagging helps prevent bigger issues.
Window Upkeep £50–£250 per year Velux and dormer windows need regular cleaning, resealing, and occasional hinge replacements to stay weatherproof and energy-efficient.

Planning, comparing costs, and preparing for the unexpected will keep your loft conversion on track financially while avoiding budget shocks.

Financing Option Description Pros Cons
Savings Using personal savings to fund the project. No interest costs; immediate availability. It can deplete personal funds.
Personal Loan Obtaining a fixed-rate loan from financial institutions. Quick access to funds; fixed repayment terms. Higher interest rates may apply; impacting credit rating.
Home Equity Loan Borrowing against the equity built up in your home. Lower interest rates; potential tax deductions. Risk of repossession if repayments are missed.
Remortgaging Increasing your mortgage to release equity for funding. Access to larger sums at potentially lower rates. Long-term increase in debt; possible fees.
Construction Loan A loan that releases funds in stages as construction progresses. Payments aligned with project milestones. Typically, higher interest rates; complex application process.

Loft conversion costs: Wrapping it up

A loft conversion is an investment that adds space, comfort, and value to your home. Costs vary depending on the type of conversion, materials, and structural work required.

Understanding these cost factors allows you to budget effectively and avoid unexpected expenses. Whether working with a tight budget or planning a luxury upgrade, making informed choices can save money in the long run.

Next steps: 

Loft conversion costs and prices - frequently asked questions

Here's everything you need to know about loft conversion costs in the UK, answered in our frequently asked questions:

Why do loft conversions cost so much?

Loft conversions involve making structural changes, installing insulation, updating electrics and plumbing, and adding detailed finishes. All of which require skilled labour and high-quality materials. These combined factors drive up the overall cost.

What’s the cheapest type of loft conversion?

A Velux (roof light) loft conversion is usually the most affordable option. It requires minimal structural changes and adds light and space without major construction work.

How much does a loft conversion cost per square metre?

In the UK, loft conversion costs typically range from £1,200 to £2,000 per m², depending on the type of conversion, materials used, and your location.

How much value can a loft conversion add to my home?

A well-executed loft conversion can add between 15% and 25% to your home's market value, especially if it creates additional bedrooms or bathrooms.

Why do loft conversion costs vary across the UK?

Labour and material costs differ between regions. Areas like London and the South East often have higher conversion costs due to greater demand for skilled trades and premium finishes.

What are the financial benefits of a loft conversion?

A loft conversion increases your property's value and saves you the high costs associated with moving house. Many homeowners recoup a significant portion of their investment when selling.

What hidden costs should I factor into my budget for a loft conversion?

Additional expenses can include party wall agreements, building control fees, structural reinforcements, utility upgrades, interior decoration, and insurance updates.

Is a loft conversion cheaper than buying a new house?

Yes, a loft conversion is usually cheaper than moving. It avoids costs like stamp duty, legal fees, and moving services, while adding valuable living space and long-term home value.

Do I need planning permission for a loft conversion?

Most loft conversions fall under permitted development rights and do not require planning permission. However, larger conversions or homes in conservation areas may need formal approval.