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.
Velux vs Dormer vs Hip-to-Gable vs Mansard vs L-Shape: UK 2026 Loft Comparison
The five UK loft conversion types differ in cost, planning rules, floor area gained, and which roof shapes they suit. Velux (rooflight) is cheapest but adds least usable space. Mansard delivers maximum floor area but is the most expensive and almost always needs planning permission. Below is the verified Q2 2026 comparison.
| Loft Type | UK Total Cost 2026 | Floor Area Added | Build Time | Planning | Best For |
|---|---|---|---|---|---|
| Velux / Rooflight | £25,000-40,000 | 15-25 m² | 4-6 weeks | Usually PD | Tall existing lofts, budget builds |
| Dormer (rear or side) | £30,000-65,000 | 25-40 m² | 6-10 weeks | PD typical | Most UK terraces, semis, headroom upgrade |
| Hip-to-Gable | £33,000-70,000 | 30-50 m² | 8-12 weeks | PD typical (semi/end-of-terrace) | Semi-detached + end-of-terrace with hipped roof |
| Mansard | £38,000-90,000 | 35-60 m² | 10-14 weeks | Planning required | Terraces, max floor area, London |
| L-Shape (rear dormer + side return) | £55,000-100,000 | 40-70 m² | 12-16 weeks | Planning + party-wall | Victorian terrace with side return |
| Bungalow Roof Lift | £40,000-95,000 | 40-75 m² | 10-14 weeks | Planning typical | Bungalow with adequate roof span |
Costs include structural steelwork, stairs, dormer/rooflight glazing, insulation, plastering and decoration. Bathroom add-on £6,000-12,000. Bedroom-only with no en-suite is the cheapest spec. Source: 2026 LMB Lofts, Econoloft + 519-town BestBuilders quote data. London/SE add 25%.
Loft Conversion Price Per m² UK 2026
"Per m²" for a loft conversion has two meanings: (a) the build-only cost per m² of usable space, and (b) the total project cost divided by added square metres. Build-only is £1,200-2,500/m². Total project including stairs, bathroom and finishing typically falls £1,400-3,000/m². Here's the breakdown.
| Loft Type | Build-Only £/m² | Total Project £/m² | Per-m² Includes |
|---|---|---|---|
| Velux | £1,000-1,500/m² | £1,200-1,800/m² | Stairs, insulation, plastering, electrics |
| Dormer | £1,200-1,900/m² | £1,400-2,200/m² | Dormer structure + glazing + stairs + insulation |
| Hip-to-Gable | £1,300-2,100/m² | £1,500-2,400/m² | Above + gable wall reconstruction + new hipped roof |
| Mansard | £1,700-2,500/m² | £1,900-2,900/m² | Full roof reconstruction + vertical rear wall + extensive glazing |
| L-Shape | £1,800-2,700/m² | £2,000-3,000/m² | Above + side-return integration + complex roof junctions |
Per m² is measured on usable floor area (head height ≥1.5m). Bathroom fit-out adds £600-1,000/m² to the bathroom area only. London/SE adds 20-30%. Source: 2026 LMB Lofts pricing + Federation of Master Builders Q2 2026 benchmark.
Loft Conversion Cost by House Type: Terrace, Semi, Detached, Bungalow
House type drives both the available loft conversion options and the project cost. A Victorian terrace can typically accommodate a dormer or mansard for £35,000-90,000; a 1960s semi accommodates hip-to-gable + dormer for £45,000-75,000; a bungalow requires a full roof lift starting £40,000.
| House Type | Best Loft Option | Typical Cost 2026 | Typical Add |
|---|---|---|---|
| Victorian / Edwardian terrace (mid) | Rear dormer or L-shape | £40,000-85,000 | +1-2 bedrooms + bathroom |
| Victorian / Edwardian terrace (end) | Hip-to-gable + dormer | £45,000-90,000 | +1-2 bedrooms + bathroom |
| 1930s / 50s semi-detached | Hip-to-gable + dormer | £40,000-75,000 | +1-2 bedrooms + bathroom |
| 1960s-80s detached | Rear dormer or Velux | £30,000-60,000 | +1-2 bedrooms (or 1 + study) |
| Bungalow | Roof lift + dormers | £40,000-95,000 | +2-3 bedrooms + bathroom |
| Cottage (low ceiling) | Velux only (often not viable) | £25,000-45,000 if feasible | +1 small bedroom or study |
| Modern (2000+) standard | Often pre-installed trussed roof — limited options | £35,000-70,000 (truss conversion needed) | +1-2 bedrooms (truss restrictions) |
Trussed roof homes need truss conversion (replacing factory-made trusses with cut roof timbers) — adds £4,000-8,000 vs traditional cut-roof homes. Always check minimum head height (1.5m clear when measured from finished floor) before commissioning surveys.
Loft Conversion vs House Extension: Which Adds More Value in 2026?
When you need more space, the choice between a loft conversion (£30,000-65,000 dormer typical) and a single-storey rear extension (£24,000-60,000) isn't just about money — it's about what you gain. Both add bedrooms or living space; both add value. Here's the 2026 head-to-head.
Loft Conversion Wins When...
- You need bedrooms, not additional living space
- Your garden is small and you don't want to lose any
- Your house is on a small plot in London/major city
- You want maximum value uplift (loft conversions in London + South-East add 20-25% to property value)
- Build time is critical — dormer conversion is 6-10 weeks vs 6-10 weeks for single-storey extension (often quicker due to less groundworks)
Typical ROI 2026: 95-130% (loft conversions deliver highest ROI for terraced/semi-detached properties)
Extension Wins When...
- You want open-plan living — bigger kitchen-diner or family room
- Your loft has limited head height (less than 2.4m at apex)
- You have a trussed-roof home (loft conversion costly)
- You have garden space to spare
- You want a single-storey solution without stairs
Typical ROI 2026: 75-95% single-storey, 90-130% two-storey, 110-150% side return
Loft Conversion Type, Cost Per m² and Planning FAQs
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 loft conversion specialists.