Thinking about converting your loft this year? The first question almost everyone asks is the same one: what is it actually going to cost? In 2026, a loft conversion typically falls somewhere between £35,000 and £65,000, depending on the type. At Designed to Build, a rooflight conversion averages around £35,000 and a larger hip-to-gable around £65,000, with a popular rear dormer sitting around £45,000 in the middle. The range is wide because a “loft conversion” can mean anything from a few rooflights in an existing roof to a full mansard that rebuilds the entire roof structure.
This guide breaks down realistic 2026 prices by conversion type, explains what actually drives the cost up or down, covers the professional fees people forget to budget for, and gives you regional pricing for Yorkshire and the North. By the end, you will know roughly what your project should cost before you speak to a single builder.
Average Loft Conversion Cost in 2026
For a typical conversion, most of our customers spend somewhere between £35,000 and £65,000 in 2026, with a popular rear dormer averaging around £45,000.
Costs have risen steadily over the past few years on the back of material and labour inflation, so figures from older guides tend to undersell what a project costs today. The numbers below reflect 2026 rates for a standard specification: structure, staircase, insulation, windows, plastering, and a basic internal finish.
It is worth saying upfront that the single biggest factor is the type of conversion you choose. A simple rooflight job and a full mansard are both called loft conversions, but they involve very different amounts of work, and the price reflects that.
Loft Conversion Cost by Type
The conversion type is the biggest lever on your final bill. Here is a quick comparison of the four main types in 2026, followed by a closer look at each.
| Conversion type | Average cost (Designed to Build) | Build time | Best for |
|---|---|---|---|
| Velux / rooflight | around £35,000 | 4 – 6 weeks | Lofts with enough existing head height |
| Dormer | around £45,000 | 6 – 10 weeks | Most semi-detached & terraced homes |
| Mansard | around £60,000 | 12+ weeks | Maximum space; period & terraced homes |
| Hip-to-gable | around £65,000 | 10 – 14 weeks | Homes with a hipped (side-sloping) roof |
These are typical average prices for our completed projects and exclude an en-suite (around £5,000 extra). Every loft is different, so the only way to get a firm figure is a site visit. Get a free quote.
Velux (Rooflight) Conversion Cost
A Velux or rooflight conversion is the cheapest option. At Designed to Build, our rooflight conversions average around £35,000.
This type makes minimal changes to the roof. Windows are set into the existing roofline, and the work focuses on floor strengthening, insulation, plasterboarding, and a new staircase. Because there are no major structural alterations and the build time is short (usually four to six weeks), it sits at the bottom of the price range.
A rooflight conversion suits homes that already have enough head height in the loft and do not need extra floor space carved out of the roof. If your attic is tall enough to stand up in comfortably, this is often the most cost-effective route. Every loft is different, so get a free quote for a price based on your home.
Dormer Conversion Cost
A dormer conversion is the most popular choice for UK homes. At Designed to Build, our dormer conversions average around £45,000.
A dormer extends the roof outwards to create extra headroom and floor space, usually at the rear of the property. This is what most people picture when they imagine a loft bedroom: a proper room with full standing height, a window that looks out rather than up, and space for a wardrobe or even an en-suite.
The trade-off for that extra space is more structural work and a longer build, usually six to ten weeks. For most semi-detached and terraced houses, a rear dormer hits the sweet spot between cost and usable space. Get a free quote to see what a dormer would cost for your property.
Hip-to-Gable Conversion Cost
A hip-to-gable conversion is one of the larger jobs. At Designed to Build, hip-to-gable conversions average around £65,000.
This type works on properties with a hipped roof (one that slopes on the side as well as the front and back). The sloping side is rebuilt as a vertical gable wall, which dramatically increases the internal volume. It is often combined with a rear dormer for maximum space.
Because it involves rebuilding part of the roof structure, it takes longer (around ten to fourteen weeks) and costs more than a standard dormer. It suits detached and semi-detached homes with hipped roofs where a simple dormer would not free up enough usable floor area.
Mansard Conversion Cost
A mansard is the most spacious option, creating a full new storey. At Designed to Build, mansard conversions average around £60,000.
A mansard replaces the entire roof slope with a near-vertical wall, creating a full new storey with maximum floor space and head height. It usually requires planning permission and is common on period and terraced properties, particularly in conservation areas where the design needs to match the existing street.
It is one of the biggest jobs, both in cost and in disruption, but it also delivers the most room. If you want a full additional floor rather than a single bedroom, a mansard is the way to get it. Get a free quote for a price tailored to your home.
What Affects the Cost of a Loft Conversion
Two conversions of the same type can come in at very different prices. These are the factors that move the number up or down.
Size and Layout
Bigger lofts cost more in absolute terms, but the price per square metre often drops as the project gets larger because the fixed costs (staircase, structural design, scaffolding) are spread across more space. A 50m² conversion will not cost twice as much as a 25m² one.
Structural Work Required
Older roofs frequently need more strengthening than expected. Builders often adjust their figures after inspecting the loft, because the steelwork and floor reinforcement needed to carry the new load can only be confirmed once they see what they are working with.
Adding an En-Suite
A bathroom is the most common add-on. At Designed to Build, adding an en-suite costs around £5,000, covering the plumbing, waterproofing, and fittings involved.
Finish and Specification
Decorating, flooring, and built-in storage are the items that quietly push budgets over. They are easy to underestimate at the planning stage and tend to add more than people expect, so it pays to decide on your finish early rather than treating it as an afterthought.
Location
Where you live has a major impact. London and the South East run roughly 15% to 40% more than the North for the same job, which is why regional figures matter when you are budgeting.
Loft Conversion Costs in Yorkshire and the North
If you are in South Yorkshire, Leeds, or Manchester, you are on the more affordable end of the UK scale. Northern build costs typically run below the national average and well below London prices.
As a guide for 2026, our dormer conversions across the Sheffield, Leeds, and Manchester areas average around £45,000, with simpler rooflight jobs starting lower and larger hip-to-gable and mansard projects costing more. For the same specification, you generally get more for your money in the North than almost anywhere else in England.
These are guide figures rather than quotes. The only way to know what your specific roof will cost is a site visit, because head height, roof structure, and access all change the numbers. If you are local to us, our loft conversions in Sheffield and South Yorkshire page covers exactly what we do and where we work.
Don’t Forget the Professional Fees
The headline build cost is not the whole picture. Every loft conversion involves professional and statutory fees that are easy to overlook when you are comparing builder quotes.
Structural Engineer
A structural engineer is needed to specify the steelwork and certify the floor loading. Budget £400 to £800 for a standard conversion. Steel beam work is a job in its own right; our RSJ and steel beam installation service explains what is involved.
Building Regulations
Every loft conversion needs Building Regulations approval, with no exceptions. Local authority fees usually run £500 to £900, and your builder will typically arrange the inspections through the build.
Planning Permission
Many conversions fall under permitted development and do not need full planning permission. If yours does (mansards and some larger dormers often do), the planning application fee in England is around £258 in 2026.
Architectural Drawings
You will need drawings for both Building Regulations and any planning application. Costs vary, but a fixed-price drawing package removes the uncertainty and is worth asking about upfront.
Across all of these, professional fees commonly add £6,000 to £15,000 to a project once full design-and-build management is included, so factor them in from the start rather than treating them as extras.
Is a Loft Conversion Worth It in 2026?
For most homeowners, yes. A loft conversion is consistently one of the highest-return home improvements in the UK because you add a full extra room without losing garden space or extending your footprint.
Most conversions add 15% to 20% to a property’s value, and an extra bedroom with a bathroom is the single highest-value addition you can make to a typical UK house. One important condition: the value is only realised at sale if the conversion has a Building Control completion certificate, so never let a builder skip the sign-off.
Compared with the cost and upheaval of moving house, converting the space you already own is often the smarter financial move, especially in a market where moving costs (stamp duty, agent fees, legal fees) can run into tens of thousands on their own. If a loft will not give you the space you need, a house extension may be the better route, and the same design-and-build principles apply.
How to Get an Accurate Loft Conversion Quote
Online guides give you a realistic range, but they cannot account for your specific roof. The figures here are a starting point for budgeting, not a substitute for a proper assessment.
To get a firm price, you need a builder to inspect your loft and confirm the head height, the structural work required, and the layout that suits your property. From there, a fixed design-and-build quote (one that bundles the design, structural calculations, and project management into a single agreed price) gives you the clearest picture and the fewest surprises once work begins.
If you are planning a loft conversion in Sheffield, Leeds, Manchester, or anywhere across South Yorkshire, the best next step is a no-obligation site visit. We will assess your roof, talk through the right conversion type for your home and budget, and give you a clear, fixed quote with no guesswork.
Loft Conversion Cost FAQs
How much does a loft conversion cost in the UK in 2026?
In 2026 a UK loft conversion typically costs between £35,000 and £65,000 depending on the type. At Designed to Build, a rooflight conversion averages around £35,000, a dormer around £45,000, a mansard around £60,000 and a hip-to-gable around £65,000. Every project is priced individually after a site visit.
What is the cheapest type of loft conversion?
A Velux or rooflight conversion is the cheapest, averaging around £35,000 at Designed to Build. It makes minimal changes to the roof structure and has the shortest build time, so it sits at the bottom of the price range.
How much does a loft conversion cost in Sheffield, Leeds or Manchester?
Northern build costs run below the UK average. At Designed to Build, a dormer conversion across the Sheffield, Leeds and Manchester areas averages around £45,000, with rooflight jobs lower and hip-to-gable or mansard projects higher.
Does a loft conversion add value to a property?
Yes. Most loft conversions add 15% to 20% to a property’s value, and an extra bedroom with a bathroom is the single highest-value addition for a typical UK house. The value is only realised at sale if the conversion has a Building Control completion certificate.
Do I need planning permission for a loft conversion?
Many loft conversions fall under permitted development and do not need full planning permission. Mansards and some larger dormers often do. Every loft conversion, however, needs Building Regulations approval with no exceptions.
Ready to find out what your loft conversion would cost? Get a free, no-obligation quote and site visit.