How much does a loft conversion cost in the UK in 2026?
The guide ranges run from £32,000 for a rooflight conversion. A large mansard can reach £105,000 before separate project costs.
| Conversion type | Indicative contractor price | What the price covers |
|---|---|---|
| Rooflight conversion | £32,000–£45,000 | A 20–30 m² completed room within the existing roof shape |
| Rear dormer conversion | £55,000–£70,000 | A 25–35 m² rear dormer with standard internal finishes |
| Hip-to-gable with rear dormer | £65,000–£90,000 | Both roof alterations across roughly 30–40 m² |
| Mansard conversion | £80,000–£105,000 | Substantial roof reconstruction across roughly 30–40 m² |
These are budgeting estimates from published cost guides, not LoftCompare customer quote averages. The upper hip-to-gable figure reflects larger projects near 40 m².
Every range assumes a compliant habitable room and standard materials. The price covers the staircase, insulation, electrics, heating, plastering and basic joinery.
The ranges exclude separately hired designers, approvals and party wall surveyors. They also exclude an en suite, premium finishes, contingency and major hidden repairs.
London costs and difficult access can push prices beyond these ranges. So can raising the roof to create sufficient headroom.
Loft conversion costs by type
Conversion type affects cost because each option changes the roof differently. The cheapest workable design should still provide enough standing space.
Rooflight loft conversion cost
A rooflight conversion costs around £32,000 to £45,000 including VAT. It keeps the existing roof shape and avoids a large extension.
The loft needs enough existing headroom and a workable staircase position. Low ridges can make this option poor value or completely impractical.
The existing ceiling joists will normally need replacement or strengthening. A structural engineer must design the new habitable floor.
VELUX is one roof-window brand, although people often use the name generically. Compare window specifications in our rooflight and VELUX cost guide.
Dormer loft conversion cost
A standard rear dormer costs around £55,000 to £70,000 including VAT. This assumes one completed room without an en-suite bathroom.
The dormer creates headroom without rebuilding the entire roof. Its width, cladding, glazing and roof junctions affect the final price.
An L-shaped dormer needs more structure and weatherproofing than a simple rear dormer. It can therefore exceed the guide range.
Our dormer loft conversion cost guide explains how size and specification change the budget.
Hip-to-gable loft conversion cost
A hip-to-gable conversion with a rear dormer costs £65,000 to £90,000. This range covers both roof alterations, not only the new gable.
Replacing the sloping side roof adds structural and roofing work. Larger projects near 40 m² explain the upper end of the range.
This design often suits semi-detached and end-of-terrace houses. Attached properties may also need a party wall agreement.
Surveyor fees only arise when the proposed work and neighbour response require them. The Party Wall etc. Act applies in England and Wales.
See our hip-to-gable cost guide for simpler gables and combined designs.
Mansard loft conversion cost
A mansard conversion costs around £80,000 to £105,000 including VAT. It rebuilds much of one roof slope to create standing space.
This work needs detailed structural design and substantial weather protection. Urban access and heritage requirements can increase costs further.
Mansards often need planning permission for a loft conversion. Local design restrictions may also limit the proposal.
Our mansard loft conversion cost guide covers layout and structural choices in detail.
How do modular and shell-only loft conversion prices work?
Modular and shell-only describe procurement choices, not separate roof designs. Their quotations cannot fairly sit beside completed roof-type prices.
A modular loft conversion arrives in factory-made sections. The quote should define manufacture, delivery, lifting, roof removal and service connections.
Some packages include standard crane lifting but exclude difficult access arrangements. Preparing crane access or moving overhead services can add substantial costs.
A shell-only conversion stops before full internal completion. However, each contractor defines the shell stage differently.
Some shell quotes include stairs and insulation, while others exclude both. Services, fire doors, plastering and decoration may also remain unfinished.
No national guide range appears here because these scopes vary too widely. Request a project-specific price against a written list of inclusions.
What is included in a loft conversion price?
A completed-build quotation should cover a usable room meeting Building Regulations requirements. However, builders define completion differently.
Approval routes and technical standards differ across the UK. Confirm the local requirements before relying on national guidance.
Work normally included in a completed conversion
A clear contractor quotation should identify these core items:
- Structural floor, supporting steelwork and agreed roof alterations
- Rooflights, dormer windows and external weatherproof finishes
- Roof, wall and floor insulation within the converted area
- Internal partitions, plasterboard and plastered wall finishes
- Standard sockets, lighting, smoke alarms and heating
- Staircase, balustrades and the required structural opening
- Agreed fire-safety upgrades along the escape route
- Basic doors, skirting, architraves and internal joinery
Decoration and floor coverings do not always form part of completion. Ask whether the builder includes both within the fixed price.
The staircase also affects rooms below the loft. Check who pays for making good the landing or bedroom.
Costs commonly excluded from advertised prices
Headline prices can leave several important costs outside the contract:
- VAT when the quotation shows a price before tax
- Architect, technologist and structural engineer fees
- Planning, lawful development and building control charges
- Conditional party wall surveyor fees for attached properties
- Temporary roofing, licences and parking suspensions
- En-suite bathroom fittings, drainage and service upgrades
- Bespoke storage, premium glazing and upgraded decoration
- Repairs discovered after the existing roof is opened
Ask whether bathroom figures include fittings or installation only. Drainage and service routes still need planning before construction begins.
Does a loft conversion quote include VAT?
Some quotations include VAT, while others show a net price. The written quotation must state its tax basis clearly.
Most existing-home building work carries 20% VAT from VAT-registered contractors. A £55,000 net quote would then become £66,000.
Do not add 20% blindly to every project fee. Statutory charges and professional invoices may follow different tax treatment.
Compare final payable totals from each provider. Mixing gross and net prices makes comparisons misleading.
Loft conversion cost breakdown
The largest construction costs normally sit within the main contractor price. Steelwork, floor structure and dormer work often overlap within one package.
Avoid adding isolated component figures to the headline conversion range. That approach can count the same labour and materials twice.
The following allowances help identify common separate or clearly defined costs. They are not a complete project total.
| Cost item | Budgeting allowance | Scope to check |
|---|---|---|
| Planning or permitted development drawings | £1,200–£3,000 | Survey, design, application drawings and included revisions |
| Planning and technical drawing package | £3,000–£6,000 | Planning plus Building Regulations information, without project supervision |
| Structural engineering | £840–£2,160 | Calculations, drawings, revisions and site visits |
| Loft conversion stairs | £4,500–£12,000 | Staircase, balustrade, structural opening and making good |
| En-suite bathroom | £5,000–£12,000 | Fittings, plumbing, drainage, waterproofing, tiling and ventilation |
| Scaffolding | £840–£9,600 | Elevations, hire period, obstacle bridging and any temporary roof |
| Building control | Provider quotation | Application route, plan checking, inspections and completion certificate |
These allowances show final homeowner costs where 20% VAT applies. Confirm each provider's VAT treatment before adding their figure.
An en-suite allowance excludes major boiler or hot-water cylinder upgrades. Those changes need a separate heating assessment.
Our detailed guides explain architect fees, loft conversion stairs and scaffolding costs.
Example loft conversion budgets
These constructed examples show how a full budget can build up. They are illustrations, not recorded homeowner quotations.
Every figure includes VAT where applicable and standard internal finishes. Grouped finishing costs include basic flooring, waste removal and contractor overheads.
They also include reasonable making good in rooms affected downstairs. Party wall fees, premium upgrades and major hidden repairs remain excluded.
Each example uses a 10% contingency to show the calculation. A 15% allowance may suit older or less certain structures.
Example 1: 25 m² rooflight loft conversion
This example assumes a traditional cut roof with sufficient head height. It creates one bedroom without a bathroom.
| Budget item | Homeowner cost |
|---|---|
| Design and structural engineering | £2,400 |
| Structural floor and steelwork | £10,000 |
| Rooflights and local roof work | £4,000 |
| Staircase and structural opening | £4,500 |
| Insulation, partitions and plastering | £7,500 |
| Electrics, heating, fire work, joinery and finishing | £5,500 |
| Scaffolding and roof access | £1,500 |
| Building control and compliance charges | £800 |
| Subtotal including VAT where applicable | £36,200 |
| Contingency at 10% | £3,620 |
| Illustrative budget including contingency | £39,820 |
The contractor portion remains within the rooflight guide range. A low ridge or complex floor structure would increase it.
Example 2: 30 m² rear dormer loft conversion
This example creates one bedroom without an en suite. It assumes normal access and a standard rear dormer.
| Budget item | Homeowner cost |
|---|---|
| Design and structural engineering | £3,600 |
| Structural floor and steelwork | £13,500 |
| Dormer, roofing and windows | £17,000 |
| Staircase and structural opening | £5,000 |
| Insulation, partitions and plastering | £7,500 |
| Electrics, heating, fire work, joinery and finishing | £5,000 |
| Scaffolding | £3,000 |
| Building control and compliance charges | £900 |
| Subtotal including VAT where applicable | £55,500 |
| Contingency at 10% | £5,550 |
| Illustrative budget including contingency | £61,050 |
The completed homeowner budget reaches £61,050 after contingency. An en suite could add £5,000 to £12,000.
Example 3: 35 m² hip-to-gable and rear dormer
This example assumes a semi-detached house with a hipped roof. It includes broader steelwork but no en suite.
| Budget item | Homeowner cost |
|---|---|
| Design and structural engineering | £4,500 |
| Structural floor and steelwork | £16,000 |
| Hip-to-gable, dormer, roofing and windows | £25,000 |
| Staircase and structural opening | £5,500 |
| Insulation, partitions and plastering | £8,000 |
| Electrics, heating, fire work, joinery and finishing | £5,000 |
| Scaffolding and temporary weather protection | £4,500 |
| Building control and compliance charges | £1,000 |
| Subtotal including VAT where applicable | £69,500 |
| Contingency at 10% | £6,950 |
| Illustrative budget including contingency | £76,450 |
The completed homeowner budget reaches £76,450 after contingency. Roof raising or difficult access would increase it.
How much does a loft conversion cost per m²?
Allow about £1,300 to £3,000 per m² for early comparisons. This is calculated from the guide ranges and their midpoint sizes.
At 25 m², the rooflight range gives £1,280 to £1,800 per m². A 30 m² dormer gives about £1,830 to £2,330.
At 35 m², hip-to-gable costs equal roughly £1,860 to £2,570 per m². The mansard range gives about £2,290 to £3,000.
These figures are calculations, not independently measured market rates. Smaller projects can exceed them because fixed costs remain similar.
For consistency, area means finished internal floor space after conversion. It includes low-eaves floors but excludes the staircase opening.
Builders may use another measurement method within their quotation. Confirm the measured area before comparing square-metre prices.
Low-eaves floor can make a unit rate look attractive. However, limited standing space may offer little practical value.
How does property type affect loft conversion costs?
Property type affects roof shape, access and shared structures. The proposed conversion still determines the starting price.
A mid-terraced house often suits a rear or L-shaped dormer. Restricted access and two shared walls can add costs.
End-of-terrace and semi-detached houses may suit hip-to-gable designs. The side roof alteration places them above a simple dormer budget.
A detached house avoids a shared party wall. Larger roof spans and more external area can still increase costs.
A bungalow conversion needs careful classification before budgeting. A dormer within the roof differs greatly from a full roof lift.
Use the relevant roof-type range for an ordinary bungalow dormer. Seek a project-specific quotation for roof lifts or new upper storeys.
What affects the final cost of a loft conversion?
The roof and structural solution drive cost before decorative choices. Early feasibility checks can prevent wasted design spending.
Roof structure and available head height
Traditional cut roofs often provide clearer internal space. Trussed roofs need engineered changes before removing any webs.
Low ridges can require ceiling lowering or roof raising. Both options add structural work, disruption and cost.
Check minimum loft height considerations before relying on floor area. A large but low loft may offer poor value.
Conversion size and structural complexity
Larger conversions need more labour and materials. Structural complexity can matter more than modest floor-area increases.
Chimneys, unusual spans and previous alterations complicate the steelwork. Multiple dormers also create extra roof junctions.
Staircase position and room layout
The staircase needs enough headroom for safe use. Its position can take space from the landing or bedroom below.
Winders, split flights and bespoke balustrades cost more than simple stairs. Larger openings can need extra structural support.
Bathrooms, windows and finish level
An en-suite bathroom adds drainage, ventilation, waterproofing and fittings. Long waste-pipe routes increase labour and design risk.
Plan drainage and water supplies before construction starts. Fittings can be selected later if the budget tightens.
Large windows and balcony systems need more structure and external work. Bespoke joinery and premium flooring remain optional upgrades.
Property access and scaffolding
Terraced access, conservatories and narrow streets can complicate deliveries. Highway scaffolding may need licences and parking suspensions.
A temporary roof can cost as much as the access scaffold. Check whether the allowance includes one before comparing quotes.
Location and regional labour costs
Labour, travel and parking costs vary across the UK. Restricted sites can raise prices independently of floor area.
London projects can exceed national ranges. Use our London loft conversion cost guide for local budgeting.
How much contingency should you allow?
Allow 10% to 15% above the payable construction budget. Use the higher figure for older or poorly surveyed roofs.
The Federation of Master Builders recommends at least 10%. It suggests 15% or more for structural work and older homes.
Loft conversions always involve structural alterations. Limited access or unclear existing work strengthens the case for 15%.
Rotten timbers and outdated wiring can appear after opening the roof. Hidden plumbing and previous alterations cause similar surprises.
Calculate contingency on the construction price after applicable VAT. Add professional and statutory fees using their actual payable totals.
Keep contingency outside the contractor's quoted price and under your control. Do not spend it on upgrades before structural completion.
How to compare loft conversion quotes
Comparable quotes need the same drawings, specification and completion standard. A lower price can contain more exclusions.
Check every quotation answers these points:
- Does the total include VAT at the stated rate?
- Are design drawings and structural calculations included?
- Does scaffolding include a temporary roof and extra hire?
- Are staircase installation and downstairs repairs included?
- Does fire work cover doors along the escape route?
- Are bathroom fittings included, or only their installation?
- Who handles ventilation, testing and completion certificates?
- Are floor finishes, decoration, waste removal and cleaning included?
- Which building control charges and responses remain separate?
- Which figures are provisional sums rather than fixed prices?
A provisional sum remains an allowance, not a fixed price. Low allowances can make one quote look artificially cheap.
Ask whether each allowance includes labour, delivery and VAT. Read every exclusion beside the drawings and specification.
Payment stages should follow visible progress. The contract should explain deposits, variations, completion and defect correction.
Approve every variation in writing before work continues. Each change should show its cost and programme effect.
Once the scope is clear, compare loft conversion quotes on the same basis.
How to reduce loft conversion costs
Good savings simplify the project without weakening safety or compliance. The strongest decisions happen before construction begins.
- Choose the simplest design providing enough usable standing space.
- Confirm head height and structure before commissioning detailed drawings.
- Keep bathroom drainage close to existing soil and water services.
- Use standard windows, staircase details and available finishes.
- Avoid layout changes after the structural design becomes fixed.
- Complete suitable decorating after the compliant building work finishes.
Never reduce structural, insulation or fire specifications to save money. Unsafe work can prevent approval and harm resale.
How LoftCompare calculates its cost estimates
These are budgeting estimates drawn from published cost guides. They are not averages calculated from LoftCompare customer quotations.
We used the September 2026 Estiquote cost guide as the main benchmark. Current Checkatrade and Chat to Your Builder figures provided boundary checks.
The Homebuilding mansard guide provided an additional specialist comparison.
Published sources use different sizes, regions and completion standards. Some also separate stairs, fees or contingency from construction costs.
We did not assume VAT where a source left its basis unclear. We also avoided treating repeated or synthesised figures as independent evidence.
The headline ranges use a defined completed-room specification. They include contractor VAT where applicable, but exclude separately hired professional fees.
Prices need reviewing when labour, tax or regulations change materially. Homeowners should still compare written quotations for their own property.
Once you have a clear specification, compare quotations from local loft specialists.