Loft Conversion Cost by Type: 2026 UK Price Guide
The type of loft conversion you choose is the single biggest driver of your budget. In 2026, a Velux (rooflight) conversion is the cheapest at £15,000–£30,000, a rear dormer runs £30,000–£81,000, a hip-to-gable £33,000–£93,000 and a mansard — the priciest — £38,000–£113,000 nationally. This guide compares every UK loft conversion type side by side: what each one actually is, which houses it suits, what it costs and where it stands on planning permission.
- All five main loft types compared on cost, space and planning
- Dormer vs hip-to-gable head-to-head for semis
- Costs by house type — terrace, semi, detached, bungalow
- Free quotes from vetted local loft specialists
Loft Conversion Cost by Type: Quick Answer
Ranked cheapest to priciest in 2026: a Velux / rooflight conversion is the cheapest at £15,000–£30,000 (most complete projects £25,000–£40,000), a rear dormer — the UK’s most popular type — runs £30,000–£81,000, a hip-to-gable costs £33,000–£93,000, an L-shaped dormer £55,000–£100,000, and a mansard is the priciest at £38,000–£113,000, with London mansards occupying the top of that range.
The gap between types comes down to how much of the roof is rebuilt: a Velux leaves the roof untouched, a dormer replaces part of the rear slope, a hip-to-gable rebuilds the end of the roof, and a mansard reconstructs the whole rear slope. Full background figures are in our loft conversion cost guide, or get a personalised range in 30 seconds with the loft conversion cost calculator.
Jump to: Comparison table · Velux · Dormer · Hip-to-gable · Mansard · Modular · Dormer vs hip-to-gable · By house type · FAQs
Loft Conversion Types Compared: Cost, Space & Planning (2026)
These are the national 2026 cost ranges from our live 519-town dataset, spanning basic bedroom-only specifications up to premium builds with an en-suite. London and the South East sit towards the upper end of each range — typically 35–45% above the national average at the top of the market.
| Conversion type | National cost 2026 | Space gained | Planning position | Best for |
|---|---|---|---|---|
| Velux / rooflight | £15,000 – £30,000 | 15–25m² | Usually Permitted Development | Tall, steeply pitched roofs; budget builds |
| Rear dormer | £30,000 – £81,000 | 25–40m² | Usually Permitted Development | Most UK terraces and semis |
| L-shaped dormer | £55,000 – £100,000 | 40–70m² | Often planning + party wall | Victorian terraces with a rear addition |
| Hip-to-gable | £33,000 – £93,000 | 30–50m² | Usually Permitted Development | Hipped-roof semis, end-of-terrace, detached |
| Mansard | £38,000 – £113,000 | 35–60m² | Usually needs full planning | London terraces; maximum floor area |
| Bungalow roof lift | £40,000 – £95,000 | 40–75m² | Planning typically required | Bungalows with an adequate roof span |
PD = Permitted Development (no planning application needed, within limits). Ranges include structural work, staircase, insulation, plastering and decoration; premium upper ends include an en-suite. A bathroom add-on alone typically costs £6,000–£12,000.
Velux / Rooflight Loft Conversion — £15,000 to £30,000
What it is: the simplest conversion of all. Your roof shape stays exactly as it is — the builder insulates the loft, boards and strengthens the floor, fits a proper staircase, and sets Velux-style windows into the existing roof slope for daylight. No dormer, no structural reshaping, no change to your home’s outline. Because nothing is rebuilt, it is both the cheapest and the fastest type: the simplest jobs take just 1–2 weeks on site, and even allowing for lead-in most are done inside 4–6 weeks.
What it costs in 2026: a rooflight-only bedroom conversion runs £15,000–£30,000 nationally. Most complete Velux projects land between £25,000 and £40,000 once everything is included: the staircase typically costs £2,000–£4,000, insulation, plastering and electrics £8,000–£15,000, and decoration £1,500–£3,000. On a per-square-metre basis that works out at £1,000–£1,500/m² for the build, the lowest of any type.
When it suits: the catch is head height. Because the roof is not altered, everything depends on what is already there — as a rule of thumb you want at least 2.2m from the top of the ceiling joists to the underside of the ridge board, and 2.4m or more converts comfortably. Steep Victorian and Edwardian roofs are ideal; shallow modern pitches frequently fall below the line. Expect 15–25m² of usable space with sloping ceilings — fine for a bedroom or study, less suited to a full master suite.
Planning position: rooflight conversions are the least contentious of all — they usually fall under Permitted Development because the roof plane is barely altered. The main caveats are conservation areas, listed buildings and flats, where consent is generally still needed, and rooflights facing the highway can attract conditions in sensitive areas. Check your specific situation on the Planning Portal, and see our guide to loft conversion planning permission in 2026.
Dormer Loft Conversion Cost — £30,000 to £81,000
What it is: the UK’s most popular conversion, and the default choice for most terraces and semis. A box-shaped structure is built out from the rear roof slope, with a flat roof and a vertical rear wall, turning cramped sloping space into a full-height room with a normal window. Most rear dormers include an en-suite shower room and Velux windows on the front slope, keeping the street-facing roofline unchanged.
What it costs in 2026: the typical UK band is £30,000–£65,000, within a full national spread of £30,000–£81,000 that reaches its upper end with premium specifications in London (the London range alone is £47,000–£81,000). Within the typical band: a standard rear dormer is £30,000–£50,000, a side dormer £35,000–£55,000 and a full-width rear dormer £40,000–£65,000. You gain 25–40m² of full-height space over a 6–10 week build. Here is a realistic mid-range budget for a rear dormer with en-suite:
| Cost element | 2026 range |
|---|---|
| Structural & roofing works | £20,000 – £28,000 |
| Staircase design & installation | £3,500 – £6,000 |
| En-suite bathroom | £4,000 – £8,000 |
| Electrics, plumbing & insulation | £3,000 – £5,000 |
| Professional fees & building control | £2,000 – £4,500 |
| Contingency (10–15%) | £3,500 – £6,000 |
| Likely total | £36,000 – £57,500 |
Mid-range finish, national pricing; London and the South East add 35–45%.
L-shaped dormer — £55,000 to £100,000
On Victorian and Edwardian terraces with a rear addition (the “side return” wing housing the kitchen or bathroom), a second dormer can be built over that back addition and joined to the main rear dormer — forming an L shape when seen from above. It is the biggest dormer format, adding 40–70m² — enough for two bedrooms and a bathroom — at £55,000–£100,000 over a 12–16 week build. Because of the volume involved and the party walls on both sides, L-shaped dormers commonly involve a planning application and party wall agreements, so allow for a longer programme.
When it suits: almost any house with a usable rear roof slope and around 2.2m of existing ridge height — mid-terraces, gable-ended semis and detached homes alike. It is the go-to answer when a Velux conversion would leave too little head height, which is most UK homes.
Planning position: rear dormers on houses usually fall under Permitted Development, within volume limits of 40m³ on terraces and 50m³ on semi-detached and detached homes, provided the dormer does not rise above the existing ridge, extend forward of the principal elevation or include a balcony. Front-facing dormers need a full application, as do dormers on flats, listed buildings and homes in conservation areas — larger jobs are covered in our guide to planning permission for a two-storey rear dormer. Even where PD applies, get a Lawful Development Certificate — buyers’ solicitors increasingly ask for one.
Hip-to-Gable Loft Conversion Cost — £33,000 to £93,000
What it is: many semi-detached, end-of-terrace and detached homes — especially 1930s to 1950s builds — have a hipped roof, which slopes down over the end of the house as well as front and back. That sloping hip steals most of the usable loft space. A hip-to-gable conversion removes the hip and builds the end wall straight up into a vertical gable, extending the ridge across the full length of the house — and in practice it is almost always paired with a rear dormer to maximise the gain.
What it costs in 2026: a typical hip-to-gable project runs £33,000–£70,000, within a full national spread of £33,000–£93,000 (London £51,500–£93,000; the North and Wales from around £33,000–£60,000). You gain 30–50m² over an 8–12 week build. A realistic worked budget for a hip-to-gable plus dormer creating two bedrooms — including the staircase (£3,500–£6,000), a bathroom (£5,000–£10,000), finishes, fees, party wall costs and contingency — comes to £49,000–£80,000 at a mid-range finish.
When it suits: it is only relevant if you have a hipped roof — if your end wall already goes straight up to a point (a gable), you do not need one, and a straightforward rear dormer will serve you better. For hipped-roof semis and end-of-terrace homes it is usually the best-value route to a proper master suite or two extra rooms; detached homes with hips on both ends can even convert to a double hip-to-gable.
Planning position: hip-to-gable conversions on semi-detached and end-of-terrace houses usually fall under Permitted Development within the same 50m³ volume allowance, because the new roof does not rise above the existing ridge. The caveats: the volume of a hip-to-gable plus dormer together counts against the allowance, matching materials are required, and conservation areas or Article 4 directions remove PD rights altogether — in which case a full application (typically an 8–10 week determination) is needed. Verify your street on the Planning Portal before committing to drawings.
Mansard Loft Conversion Cost — £38,000 to £113,000
What it is: the most spacious — and most expensive — conversion. The entire rear roof slope is removed and rebuilt as a near-vertical wall, typically pitched at 70–72 degrees, with a shallow, almost flat roof on top. Where a dormer pokes a box out of the roof, a mansard effectively replaces the roof with an extra storey that reads as part of the original architecture — the classic London terrace solution.
What it costs in 2026: a typical UK mansard runs £38,000–£90,000, and the full national spread reaches £113,000 — the London range is £59,000–£113,000, and mansards consistently command around 25–35% more than an equivalent dormer because of the sheer amount of roof reconstruction involved. At £1,700–£2,500/m² build-only it is the priciest type per square metre, but it also delivers the most: 35–60m² of near-full-height space across the whole rear of the house, over a 10–14 week build.
When it suits: city terraces where every square metre counts, homes where a dormer would not create enough head height, and streets where the planners prefer the traditional mansard profile to a boxy dormer. If you need two proper bedrooms and a bathroom out of a terrace loft, the mansard (or an L-shaped dormer) is usually the way to get there.
Planning position: unlike dormers, mansards almost always need full planning permission, because rebuilding the roof to a new profile goes beyond Permitted Development. Allow 8–10 weeks for a determination on top of the build. In conservation areas the picture cuts both ways: a well-detailed mansard is sometimes the only loft style a council will entertain on a period terrace, yet applications there are also the most frequently refused — local precedent matters enormously, so an architect or specialist who knows your borough is worth their fee. Start with the Planning Portal and our 2026 loft planning guide.
Modular (Prefabricated) Loft Conversion
What it is: instead of building the new roof structure piece by piece on site, the conversion — walls, floor, windows, sometimes even first-fix wiring and plumbing — is manufactured off-site as one or more modules, the existing roof is removed, and the modules are craned into place in a day or two before being weatherproofed and finished internally. It is the same end product as a conventional dormer, roof lift or mansard, assembled a different way.
Why choose it: speed and certainty. The house is open to the weather for days rather than weeks, disruption drops sharply, and factory build quality is consistent. It comes into its own on bungalow roof lifts — where the whole roof is replaced and raised — a project type that runs £40,000–£95,000 in 2026 and adds 40–75m². The trade-offs: you need crane access (a real constraint on tight terraced streets), and the design must be finalised early, because late changes are expensive once fabrication starts.
What it costs: modular specialists price each job against the equivalent conventional conversion — the dormer, roof-lift or mansard bands above are the right benchmarks — with spend shifting from on-site labour to fabrication and crane hire. Because access and module count vary so much house to house, get itemised quotes rather than relying on a generic range: our loft conversion quote service can match you with specialists offering both build methods.
Planning position: exactly the same rules as the conventional equivalent — the council cares about the finished form, not the construction method. A modular rear dormer within volume limits can still be Permitted Development; a modular roof lift or mansard that changes the roof profile needs a full application, and conservation-area constraints apply as usual.
Installed Cost by Conversion Type: 2026 at a Glance
Bars show the midpoint of each type’s national 2026 range, with the full range beneath each bar. The rear dormer — highlighted — remains the UK’s most popular choice because it delivers full head height at a mid-table price and usually stays within Permitted Development.
Midpoints of the national ranges shown in the comparison table above: Velux £15k–£30k, dormer £30k–£81k, hip-to-gable £33k–£93k, mansard £38k–£113k, L-shaped dormer £55k–£100k. Ranges span basic to premium specification including en-suite; London and the South East sit towards each upper end.
Dormer vs Hip-to-Gable: Head-to-Head for Semis and End-of-Terrace
This is the most common decision UK homeowners face, because it is settled by your roof shape. Stand outside and look at the end of your house: if the roof slopes down over the end wall, you have a hip and the hip-to-gable route is on the table; if the end wall rises to a point, you already have a gable and a rear dormer is the natural choice.
| Rear dormer | Hip-to-gable (+ dormer) | |
|---|---|---|
| Typical UK cost 2026 | £30,000 – £65,000 | £33,000 – £70,000 |
| Full national spread | £30,000 – £81,000 | £33,000 – £93,000 |
| London range | £47,000 – £81,000 | £51,500 – £93,000 |
| Floor area added | 25–40m² | 30–50m² |
| Build time on site | 6–10 weeks | 8–12 weeks |
| Roof shape needed | Any roof with a usable rear slope | Hipped roof (slopes on the end as well) |
| Planning position | Usually Permitted Development | Usually Permitted Development |
| Best for | Mid-terrace and gable-ended semis | Hipped semis, end-of-terrace and detached |
The verdict: with a hipped roof, hip-to-gable plus dormer is usually worth the extra £3,000–£5,000 at the typical band — it turns an awkward triangular loft into a full-width storey with up to 10m² more than a dormer alone. With a gable end already, a rear dormer gets you full-height space without rebuilding the end of the roof. Both routes usually stay within Permitted Development, so planning rarely tips the decision.
Loft Conversion Cost by House Type (2026)
Your house largely picks your conversion type for you — and with it, your budget. Steep-roofed Victorian terraces convert most easily; hipped 1930s semis point to hip-to-gable; post-1960s homes with factory-made trussed roofs need the trusses replaced with cut timbers first, adding £4,000–£8,000 before anything else starts.
| House type | Best loft option | Typical cost 2026 | What you gain |
|---|---|---|---|
| Victorian / Edwardian mid-terrace | Rear dormer or L-shaped dormer | £40,000 – £85,000 | +1–2 bedrooms + bathroom |
| Victorian / Edwardian end-of-terrace | 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 ceilings) | Velux only — often not viable | £25,000 – £45,000 if feasible | +1 small bedroom or study |
| Modern (2000+) trussed roof | Truss conversion + dormer | £35,000 – £70,000 | +1–2 bedrooms (truss work needed) |
Always check head height first: you want roughly 2.2m from the top of the ceiling joists to the underside of the ridge before commissioning surveys, and usable floor area is measured where head height is at least 1.5m. Comparing quotes on different-sized lofts? Build-only rates run £1,000–£2,500/m² depending on type — the per-m² FAQ below has the full type-by-type breakdown.
What Moves the Price Within Each Type
Two dormers on the same street can be £20,000 apart. These six factors explain most of the difference:
1. How much roof gets rebuilt. This is the type decision itself — a Velux touches nothing, a mansard rebuilds the entire rear slope — and it is why the type sets the baseline before any other choice you make.
2. Available head height. Below roughly 2.2m at the ridge, the floor has to be lowered into the rooms beneath, adding £2,000–£6,000 and real structural complexity. Some shallow modern roofs are better served by switching type — a dormer or roof lift creates height a Velux cannot.
3. The staircase. Building Regulations require a fixed staircase, not a ladder. A standard straight flight costs £2,500–£5,000 installed; bespoke or space-saving designs run £4,000–£8,000 and eat into the room below.
4. The bathroom. An en-suite typically accounts for 25–30% of the whole budget: a compact shower room is £4,000–£7,000, a premium en-suite £8,000–£15,000, and a complex soil pipe run can add £1,500–£3,000. Bedroom-only is always the cheapest specification.
5. Roof structure and party walls. Pre-1960s cut roofs convert most easily; modern trussed roofs need £4,000–£8,000 of truss conversion and steelwork. On terraces and semis, the Party Wall Act adds £800–£2,500 and up to two months of notice if neighbours appoint surveyors.
6. Where you live. London loft specialists command a bigger premium than almost any other trade — 35–45% above the national average at the top of the market. More on regions below.
How to Keep Your Loft Conversion on Budget
- Let your roof pick the type — do not over-build. If you have 2.4m+ at the ridge, a £25,000–£40,000 Velux project may deliver everything you need; jumping to a dormer you do not strictly need is the single most expensive upgrade on the menu.
- Choose a straight staircase. A straight or quarter-landing flight is £1,500–£2,500 cheaper than a bespoke space-saving design — decide early, because the staircase position drives the whole layout.
- Question the en-suite. A bathroom add-on runs £6,000–£12,000. If the family bathroom is one floor down, a bedroom-only spec now (with plumbing first-fixed for later) keeps the initial budget lean.
- Serve party wall notices early. Prompt written consent from neighbours costs nothing; disputes mean surveyors at £800–£2,500 and months of delay.
- Use a loft specialist, not a general builder. Firms converting dozens of lofts a year price sharper, know the PD limits cold and make fewer expensive mistakes.
- Hold a 10–15% contingency. Lofts uncover surprises — especially in older houses. A contingency you do not spend is a happy ending, not wasted planning.
- Compare at least three quotes. Our free loft conversion quote service matches you with up to three vetted local specialists in 24 hours — the fastest way to find the fair local price for your type.
Regional Pricing: the Same Type, Very Different Bills
Region shifts every band on this page. A rear dormer that costs £30,000–£52,000 in South Wales or the North East runs £47,000–£81,000 in London; a mansard rises from £38,000–£73,000 in the cheapest regions to £59,000–£113,000 in the capital. London and the South East consistently price 35–45% above the national average at the top of the market — a bigger premium than most other trades, driven by specialist demand, scaffold licences, tight urban access and conservation-area constraints. The full region-by-region table for dormer, hip-to-gable and mansard conversions is on our loft conversions overview, and the main cost guide links to town-level pricing across all 519 towns we cover.
Loft Conversion Cost by Type: FAQs
A Velux (rooflight) conversion is the cheapest loft conversion type in 2026. A rooflight-only bedroom conversion runs £15,000–£30,000 nationally, and most complete Velux projects with the staircase, insulation and decoration included fall between £25,000 and £40,000. It is the cheapest because the roof shape is left completely untouched — the trade-off is sloping ceilings and the need for at least 2.2m of existing head height at the ridge.
A dormer loft conversion typically costs £30,000–£65,000 in the UK in 2026, with the full national spread running to £81,000 for premium specifications in London and the South East. As a guide: a rear dormer is £30,000–£50,000, a side dormer £35,000–£55,000 and a full-width rear dormer £40,000–£65,000. Expect 25–40m² of added floor area and 6–10 weeks on site.
A hip-to-gable loft conversion costs £33,000–£70,000 for a typical UK project in 2026, rising to £93,000 at the top of the national range for premium London jobs (London alone runs £51,500–£93,000). It is almost always paired with a rear dormer, adds 30–50m², and takes 8–12 weeks. It suits semi-detached, end-of-terrace and detached homes with a hipped roof.
A mansard loft conversion costs £38,000–£90,000 for a typical UK project in 2026; in London, where mansards are most common, budgets run £59,000–£113,000. It is the most expensive type because the rear roof slope is rebuilt as a near-vertical wall at roughly 70–72 degrees, delivering the largest space gain of any conversion (35–60m²) over a 10–14 week build. Mansards almost always need full planning permission.
A Velux (rooflight) loft conversion costs £15,000–£30,000 for a rooflight-only bedroom, and most complete projects land at £25,000–£40,000 once the staircase (£2,000–£4,000), insulation, plastering and electrics (£8,000–£15,000) and decoration (£1,500–£3,000) are included. You need around 2.2–2.4m of head height at the ridge for it to be viable; the simplest jobs take just 1–2 weeks on site.
An L-shaped dormer — a rear dormer plus a second dormer over the back addition (side return) — costs £55,000–£100,000 in 2026. It is the biggest dormer format, adding 40–70m², enough for two bedrooms and a bathroom, over a 12–16 week build. It suits Victorian and Edwardian terraces with a rear addition, and usually involves planning permission and party wall agreements.
For a 1930s–1950s semi with a hipped roof, a hip-to-gable plus rear dormer is usually the best-value option at £40,000–£75,000, because it converts the sloping hip end into a vertical gable and maximises floor area. If your semi already has a gable end, a straightforward rear dormer (£30,000–£65,000 typical) does the job. A specialist will confirm which applies during a free site survey.
Most rear dormer, Velux and hip-to-gable conversions on houses fall under Permitted Development in England, within volume limits of 40m³ for terraces and 50m³ for semi-detached and detached homes, provided they do not extend forward of the principal elevation, rise above the ridge or add a balcony. Mansard conversions almost always need full planning permission, as do conversions on flats, listed buildings and homes in conservation areas. Even when PD applies, get a Lawful Development Certificate.
Measure from the top of the ceiling joists to the underside of the ridge board. Specialists want at least 2.2m before committing to any conversion, and 2.4m or more converts comfortably. A Velux conversion depends entirely on existing height because the roof is not altered; a dormer or mansard creates full head height by rebuilding part of the roof. Below 2.2m, floor lowering adds £2,000–£6,000, and Building Regulations require 2m over stairs and walking areas in the finished room.
Build-only costs in 2026 run £1,000–£1,500/m² for a Velux, £1,200–£1,900/m² for a dormer, £1,300–£2,100/m² for a hip-to-gable, £1,700–£2,500/m² for a mansard and £1,800–£2,700/m² for an L-shaped dormer. Total project figures including stairs, bathroom and finishing typically fall between £1,200 and £3,000/m² depending on type, measured on usable floor area with at least 1.5m head height.
A well-executed loft conversion with an en-suite typically adds 15–25% to property value whichever type you choose — the extra bedroom is what moves the valuation. Bigger conversions (mansard, L-shaped, hip-to-gable plus dormer) add more absolute space, and in London and the South East the return is strongest because moving costs are high. Whatever the type, insist on a Building Regulations completion certificate: it is essential for mortgages, insurance and resale.
Get Accurate Prices for Your Conversion Type
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