You have looked up at that unused space above your head and thought: there is a bedroom up there, just waiting to happen. Maybe the kids are getting older. Maybe you are working from home and your dining table has become your office. Or maybe you have had another look at what it actually costs to move house in London and decided there has to be a better way.
However, a loft conversion is usually that better way. But the question every UK homeowner asks before anything else is the same: how much is a loft conversion actually going to cost?
For this reason, this guide gives you honest numbers for both UK-wide and London-specific projects, the factors that push costs up, the things that can bring them down, and what to watch out for when you are comparing quotes.
Loft Conversion Cost UK — 2026 National Average
Before we look at London-specific prices, here is the UK-wide picture for 2026.
Overall, the average loft conversion in the UK costs between £40,000 and £75,000 for a standard dormer on a three-bedroom terraced house. A simple Velux conversion can start from around £25,000 in less expensive parts of the country. However, a complex mansard with planning permission can exceed £100,000.
UK Loft Conversion Costs By Region 2026
Where you live in the UK changes the figure significantly:
- North England: £30,000 – £55,000
- Midlands: £35,000 – £60,000
- South East (ex. London): £45,000 – £70,000
- London: £50,000 – £80,000
- South West: £40,000 – £65,000
- Scotland: £32,000 – £58,000
In addition, the UK average across all loft conversion types in 2026 sits at around £52,000. This is significantly higher than five years ago — material costs alone have risen approximately 18% since 2021, driven by steel, timber and insulation price increases.
Therefore, if you are based in London, expect to pay 15 to 25% more than these UK averages. The reasons for this London premium are covered in detail further down this guide.
Loft Conversion Costs in London 2026
London is typically 15 to 25% more expensive than the rest of the UK for loft conversions. Higher labour rates, parking restrictions, tight terraced streets and the logistics of working in a dense city all contribute. Here is what you are realistically looking at in 2026:
Works within your existing roofline with no structural changes to the roof shape. The quickest and most affordable option. Requires good existing headroom of at least 2.3 metres.
The most popular choice for London terraces. Extends vertically from the roof slope to create a proper usable room with full standing height throughout.
Rebuilds a sloping hip roof side as a vertical gable wall. Common on semi-detached homes across Ealing and Hounslow. Often combined with a rear dormer for maximum space.
Restructures the entire roof to near-vertical walls and a flat top. Maximum floor space and the most refined finish. Almost always requires full planning permission.
Loft Conversion Cost Per Square Metre — 2026 UK Rates
A useful way to compare quotes is to look at the cost per square metre of new usable floor space the conversion creates.
| Conversion Type | UK Cost Per M² | London Cost Per M² | Typical Floor Area |
|---|---|---|---|
| Velux / Rooflight | £900 – £1,200 | £1,100 – £1,400 | 15-25 m² |
| Dormer | £1,400 – £1,800 | £1,700 – £2,200 | 25-40 m² |
| Hip-to-Gable | £1,600 – £2,000 | £1,900 – £2,400 | 28-45 m² |
| Mansard | £2,200 – £3,000 | £2,500 – £3,500 | 35-60 m² |
Importantly, these per-m² rates include all standard items: structural work, insulation, plasterboard, plumbing first fix, electrical first fix, staircase, scaffolding and building regulations. However, they do not include bathroom fittings, flooring finishes, decoration or VAT.
For example, if a quote you receive works out at less than £900 per m² for a Velux conversion or less than £1,400 per m² for a dormer, treat it with caution. The price is either incomplete in scope or the builder is using substandard materials and methods that will cause problems later.
Loft Conversion Cost By Property Type
Furthermore, different property types require different approaches and produce different cost ranges. Here is what to budget for the most common UK home types.
Terraced House Loft Conversion Cost
A standard terraced house in London typically gets a rear dormer conversion costing £50,000 to £75,000. Because the narrow plot makes side access challenging, this adds 5-10% to costs through scaffolding and access logistics. Outside London, a terraced house dormer conversion costs £38,000 to £58,000. In addition, a Velux-only conversion on a terrace starts from £25,000 if the existing headroom allows.
Semi-Detached House Loft Conversion Cost
Semi-detached houses suit both dormer and hip-to-gable conversions. For instance, a hip-to-gable plus rear dormer combination is the most popular choice, costing £55,000 to £85,000 in London or £42,000 to £65,000 in the rest of the UK. However, the side gable conversion can also affect your neighbour, so a Party Wall Agreement is usually required. Budget an additional £700 to £1,500 for this.
Detached House Loft Conversion Cost
Detached houses offer maximum flexibility. Typically, a detached dormer with en-suite costs £60,000 to £95,000 in London or £45,000 to £75,000 outside London. Furthermore, mansard conversions on detached homes can exceed £120,000.
Bungalow Loft Conversion Cost
A bungalow conversion is essentially adding a full first floor and therefore costs more than a standard house loft conversion. Expect £75,000 to £130,000 in London or £55,000 to £100,000 elsewhere. In most cases, the roof structure needs significant modification, sometimes a complete rebuild.
Small or Basic Loft Conversion
Alternatively, a budget Velux-only conversion with no bathroom and minimal finishes can be completed for £25,000 to £35,000 in most of the UK. However, this works only if the existing loft has adequate headroom (2.3m minimum) and you do not need to add a bathroom or formal staircase.
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Use Our Free Calculator →What Is Actually Included in Those Prices?
This is where a lot of homeowners get caught out. For example, a quote that looks competitive can quietly expand once work starts if the scope was never clearly agreed from the beginning.
Typically Included
- All structural steelwork and timber joists
- Rooflight or dormer window installation
- Insulation to building regulation standards
- Plasterboarding and skim finish
- New staircase from the floor below
- First fix electrics, sockets and lighting
- Building regulations application and inspections
- Scaffolding
Budget Separately For
- Bathroom or en-suite (add £4,000 to £12,000)
- Flooring — carpet, wood or tile
- Decoration and painting
- Planning permission fees if required
- Architectural drawings (£800 to £2,000)
- Party Wall Agreement if needed
- VAT on all costs above
Therefore, when comparing quotes, make sure you are comparing the same scope. A quote of £48,000 that includes the staircase, electrics and building regulations sign-off is a very different thing from a £48,000 quote that does not mention any of those items.
Why London Loft Conversions Cost More Than You Expect
For example, if you have a friend outside London who had their loft done for £32,000 and you are being quoted £58,000 for the same type of conversion, here is why that gap exists.
Labour Costs Are Higher
A skilled carpenter or structural engineer in West London charges considerably more per day than one in the Midlands. Because the cost of living is higher, wages follow. As a result, this is the single biggest driver of the London premium on any construction project.
Access and Logistics Cost Money
Working on a terraced street in Hayes or Southall means council parking permits, restricted delivery windows and sometimes crane hire to get materials over the roof. In contrast, on a wide detached plot in Surrey, the same job is logistically far simpler and cheaper to run.
Period Properties Require More Care
Victorian and Edwardian homes make up the majority of housing stock across Hillingdon, Ealing and Hounslow. Specifically, these properties have cut timber roof structures that need individual structural assessment before any work can start. Each one is slightly different and therefore requires experienced judgement rather than a standard template.
Building Regulations Are Non-Negotiable
London building control inspectors pay close attention to fire escape routes, structural calculations and insulation standards. Furthermore, unsigned loft conversion work creates serious problems when you come to sell. Cutting corners here is never worth the short-term saving.
Moving house in London costs far more than most people realise. Estate agent fees, stamp duty, legal fees and removal costs on a typical West London upgrade can reach £60,000 to £80,000 in transaction costs alone. In contrast, a loft conversion creates the same extra bedroom for less money, with considerably less stress.
Does a Loft Conversion Add Value in London?
Most people asking about loft conversion cost are really asking: is this actually worth it?
The honest answer is yes, particularly in London. For instance, a 2025 Nationwide report found that adding a large double bedroom and bathroom through a loft conversion can add up to 24% to the value of a three-bedroom home. In West London, where property values are already high, that percentage represents a very significant sum.
| Option | Typical Cost | Disruption | Value Added |
|---|---|---|---|
| Loft Conversion | £50,000 to £80,000 | Stay in your home | Up to 24% on property value |
| Moving House | £60,000 to £80,000 in fees alone | Full upheaval | No uplift on existing property |
| Rear Extension | £40,000 to £70,000 | Stay in your home | 10 to 15% on property value |
Do You Need Planning Permission?
Most loft conversions fall under Permitted Development, meaning no full planning permission is required as long as you stay within certain limits.
Permitted Development Rules
Specifically, the additional roof space must not exceed 40 cubic metres for terraced houses, or 50 cubic metres for detached and semi-detached homes. No extension beyond the front roof slope is permitted. In addition, no balcony or raised platform is allowed. Materials must match the existing house in appearance.
When Full Planning Permission Is Required
However, Permitted Development does not apply if your property is in a conservation area or is listed. For example, parts of Richmond upon Thames, Chiswick and some areas of Ealing have conservation area designations. Furthermore, a mansard conversion almost always requires full planning permission regardless of location.
In all cases, a Lawful Development Certificate from your local council is strongly recommended even where planning permission is not technically required. Specifically, it costs around £200 and creates a formal record that the work was legally carried out, which matters significantly when you come to sell. You can check current guidance at the Planning Portal. We also have a dedicated guide on planning permission for loft conversions in London.
What to Watch Out For When Getting Quotes
Getting three quotes is standard advice and it is good advice. However, there are a few things worth knowing before you start inviting builders in.
Be Wary of Very Low Quotes
A quote that comes in significantly below the others is not a bargain. Usually, it means something is missing from the scope, the builder plans to use cheaper materials, or they intend to return with variation costs once work is underway. In fact, unexpected extras after the job has started are the most common source of disputes between homeowners and builders in loft conversion work.
Ask About Project Management
Some builders quote only for their own trade and leave you to coordinate the electrician, the plasterer and the staircase fitter separately. In contrast, others manage the entire project under one contract with all trades in-house. As a result, the latter approach is less stressful and almost always produces a better finished result.
Check Building Regulations Are Included
Every loft conversion must be signed off under building regulations. This is not optional. Therefore, if a builder suggests you can skip the inspection process, that is a serious warning sign worth walking away from.
Get Everything in Writing
A fixed-price contract that details exactly what is and is not included is the single best protection you have as a homeowner. Importantly, reputable construction companies provide this as standard before any work begins on site.
How Long Does a Loft Conversion Take?
A standard dormer loft conversion typically takes 8 to 12 weeks from the start of construction. However, a more complex mansard or hip-to-gable conversion with full planning permission can take 14 to 20 weeks in total. In contrast, Velux conversions are the quickest, often completing in 4 to 6 weeks.
In almost all cases, you can stay in the house during the work. The main disruption comes during the structural phase in the first two to three weeks, and during installation of the new staircase, which requires a day or two of more significant access to the floor below.
How to Reduce Loft Conversion Costs Without Cutting Corners
A loft conversion is a significant investment. However, there are legitimate ways to reduce costs without compromising quality or building regulations compliance.
01Choose The Right Conversion Type For Your Existing Roof
For example, a Velux conversion on a roof with adequate headroom is dramatically cheaper than a dormer — and can produce a beautiful usable room. In fact, many homeowners spend £20,000 more than needed by defaulting to a dormer when their existing roof structure could support a Velux conversion.
02Avoid Steel Where Timber Will Do
Structural steel adds £2,000 to £5,000 to most loft conversions. However, in some properties, engineered timber joists can carry the load instead at a fraction of the cost. Therefore, always ask your structural engineer whether timber is viable before defaulting to steel.
03Use Velux Windows Instead Of A Full Dormer Where Possible
A pair of Velux windows costs £800 to £1,500. In contrast, a modest dormer adds £8,000 to £15,000. Therefore, if natural light is your main goal rather than headroom, Velux windows alone often achieve the same outcome.
04Plan Plumbing Locations Carefully
Specifically, locating your new en-suite bathroom directly above existing bathroom services (soil pipe, water supply) saves £2,000 to £5,000 in plumbing runs and reduces disruption to the floor below.
05Decorate The Room Yourself
Painting and finishing decoration easily costs £2,000 to £4,000 if your builder does it. However, if you are comfortable with a roller, this is straightforward weekend work and saves real money.
06Get The Project Scope Right In Writing Before Starting
For example, the biggest cost overruns happen mid-project when "extras" are added piecemeal. Therefore, get every detail of the work agreed in a fixed-price contract before the first day of work. As a result, this protects you from variation pricing.
07Time Your Project For Off-Peak Periods
Typically, January to March is the quietest period for loft conversion specialists in London. As a result, some builders offer 5-10% discounts to keep their teams busy during these months.
Frequently Asked Questions
How much does a loft conversion cost in London in 2026?
A dormer loft conversion in London costs between £50,000 and £80,000. A Velux conversion starts from around £25,000. Meanwhile, a mansard conversion can reach £120,000 or more. Overall, London prices are typically 15 to 25% higher than the rest of the UK due to higher labour costs and more complex site logistics.
How much does a loft conversion cost per square metre in 2026?
A typical UK loft conversion costs £1,400 to £1,800 per square metre for a dormer, or £900 to £1,200 for a Velux. However, London rates are 20-25% higher. Importantly, these figures cover the structural conversion only and exclude bathroom fittings, flooring finishes, decoration and VAT.
What is the cheapest type of loft conversion?
A Velux or rooflight conversion is the most affordable option, starting from £25,000 in most of the UK or £30,000+ in London. Specifically, it requires existing headroom of at least 2.3 metres and works within the existing roofline with no structural changes to the roof shape.
How much does a loft conversion cost in a terraced house?
A standard rear dormer conversion on a terraced house costs £50,000 to £75,000 in London or £38,000 to £58,000 elsewhere in the UK. In addition, Velux-only conversions on terraced houses start from around £25,000 if headroom allows.
How much does a loft conversion cost in a semi-detached house?
Typically, a combined hip-to-gable plus rear dormer conversion (the most common choice for semi-detached) costs £55,000 to £85,000 in London. In contrast, a simple dormer-only conversion on a semi costs £48,000 to £72,000 in London.
Do I need planning permission for a loft conversion in London?
Most loft conversions fall under Permitted Development and do not require full planning permission. However, if your property is in a conservation area, or if you are planning a mansard conversion, planning permission will be required. In all cases, a Lawful Development Certificate is recommended regardless.
How much value does a loft conversion add to a London home?
According to a 2025 Nationwide report, a loft conversion adding a large double bedroom and bathroom can add up to 24% to the value of a three-bedroom home. In London, where property values are high, this represents a particularly strong return on investment.
Is a loft conversion cheaper than moving house?
Yes, significantly so in London. For example, moving house in London costs £60,000 to £80,000 in transaction costs alone (stamp duty, estate agent fees, legal fees, removal costs). In contrast, a typical loft conversion creates the same extra bedroom for £50,000 to £80,000, with no transaction costs and no upheaval.
Do I need an architect for a loft conversion?
Not always. For example, for straightforward Permitted Development conversions, your chosen loft conversion specialist can produce all required drawings in-house. However, for mansard conversions, conservation area properties, or projects requiring planning permission, an architect is usually recommended. Architectural drawings cost £800 to £2,000.
Can I stay in my house during a loft conversion?
Yes. In almost all cases you can remain in the property throughout the work. Typically, the main disruption periods are during initial structural work and staircase installation. However, a well-managed project minimises impact on your daily routine as much as possible.
How long does a loft conversion last before needing repairs?
Typically, a properly built loft conversion should require no major repairs for 30+ years. Furthermore, the roof itself, including the new dormer or mansard, will last 40-60 years before needing reroofing. In addition, annual gutter clearing and five-yearly external inspections are the only routine maintenance required.
When is the best time to start a loft conversion in London?
Typically, January to March is the quietest period for London loft conversion specialists. As a result, booking during these months can sometimes secure a 5-10% discount. In contrast, spring through summer is the most popular period and typically requires booking 3-4 months in advance.
Thinking About a Loft Conversion in West London or Surrey?
Signature Build Properties carry out loft conversions across Hayes, Hillingdon, Ealing, Hounslow, Richmond upon Thames and Surrey. Specifically, we manage every aspect of the project in-house, covering structural work, carpentry, electrics, plastering and building regulations, under one fixed-price contract with no hidden costs.
If you would like an honest assessment of what your loft conversion would involve and what it would cost, we offer free no-obligation site visits. In addition, we will come to you, look at the space properly and give you a written quote that tells you exactly what you are getting.
You can also visit our loft conversion service page to learn more about the types of conversion we carry out across West London and Surrey.
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