Loft Conversion Cost UK: How Much Does a Loft Conversion Cost in 2026?
A loft conversion is still one of the highest-return home improvements in the UK, but the price varies widely by type, size, property and location. This 2026 guide breaks down realistic costs by conversion type, per square metre, by property and by region, plus professional fees and what a premium design-and-build loft conversion in London actually costs. All figures are updated for 2026 and drawn from live UK projects.
How much does a loft conversion cost?
A loft conversion in the UK typically costs £20,000 to £75,000 in 2026, or about £2,400 to £4,100 per square metre (build only). A simple rooflight conversion starts around £20,000 to £40,000, a dormer runs £40,000 to £70,000, and a mansard, the most expensive type, costs £55,000 to £95,000. London projects cost roughly 20 to 40 percent more, and professional fees add a further £6,000 to £15,000.
| Loft conversion type | Typical UK cost (2026) | London (approx.) |
|---|---|---|
| Rooflight / Velux | £20,000 - £40,000 | £28,000 - £50,000 |
| Dormer (standard rear) | £40,000 - £70,000 | £50,000 - £90,000 |
| L-shaped dormer | £55,000 - £90,000 | £70,000 - £120,000 |
| Hip-to-gable (with dormer) | £50,000 - £85,000 | £65,000 - £110,000 |
| Mansard | £55,000 - £95,000 | £75,000 - £140,000 |
Loft conversion cost by type (2026)
Rooflight (Velux) loft conversion cost: £20,000 to £40,000
The cheapest option. Rooflight windows are set into the existing roofline, with floor strengthening, insulation, plasterboarding and a new staircase. There is no change to the roof shape, it is usually permitted development, and it is the fastest type to build. It works best where you already have enough head height, around 2.2 metres at the ridge.
Dormer loft conversion cost: £40,000 to £70,000
The most popular UK choice. A box-shaped structure replaces one roof slope to create full headroom and full-height windows. The cost rises with size, a full-width dormer, or an added bathroom. An L-shaped dormer, which adds a second dormer over a rear addition, typically costs £55,000 to £90,000 and creates the most usable space on a terraced house.
Hip-to-gable loft conversion cost: £50,000 to £85,000
For end-of-terrace, semi-detached and detached homes. The sloping hip end of the roof is rebuilt as a vertical gable wall, almost always combined with a rear dormer to maximise space. It involves more structural work than a dormer, which is why it costs more.
Mansard loft conversion cost: £55,000 to £95,000
The most expensive and most space-creating type. The rear roof slope is rebuilt at roughly 72 degrees to form a near-vertical wall and a flat roof. A mansard always needs planning permission and a structural engineer, and is common on period London terraces.
Loft conversion cost per square metre
Excluding finishes such as windows, flooring and sanitaryware, a UK loft conversion costs £2,400 to £4,100 per square metre. The variation comes from the conversion type, the scale of the roof alterations, access, finish level and location. Use the per-square-metre figure as a sanity check: a typical 25 to 30 square metre dormer at around £2,500 per square metre lands at roughly £62,000 to £75,000 before premium finishes.
Loft conversion cost by property type
- Terraced house: a dormer or L-shaped dormer is most common, at £45,000 to £90,000.
- Semi-detached: a hip-to-gable plus dormer is typical, at £50,000 to £90,000.
- Detached: most options are open and footprints are larger, at £45,000 to £110,000.
- Bungalow: often needs structural reinforcement and a new staircase footprint, at £45,000 to £80,000.
- Flat or maisonette: depends on the lease, freeholder consent and party wall, from £40,000 plus legal and licence costs.
Is an attic conversion the same as a loft conversion?
Yes. An attic conversion and a loft conversion are the same thing in the UK and cost the same, £20,000 to £75,000 depending on type. "Attic" is used more in Scotland, Ireland and the US, and "loft" in England and Wales. The costs, planning rules and build times are identical. What changes the price is the conversion type and your location, not the word used.
Loft conversion cost in London and by region
Building costs are highest where property prices, labour rates and access constraints are highest. London adds roughly 20 to 40 percent over the UK average, driven by parking and skip restrictions, the congestion and ULEZ zones, higher labour and delivery costs, and tighter planning. Scotland and the South East are next, while Northern Ireland and the North of England are the cheapest. A dormer that costs £55,000 in the Midlands can be £80,000 or more in inner London.
Professional fees (2026)
On top of the build, budget £6,000 to £15,000 for the following.
- Certificate of Lawful Development (when permitted development applies): around £130 in England. A householder planning application (when permission is needed) is around £258. Check current fees on the Planning Portal.
- Architectural and design drawings: £3,000 to £6,000.
- Structural engineer's calculations: £1,800 to £3,600.
- Party wall agreement: £1,000 to £2,000 per neighbour if a surveyor is appointed, and often free if your neighbour consents in writing. See our guide to the party wall agreement for a loft conversion.
- Building Control certificate: around £1,000.
A design-and-build company usually rolls design, structural and sometimes planning fees into a single quote.
What makes a loft conversion cost more?
Costs rise above average when there are multiple party-wall neighbours or a dispute, complex structural design needing extra steels or columns, difficult site access, an older building with surprises on strip-out, height (flats need more scaffolding and hoisting), bespoke or high-end finishes, or a compressed timeline that needs more trades on site at once.
Budget vs premium: what you get at each price
| Tier | Typical specification | Indicative cost (standard dormer) |
|---|---|---|
| Budget | Smaller contractor, standard finishes, minimal structural work | £40,000 - £55,000 |
| Mid-range | Established builder, better insulation and glazing, en-suite | £55,000 - £75,000 |
| Premium (design and build) | Architect-led, in-house engineers, bespoke joinery, prime finishes, full project management | £80,000+ |
Premium and prime-London pricing: what houseUP delivers
houseUP is a high-end design-and-build contractor working across prime London boroughs including Chelsea, Kensington, Hampstead and Chiswick. Our loft conversions are architect-led, structurally engineered in-house and finished to a bespoke specification, with full project management and a fixed, transparent quote. At that level, a high-specification dormer in prime London typically runs £90,000 to £160,000, and a bespoke mansard £130,000 to £210,000 or more, depending on size, planning constraints and finish. Get a free, fixed quote.
Is a loft conversion worth it? Value added to your home
A loft conversion typically adds 15 to 25 percent to a property's value, usually the strongest return of any extension when it adds a double bedroom with an en-suite, because it moves the home into a higher bedroom bracket on Rightmove and Zoopla. On a £600,000 home, a £70,000 dormer that adds a bedroom with en-suite can add £90,000 to £150,000 of value. See our comparison of loft versus basement conversion value.
How long does a loft conversion take?
On site, a rooflight takes 4 to 6 weeks, a dormer 6 to 8 weeks, and a mansard 10 to 12 weeks or more. Add 4 to 8 weeks beforehand for design, structural calculations, building-regulations sign-off and, if needed, planning.
Real houseUP loft conversions
- Luxury loft with roof terrace, Hammersmith: a premium mansard with roof-terrace access and bespoke finishes in West London, in the £130,000 to £210,000 range typical of our prime-London projects.
- Loft and side extension with full renovation, Willesden: a dormer loft combined with a side-return extension and a whole-house refurbishment in North West London.
How to budget for your loft conversion
Start from the value uplift by asking two local estate agents, choose the type that suits your roof and budget, then get a fixed design-and-build quote so the design, structural and management fees are clear up front. See our design-and-build loft conversions in London or get a free quote from houseUP.
Frequently asked questions
How much does a loft conversion cost in the UK in 2026?
Between £20,000 and £75,000 for most types, or about £2,400 to £4,100 per square metre. A rooflight costs £20,000 to £40,000, a dormer £40,000 to £70,000, and a mansard £55,000 to £95,000. London adds roughly 20 to 40 percent.
How much does a dormer loft conversion cost?
A standard rear dormer costs £40,000 to £70,000 in the UK in 2026, or £50,000 to £90,000 in London. An L-shaped dormer runs £55,000 to £90,000. Adding an en-suite typically adds £8,000 to £15,000.
What is the cheapest type of loft conversion?
A rooflight or Velux conversion is the cheapest at £20,000 to £40,000, because it keeps the existing roofline and needs no major structural change. You do need enough existing head height, about 2.2 metres at the ridge.
Do I need planning permission for a loft conversion?
Most loft conversions are permitted development and do not need planning permission, provided you stay under 40 cubic metres for a terraced house or 50 cubic metres for a semi or detached home, and match the existing materials. Mansards, conservation areas and Article 4 zones usually do need permission. You always need Building Regulations approval.
Does a loft conversion add value to your home?
Yes, typically 15 to 25 percent, the best return of any extension when it adds a double bedroom with an en-suite, because it raises the property's bedroom count.
How long does a loft conversion take?
Between 6 and 12 weeks on site for most types: a rooflight 4 to 6 weeks, a dormer 6 to 8 weeks, and a mansard 10 to 12 weeks or more, plus 4 to 8 weeks beforehand for design, structural sign-off and any planning.
Vinz is the CEO and co-founder of houseUP. He is a true authority in financial planning and risk management, coming from years of working in financial services and digital payment industries
houseUP is a construction company in London, specialised in high end residential and commercial projects.
