Loft Conversion Cost UK – 2026 Price Guide
How much does a loft conversion cost in the UK in 2026? This guide uses live pricing data across 519 UK towns to give you realistic figures for dormer, hip-to-gable and mansard conversions — with worked examples, cost factors and a free quote tool.
Do you need planning permission for this?
Most loft conversions fall under Permitted Development (up to 40m³ for terraces, 50m³ for detached). But front dormers, listed buildings, and conservation areas need full planning. 5-minute read.
Read the loft conversion planning rules →Loft Conversion Cost at a Glance
Real cost ranges from BestBuilders data across 519 UK towns. Use these as your starting benchmark — then get 3 local quotes for your exact project.
The most popular type in the UK. Creates a full-height room with vertical rear wall and flat roof. Usually includes en-suite and Velux windows to the front.
Get quotes →Extends the ridge line on hipped-roof properties to maximise floor space. Usually paired with a rear dormer. Ideal for end-of-terrace and detached homes.
Get quotes →The most spacious type — near-vertical rear wall with shallow-pitched roof. Common in London terraces and conservation areas. Usually needs planning permission.
Get quotes →The only accurate price comes from a specialist who has seen your roof. Get 3 free quotes from vetted local loft specialists.
Get free quotes →Loft Conversion Cost Summary Table (UK 2026)
| Type | National range | Typical size | Planning |
|---|---|---|---|
| Velux / rooflight only | £15,000 – £30,000 | Depends on roof pitch | Usually PD |
| Rear dormer | £30,000 – £81,000 | Typically 25–40m² | Usually PD |
| Hip-to-gable + dormer | £33,000 – £93,000 | Typically 30–50m² | Usually PD |
| Mansard | £38,000 – £113,000 | Typically 35–55m² | Usually needs PP |
PD = Permitted Development (no planning application required). PP = Full planning permission. Ranges cover basic to premium specification including en-suite. London and South East add 35–45% to the upper end.
Loft Conversion Cost by Type (2026)
Velux / Rooflight Loft Conversion
The simplest and most affordable conversion — no structural changes to the roof shape, just Velux-style roof windows inserted into the existing slope. Requires sufficient existing headroom (minimum 2.2m at ridge). Best for properties with tall, steeply pitched roofs where headroom already exists. The room will have sloped ceilings but can still be well-designed.
Rear Dormer Loft Conversion
The most popular conversion in the UK. A dormer extends from the rear roof slope to create a full-height room with a flat or pitched roof and vertical rear wall. Typically includes an en-suite bathroom and Velux windows to the front slope. Works on most property types and usually falls under Permitted Development.
Hip-to-Gable Loft Conversion
For properties with a hipped roof (slopes on all four sides), a hip-to-gable conversion extends the ridge line to create a vertical gable wall — dramatically increasing the usable floor area. Almost always paired with a rear dormer for best results. Most common on end-of-terrace and detached homes.
Mansard Loft Conversion
The most spacious and structurally complex conversion — the rear roof slope is replaced with a near-vertical wall (typically 72° pitch), creating a full-height room across the entire rear. Common in London and city centre terraces, and in conservation areas where dormers are restricted. Typically requires full planning permission and commands premium prices in London.
Worked Cost Examples (2026)
Full project budgets including staircase, en-suite, professional fees and contingency — not just the build cost.
Example 1: Rear Dormer with En-Suite (Mid-Range)
Mid-range finish. London/SE add 35–45%.
Example 2: Hip-to-Gable + Dormer, Two Bedrooms
Mid-range finish. London/SE add 35–45%.
What Affects Loft Conversion Cost?
Six factors move loft conversion budgets significantly. Understanding them helps you compare quotes accurately and avoid surprises.
🏗 Conversion type
A Velux-only conversion (no structural changes) is the cheapest. A rear dormer is mid-range. A hip-to-gable involves rebuilding part of the roof structure. A mansard requires almost complete rear roof reconstruction — significantly more expensive. The conversion type is usually dictated by your property and roof shape.
📐 Available headroom
The minimum headroom for habitable space is 2m (Building Regulations); most specialists want to see 2.2–2.4m at the ridge before excavating floor joists. Insufficient headroom means floor lowering — adding cost (£2,000–£6,000) and structural complexity. Steep-pitched Victorian roofs convert most easily; shallow modern pitches may not be suitable.
🚿 Bathroom specification
Most loft conversions include an en-suite — typically 25–30% of the overall cost. A compact shower room with budget suite costs £4,000–£7,000; a larger premium en-suite £8,000–£15,000. The cost of running new soil pipes down through the house can add £1,500–£3,000 if the route is complex.
🪜 Staircase design
Building Regulations require a fixed staircase meeting minimum width and headroom requirements — not a loft ladder. A standard straight staircase costs £2,500–£5,000 installed; a bespoke or space-saving design (alternating tread, spiral, quarter-landing) £4,000–£8,000. The staircase also involves modifying the floor below, which adds disruption and cost.
🔧 Structural complexity
Older properties with cut roofs (pre-1960s) convert more easily than modern trussed rafter roofs, which require additional steel work to create the required clear span. Party walls (on terraced houses) trigger the Party Wall Act — serving notices, and potentially appointing surveyors, adds £800–£2,500 and 1–2 months of lead time.
📍 Location & access
London and South East labour rates run 35–45% above the national average for loft conversions — above most other trades, because specialist loft firms in London command a premium. Restricted access (no scaffold run, tight urban streets, conservation area material restrictions) also adds cost. Use our local town pages for area-specific pricing.
Loft Conversion Cost by Region (2026)
| Region | Relative cost | Dormer guide range | Mansard guide range |
|---|---|---|---|
| London | Highest | £50,000 – £85,000+ | £65,000 – £115,000+ |
| South East & Home Counties | High | £40,000 – £70,000 | £52,000 – £90,000 |
| South West & Midlands | Medium | £34,000 – £58,000 | £43,000 – £75,000 |
| North of England | Medium-low | £30,000 – £52,000 | £38,000 – £68,000 |
| Scotland, Wales & NI | Medium-low | £30,000 – £50,000 | £38,000 – £65,000 |
Mid-specification ranges including en-suite. Party wall costs, professional fees and contingency are additional. Get local quotes via our town pages for accuracy.
Does a Loft Conversion Add Value?
A loft conversion is one of the highest-ROI home improvements available to UK homeowners — adding usable bedroom space without using any garden, and consistently delivering strong returns in most property markets.
Best ROI comes from conversions with proper Building Regulations completion certificates — essential for mortgage and insurance purposes and for future buyers.
How to control your loft conversion budget
Floor lowering to create headroom adds significant cost. Have a specialist assess the loft before you commit to a budget.
A straight or quarter-landing staircase is £1,500–£2,500 cheaper than bespoke designs. Space-saving stairs look stylish but add cost — decide early.
If neighbours consent promptly the process is free. Delays add months to the programme and surveyor costs escalate fast if disputes arise.
Specialists who convert 20+ lofts per year work more efficiently, know the regulations and make fewer costly errors than generalists tackling occasional loft work.
Loft conversions uncover unexpected structural issues — particularly in older properties. Never build to an absolute maximum without contingency headroom.
Get Accurate Quotes for Your Loft Conversion
Online guides give you a benchmark — but accurate pricing requires a specialist who has measured your loft, assessed your roof type and reviewed your headroom. BestBuilders matches you with up to 3 vetted local loft specialists for free.
Loft Conversion Cost FAQs
Loft Conversion Costs by Town
Each town page shows local loft conversion specialists, town-specific cost ranges, recent project examples and nearby areas. Compare 3 free quotes from vetted local specialists.