Thinking of expanding your home and adding value? A loft conversion is one of the most cost-effective ways to create extra space without moving. At Draw Architecture, we’ve developed a powerful, user-friendly Loft Conversion Cost Calculator to help you quickly estimate how much a loft conversion might cost based on your exact requirements.

Whether you're exploring a dormer loft extension, hip-to-gable, Velux, or mansard conversion, this guide dives deep into the different options, real UK costs, and the factors that influence your quote.

How Much Does a Loft Conversion Cost in the UK?

The cost of a loft conversion in the UK can vary widely depending on the type of conversion, the size of your property, and your location. On average, you can expect to pay anywhere from £20,000 to £85,000, depending on complexity and finish. For instance, a simple Velux loft conversion might cost around £20,000–£25,000, while a full Mansard loft extension could exceed £75,000. London and the South East generally command higher prices due to labour and material costs.

Our loft conversion cost calculator provides accurate, region-specific estimates. We factor in real market data and architectural insights, ensuring you're not surprised later in the design or construction phase. If you're wondering how much a loft conversion costs, this tool gives you a realistic starting point.

Average Loft Conversion Costs

Different types of loft conversions have different average price ranges. Here’s a helpful breakdown:

• Velux Conversion: £15,000 – £25,000
  
  
• Dormer Loft Extension Cost: £30,000 – £60,000
  
  
• Hip-to-Gable Conversion: £40,000 – £65,000
  
  
• Mansard Loft Conversion: £50,000 – £85,000
  
  
• L-Shaped Dormer: £45,000 – £75,000
  
  

These are general averages and can vary depending on your home's structure, accessibility, and finish quality. At Draw Architecture, we use our proprietary cost of loft conversion calculator to factor in real-world variables such as location, number of bathrooms, and structural modifications. We ensure the data is up-to-date with current UK construction rates, especially relevant in fluctuating material and labour markets.

Cost Factors That Affect Your Quote

Several key factors can significantly impact your loft conversion cost UK. Firstly, the type of loft conversion matters; a Velux is less invasive and cheaper, while a Mansard involves major roof restructuring. Then comes the property’s location, where homeowners in London, for example, often face higher costs.

Next, features like adding an ensuite bathroom, increasing head height, or choosing bespoke finishes can all raise the cost. Accessibility is another big one; homes with tricky access might need scaffolding or waste removal logistics, which influence the price.

Your specification level (basic vs. high-end) also plays a big role. At Draw Architecture, our cost of loft conversion calculator gives precise cost estimates by combining all of these variables to help you understand where your money will go.

Try Our Loft Conversion Cost Calculator

Our free, no-obligation Loft Conversion Cost Calculator is built to give you fast and accurate estimates for your project. Whether you’re in the early stages of planning or ready to hire an architect, our tool saves time by analysing your home’s dimensions, chosen conversion type, and regional costs across the UK.

By inputting details such as property width, depth, existing loft height, and choosing whether you need features like a bathroom or dormer windows, you’ll receive a custom cost breakdown. You can also print the results, explore cost graphs, and even see expert recommendations tailored to your setup.

This isn't just a gimmick. It's built using real architectural costing models, and only from our experience at Draw Architecture, where we’ve helped hundreds of homeowners across the UK realise their lofts’ potential.

Choose Your Loft Conversion Type

Choosing the right type of loft conversion depends on your house type and budget. Velux conversions are the least expensive because they don’t alter the roof shape, making them ideal for homes with sufficient head height.

A Dormer loft extension, one of the most common choices, adds vertical walls and a flat roof to increase usable space. Hip-to-gable conversions are perfect for semi-detached homes, extending the roofline to create more room. Mansard conversions are the most extensive and expensive, but add maximum floor space and are ideal for terraced homes in urban areas.

With our calculator, you can select the conversion type and instantly see how your choice impacts your loft conversion cost UK.

Enter Property Dimensions

Accurate measurements are crucial to estimating the cost of a loft conversion. When you enter your property's width, depth, and existing loft height, our tool calculates the total floor area and assesses structural feasibility. Taller lofts might need fewer structural alterations, reducing costs, whereas smaller, shallower lofts could require raising the roof.

This stage also helps decide whether you’ll need planning permission or can proceed under Permitted Development, something we specialise in at Draw Architecture. These details feed directly into the final estimate, making your loft conversion cost calculator result precise and useful for budgeting.

Select Key Features

Your conversion cost will also depend on the internal features you choose. Will you add a bathroom or a shower room? How many roof windows or dormer windows do you want? Do you want high-end specifications, or are you after a more standard finish?

Each choice affects labour and material costs. A bathroom adds plumbing, ventilation, and electrical requirements. More windows mean more structural adjustments. By including these features in the calculator, you’ll receive a realistic cost tailored to your preferences. This transparency helps you make decisions with confidence, guided by our professional insights at Draw Architecture.

Regional Adjustment (UK Areas)

Loft conversion costs can vary by region. For instance, London and the South East typically see higher labour and material costs than the North West or Wales. That’s why our loft conversion cost calculator asks where you live.

We’ve built region-specific data into our tool to ensure you’re seeing prices reflective of your area. Whether you’re in Greater Manchester, Bristol, Glasgow, or Surrey, we adjust your quote to reflect the most recent trends and costs.

This location-based approach makes the tool especially helpful if you're comparing prices or seeking planning help with a local architect like Draw Architecture.

View Cost Summary & Graph

Once you've filled in your details, you'll receive a full cost summary along with a visual cost breakdown chart. This graph shows where the money goes: labour, materials, fittings, windows, structural alterations, VAT, etc.

We also provide a clear disclaimer that the estimate is based on current market conditions and doesn't include certain site-specific factors. You’ll be able to print or save your results to discuss with your contractor or architect.

This data-driven approach provides far more clarity than a simple quote range. At Draw Architecture, we believe informed homeowners make smarter renovation decisions.

Recommendations Based on Your Inputs

After your estimate, our tool offers tailored recommendations to help you optimise your design and cost. If your loft is shallow, we might suggest adding a dormer instead of raising the roof. If you’re in a high-cost area, we might recommend alternative materials or standard finishes.

You’ll also see ideas for maximising head height, creating extra storage, and even increasing resale value through better layout planning. All advice is based on our UK-specific architectural expertise.

Our goal at Draw Architecture is not just to design beautiful spaces, but to help clients balance cost, functionality, and aesthetics. These recommendations are a small part of that bigger vision.

What Type of Loft Conversion is Right for You?

With so many options, choosing the right conversion can be overwhelming. Our experts at Draw Architecture help clients find the perfect fit based on home layout, local planning restrictions, and budget.

If you have a semi-detached house, a hip-to-gable is ideal. Terraced homes often suit dormer or mansard conversions. For homes with high existing rooflines, a simple Velux conversion may suffice.

The right choice depends not just on space, but on how you plan to use it , a bedroom with ensuite, a home office, or a studio flat. Our calculator guides you through these choices step by step.

Dormer Loft Conversions

A dormer loft extension is the most common and versatile type. It involves extending the roof vertically to create more headroom and usable space. Dormers are ideal for adding bedrooms, bathrooms, or home offices. They're usually permitted under Permitted Development rights and offer good value for money.

Dormer conversions typically cost between £30,000 and £60,000, depending on size and finish. The added floor area and light make them one of the most cost-effective upgrades. Our loft conversion cost calculator makes it easy to compare dormer vs. other types based on your home.

Hip-to-Gable

Popular in semi-detached and detached houses, a hip-to-gable conversion extends the side sloping roof into a vertical gable wall. This significantly increases floor space and allows for full-width rear dormers.

These conversions are more complex than Velux or dormer types and usually cost between £40,000 and £65,000. Planning permission may be required, depending on your location.

At Draw Architecture, we regularly carry out hip-to-gable conversions and can advise on whether your home qualifies for this type of extension.

Mansard

If you’re looking for maximum space, a mansard loft conversion is the way to go. This involves raising the party walls and altering the slope of the roof to create almost a full additional storey. It’s often seen in London townhouses and period properties.

Because of the structural work involved, mansard conversions are the most expensive, ranging from £50,000 to £85,000. They also typically require planning permission. Our team at Draw Architecture can help navigate approvals and create stunning, high-value designs.

L-Shape

An L-shaped dormer is ideal for Victorian terraced homes with rear extensions. It combines a main rear dormer with a smaller one over the extension, forming an “L” shape.

This layout offers fantastic flexibility, great for adding two bedrooms or a bedroom and bathroom. Costs generally start at £45,000 and go up to £75,000, depending on finish and structural complexity.

Use our cost of loft conversion calculator to see how much you’d pay for an L-shaped option in your region.

Velux

If your existing loft already has good height and structure, a Velux conversion (or rooflight conversion) could be the simplest and most affordable option. It involves adding windows to the existing roofline without altering the structure.

This keeps costs low, typically between £15,000 and £25,000. It’s perfect for home offices, guest bedrooms, or creative studios. Plus, planning permission is rarely required.

Use our loft conversion cost calculator to see how little it could take to bring new life to your loft.

Why Use Our Loft Conversion Calculator?

Quick & Free

Our Loft Conversion Cost Calculator is completely free to use and requires no sign-up or account. You can get a detailed, tailored estimate in under 60 seconds. It’s fast, intuitive, and perfect whether you’re just exploring ideas or actively budgeting your renovation. Unlike many online tools, our calculator doesn’t hide prices or demand your email first; it's fully transparent from the first click. With Draw Architecture, you get immediate, reliable guidance without the sales pressure.

Designed by Architecture Experts

What makes our calculator stand out is the expertise behind it. Developed by the planning and design professionals at Draw Architecture, this tool reflects years of real-world architectural experience across the UK. Every formula, cost range, and logic path is based on practical knowledge of how loft conversions work, from feasibility studies to full planning applications. It's not a generic estimator; it's crafted by the people who design lofts every day.

Based on Real Project Data

We’ve built the calculator using actual costings from recent loft conversion projects across the UK. This includes everything from dormer loft extension costs in suburban homes to mansard conversions in London terraces. The estimates include region-specific data, labour rates, and material prices, offering far more accuracy than typical online tools. At Draw Architecture, we regularly update the calculator to ensure it reflects evolving construction and design costs in today’s UK housing market.

What Happens After the Estimate?

Book a Consultation

Once you’ve used our loft conversion cost calculator, the next step is to discuss your project with a member of our team. We offer free initial consultations where we can explore your requirements, answer your questions, and assess feasibility.

👉 Schedule a free consultation with our architecture team

Whether you want to move ahead quickly or just explore your options, we’re here to help.

Get Planning Support

Navigating UK planning permission and building regulations can be overwhelming. At Draw Architecture, we provide full planning support, including pre-application advice, drawing submission, and communication with your local council. We specialise in loft conversions and understand what different councils expect, especially for tricky projects like mansard extensions or properties in conservation areas. Our team will ensure your application is submitted correctly, saving you time and hassle.

Design & Build Services

We don’t just stop at planning; our architectural design and project management services guide you from the initial concept through to build. This includes producing detailed architectural drawings, obtaining building control approval, and even managing contractor tendering. Whether you're planning a hip-to-gable conversion, a Velux design, or a dormer extension, we’re ready to help you achieve it with precision and style. Learn more on our Services page.

FAQs – Loft Conversion Costs & Calculator

How accurate is this calculator?

Our calculator offers a close estimate based on real UK project data and architectural insights. While it can't replace a formal survey or quote, it gives a realistic starting point. Final prices may vary based on site-specific challenges, materials chosen, and contractor rates.

Is VAT included in the estimate?

Yes, all estimates generated by the Loft Conversion Cost Calculator include 20% VAT. This ensures you're getting a true picture of what the conversion will cost, including tax implications, which many estimators skip.

Do I need planning permission for my conversion?

Not always. Many loft conversions fall under Permitted Development Rights, particularly those with Velux windows and some dormer types. However, if you're planning a mansard or hip-to-gable conversion, or live in a conservation area, you may need full planning permission. We can help you confirm during a consultation.

Can I use this for bungalow loft conversions?

Absolutely. Bungalows are perfect for loft conversions due to their roof structure and footprint. Our calculator accommodates single-storey homes and helps you explore the cost of loft conversion UK estimates for bungalows with bathrooms, dormers, and more.

What if I have a chimney or sloped ceilings?

Our calculator assumes a typical roof structure. Chimneys, sloped ceilings, or unusual layouts may affect feasibility and cost. In such cases, a custom consultation is advised so we can assess structural changes and incorporate them into the plan.

Get Your Loft Conversion Started Today

Your loft has more potential than you might think. It can be a serene bedroom, a private office, or a stylish guest suite, and it all starts with the right estimate.

Use our Loft Conversion Cost Calculator to explore your project now, and book a call with one of our experienced architectural designers.

👉 Book your free consultation now

At Draw Architecture, we bring design clarity, cost transparency, and planning confidence to every project. Let’s unlock your loft’s full potential, together.

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