How Much Does a Loft Conversion Cost in 2026?
London Loft Conversion Price Guide
If your home is beginning to feel short on space, moving is not always the only solution. A loft conversion can create an additional bedroom, bathroom, office or living area without increasing the footprint of your property.
For many homes, converting the loft can also be a more practical alternative to constructing a large extension, particularly where garden space is limited.
The question most homeowners ask first is simple:
How much does a loft conversion actually cost in 2026?
There is no single figure. The final cost depends on the existing roof structure, property size, type of conversion, structural requirements, access, location and the standard of finish.
As a broad guide, a typical loft conversion in the UK in 2026 may cost around £50,000, while projects can range from approximately £25,000 to £80,000+.
Larger, structurally complex or high-specification conversions in London and the South East can exceed this considerably.
The type of conversion is one of the biggest factors affecting the overall project cost.
Loft Conversion Type | Typical 2026 Cost |
Velux Conversion | £22,500–£30,000 |
Shell Loft Conversion | £22,500–£37,500 |
Dormer Loft Conversion | £40,000–£60,000 |
Hip-to-Gable Conversion | £50,000–£70,000 |
Mansard Loft Conversion | £50,000–£80,000 |
Modular Loft Conversion | £30,000–£60,000 |
Bungalow Loft Conversion | £62,500–£87,500+ |
These figures are indicative budgeting ranges rather than quotations. The final cost will depend on the property, design, specification and location.
Velux Loft Conversion
A rooflight conversion is generally one of the simplest ways of converting a loft.
Rather than significantly changing the external shape of the roof, roof windows are installed into the existing roof slopes and the internal space is upgraded to provide habitable accommodation.
Typical cost: £22,500–£30,000
This option works particularly well where the loft already has sufficient headroom and usable floor area.
Because relatively little alteration is made to the external roof structure, construction can also be quicker and less disruptive than more extensive conversion types.
The main limitation is that the amount of usable space remains largely dictated by the existing roof shape.
Dormer Loft Conversion
A dormer conversion is one of the most common loft conversion types in the UK.
The dormer extends outward from the existing roof slope, creating greater headroom and significantly increasing the amount of usable internal floor space.
Typical cost: £40,000–£60,000+
A well-designed dormer conversion can potentially create space for:
A new bedroom
An ensuite bathroom
A home office
Built-in wardrobes
Additional storage
A bedroom and bathroom combination
For many terraced and semi-detached properties, a rear dormer provides a good balance between construction complexity and additional usable space.
Projects in London, particularly those incorporating high-end finishes, bespoke joinery or substantial structural alterations, can cost considerably more than the national average.
Hip-to-Gable Loft Conversion
Hip-to-gable conversions are commonly undertaken on semi-detached, detached and end-of-terrace houses with hipped roofs.
The sloping side of the existing roof is extended vertically to form a new gable wall.
Typical cost: £50,000–£70,000+
This can dramatically increase the width and usable headroom within the loft.
Hip-to-gable projects frequently incorporate a rear dormer as well, allowing significantly more internal space to be created.
Because the existing roof structure is substantially altered, structural steelwork and more extensive roof reconstruction will normally be required.
Mansard Loft Conversion
A mansard conversion involves much greater alteration to the original roof.
The roof is effectively reconstructed with steep external faces and a flatter upper section, producing an interior that can feel much closer to a conventional additional storey.
Typical cost: £50,000–£80,000+
Mansard conversions can provide a substantial increase in usable floor area, but the amount of structural and roofing work involved makes them one of the more expensive conversion types.
Larger or higher-specification mansard projects in London can exceed these figures significantly.
Bungalow Loft Conversion
Bungalows can offer particularly good opportunities for loft conversions because the roof frequently covers a relatively large footprint.
A successful conversion can effectively transform a single-storey home into a two-storey property.
Typical cost: £62,500–£87,500+
The cost is often higher than that of a conventional house conversion because considerably more floor area may be created.
The existing roof structure, staircase position and amount of structural reinforcement required will all influence the final cost.
Shell Loft Conversion
A shell conversion can be suitable where the homeowner wants a contractor to complete the principal structural and weatherproofing works while arranging some of the internal finishing separately.
Typical cost: £22,500–£37,500
Depending on the agreed specification, a shell package may include:
Structural steelwork
New floor structure
Dormer construction
Roof alterations
External cladding
Windows
Weatherproofing
Staircase opening
Internal decoration, flooring, joinery and some building services can then be completed separately.
When comparing shell quotations, it is particularly important to establish exactly what is included and excluded.
Modular Loft Conversion
Modular conversions involve manufacturing a significant proportion of the new loft structure away from the property before transporting it to site for installation.
Typical cost: £30,000–£60,000+
Although off-site fabrication can reduce certain aspects of on-site construction, modular conversions come with their own logistical considerations.
These can include crane access, transportation, road restrictions, structural preparation and weather conditions during installation.
What Makes Up the Cost of a Loft Conversion?
The finished bedroom or bathroom is only one part of the project.
A significant proportion of the cost of a loft conversion is associated with structural, access and technical work that eventually becomes hidden behind the finished surfaces.
Scaffolding
Substantial loft conversions will normally require scaffolding to provide safe access to the roof.
Scaffolding may be required for:
Roof removal
Dormer construction
Steel installation
Roofing
Windows
External cladding
Flashings and gutters
Some projects may also require temporary roof protection.
The price can vary considerably depending on property height, access, scaffold duration and whether a temporary roof is required.
Demolition and Strip-Out
Sections of the existing roof normally have to be carefully removed before a dormer or altered roof structure can be constructed.
This creates additional costs for:
Labour
Roof strip-out
Waste removal
Skips
Temporary protection
Loading and transport
Restricted access can increase the cost where waste and materials need to be moved manually through or around the property.
Structural Engineering and Steelwork
A loft conversion is a structural alteration to the property.
The existing ceiling joists in a conventional loft were generally not designed to support a new habitable floor.
A structural engineer will therefore usually design the new load-bearing arrangement and provide structural calculations.
Steelwork may be required to support:
The new loft floor
The altered roof
The dormer
The ridge
New structural openings
The staircase area
The number and size of structural members required depends entirely on the existing building and proposed design.
New Loft Floor Structure
In most loft conversions, a completely new structural floor is installed above the existing ceiling.
This can include:
New floor joists
Engineered timber
Structural steels
Structural decking
Acoustic insulation
Fire protection
The design will depend on the width of the property, structural spans and location of supporting walls.
Dormer Construction
Once the primary floor and structural steelwork have been installed, the dormer structure can be constructed.
This typically involves:
Timber framing
Structural sheathing
Roof construction
Breather membranes
External cladding or coverings
Insulation
Windows
Internal partitions
At this stage, the shape of the new accommodation begins to become clearly visible.
Insulation and Thermal Performance
Insulation is particularly important in loft conversions because a large proportion of the new accommodation sits directly within the roof.
Insulation may be installed within:
Roof slopes
Dormer cheeks
Dormer roofs
External walls
Floors
Areas surrounding structural steel
The exact construction build-up should be designed to satisfy the applicable Building Regulations while also considering condensation risk and long-term building performance.
Staircase
A permanent staircase is required to connect the new loft with the rest of the house.
Its position can significantly affect both the loft layout and the floor below.
Costs can vary considerably between:
Standard softwood staircases
Hardwood staircases
Bespoke staircases
Timber and steel designs
Glass balustrades
Custom joinery
For this reason, the staircase should ideally be considered during the early design stages rather than after the loft layout has already been decided.
Windows and Glazing
Different conversion designs may incorporate:
Velux or other rooflights
Dormer windows
Gable windows
Juliet balconies
French doors
Bespoke aluminium glazing
Standard rooflights can be relatively straightforward, while large bespoke glazing packages can add several thousand pounds to the overall project.
Bathrooms and Plumbing
Adding an ensuite bathroom is one of the most common features of a loft conversion.
This can require:
Hot and cold water supplies
Waste pipes
Soil connections
Ventilation
Sanitaryware
Waterproofing
Tiling
Heating
Electrical works
Positioning the new bathroom relatively close to existing services can sometimes simplify the installation.
Electrical Works
The loft will normally require its own new electrical installation.
This may include:
Lighting
Socket outlets
Smoke detectors
Extractor fans
Bathroom supplies
Heating controls
Data points
Electrical certification
Architectural lighting, smart-home controls and premium fittings will increase the specification and cost.
Fire Protection
Creating another habitable floor introduces important fire-safety requirements.
Depending on the property, upgrades may be required to:
Internal doors
Stair enclosures
Floors
Ceilings
Smoke detection
Escape routes
Fire stopping
These requirements should be incorporated into the project design from the beginning.
Does a Loft Conversion Need Planning Permission?
Not always.
Many loft conversions to houses in England can potentially be undertaken under Permitted Development, provided they comply with the relevant restrictions.
Among the important limits are generally:
Up to 40m³ of additional roof space for terraced houses
Up to 50m³ for other houses
Other restrictions apply to height, materials, roof position and the design of the enlargement.
Planning permission may still be required where the project exceeds permitted development limits, the property has restricted permitted development rights, or the proposed design falls outside the relevant criteria.
Properties within conservation areas or other designated locations may also be subject to additional controls.
Does a Loft Conversion Need Building Regulations Approval?
Yes.
Planning permission and Building Regulations approval are separate matters.
Even where a loft conversion falls within Permitted Development, converting the loft into habitable accommodation will generally require Building Regulations approval.
Building Control will typically consider:
Structural stability
Floor strength
Fire safety
Staircase design
Thermal insulation
Ventilation
Electrical safety
Sound insulation
Inspections are normally carried out at different stages throughout the construction process.
How Long Does a Loft Conversion Take?
Construction time depends heavily on the type of conversion and complexity of the property.
As a broad guide:
Conversion Type | Typical Construction Period |
Velux Conversion | 4–6 weeks |
Mansard Conversion | 8–10+ weeks |
Dormer Conversion | 8–12 weeks |
Hip-to-Gable Conversion | 10–12+ weeks |
These figures generally refer to the construction period itself.
Design, structural engineering, approvals, party-wall matters, procurement and planning permission where required should be allowed for separately.
Why Do Loft Conversion Quotes Vary So Much?
Two loft conversions of a similar size can have substantially different costs.
Existing Roof Structure
A traditional cut roof can require a different construction approach from a trussed roof.
Structural Spans
Larger properties can require heavier steelwork and more complex structural solutions.
Site Access
Restricted access affects waste removal, material handling and the installation of structural steelwork.
Location
Construction costs in London and parts of the South East are generally higher due to labour, parking, access, logistics and operating costs.
Bathroom Specification
Bathrooms can range from relatively simple specifications to high-end installations incorporating premium sanitaryware, stone finishes and bespoke joinery.
Glazing
Standard rooflights cost considerably less than bespoke aluminium glazing or large Juliet balcony installations.
Bespoke Joinery
Built-in wardrobes, storage, staircases and other custom joinery can materially increase the project cost.
Condition of the Existing Property
Older buildings can reveal additional structural, roofing or building-services requirements once works begin.
Quality of Finish
There is a significant difference between a straightforward painted room and a fully detailed high-end interior.
How Much Should You Budget for a Loft Conversion in 2026?
For a relatively straightforward dormer loft conversion, an initial budget of approximately £40,000–£60,000 may be appropriate for many UK properties.
More substantial projects involving hip-to-gable alterations, large dormers, ensuite bathrooms, bespoke joinery and higher specifications can realistically move into the £60,000–£80,000+ range.
Complex projects in London can exceed these figures.
When comparing quotations, it is important to compare the scope of work, rather than simply looking at the total price.
One contractor may include structural steel, decoration, sanitaryware and flooring while another may exclude them entirely.
Is a Loft Conversion Worth It?
Where the existing property is suitable, a loft conversion can be one of the most effective ways of creating additional living accommodation without sacrificing garden space.
A conversion can provide:
Additional bedrooms
Ensuite bathrooms
Home-working space
Additional storage
Improved family accommodation
More effective use of the existing property
The quality of the structural design, insulation, waterproofing, services and internal detailing will ultimately determine how well the new accommodation performs over the long term.
For that reason, a loft conversion should be approached as a complete construction project rather than simply as a way of creating an additional room.
Frequently Asked Questions
What is the average cost of a loft conversion in the UK in 2026?
A typical loft conversion may cost approximately £40,000–£60,000, although simpler rooflight conversions can cost less and larger structural conversions can exceed £80,000.
Location, property type, roof structure and specification all influence the final figure.
How much does a dormer loft conversion cost in 2026?
A typical dormer loft conversion may cost around £40,000–£60,000+. Larger dormers, ensuite bathrooms, high-end finishes or projects in London can increase the cost substantially.
Is a loft conversion cheaper than an extension?
It can be. A loft conversion makes use of the existing roof space and does not normally require new foundations around the perimeter of the property.
However, the relative cost depends on the structural complexity, size and specification of each project.
Can I live in the house during a loft conversion?
In many cases, yes.
A significant amount of the early construction work can often be accessed externally from scaffolding. There will still be periods of noise, dust and disruption, particularly when the new staircase is installed and the loft is connected to the existing house.
Do I need an architect for a loft conversion?
Not every project requires the same professional team, but properly prepared drawings are important. More substantial conversions will also normally require structural engineering input and Building Regulations approval.
Planning input may also be required depending on the property and proposed design.
How long does a loft conversion take?
A relatively straightforward conversion may take approximately 6–12 weeks of construction, while more complex projects can take longer.
Design, approvals and planning should be considered separately from the physical building period.
Planning a Loft Conversion?
Slateriver Group undertakes residential construction, refurbishment and structural alteration projects across London, Hertfordshire and the surrounding areas.
Our approach brings together the structural, roofing, building-services and interior elements required to deliver a loft conversion as one coordinated construction project.
If you are considering converting your loft, we can review the existing property, proposed design and project requirements before developing an appropriate scope of works.
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