Loft Conversion Cost per m²: What You'll Actually Pay

If you are budgeting for a loft conversion, the cost per square metre is the single most useful figure to anchor your planning. In 2026, UK homeowners pay between £1,500 and £2,500 per m² for a standard loft conversion, according to data from Checkatrade and the Federation of Master Builders (FMB). But that range hides significant variation — by conversion type, location, finish, and hidden costs that rarely appear in headline quotes.

This guide breaks down exactly what is included in that per-m² figure, what pushes it higher or lower, and how to get a reliable estimate before you speak to a builder.

Table of Contents

1. The Headline Figure: Cost per m² in 2026
2. Cost per m² by Conversion Type
3. What Is Included in the Per-m² Price?
4. What Is NOT Included?
5. Regional Price Variations per m²
6. Factors That Increase Cost per m²
7. How to Reduce Your Cost per m²
8. Comparing Loft Conversion vs. Extension per m²
9. Getting an Accurate Quote
10. Frequently Asked Questions

The Headline Figure: Cost per m² in 2026

The UK average for loft conversion construction in 2026 sits at roughly £2,000 per m². Here is how that breaks across the quality spectrum:

These figures represent construction costs only — design fees, planning, and professional services sit on top. For a realistic total budget, add 15–20% to cover those extras.

Sources: Checkatrade Cost Guides 2026; FMB Pricing Survey; HomeOwners Alliance.

Cost per m² by Conversion Type

The type of loft conversion you choose is the biggest driver of per-m² cost. Here is how each option compares.

Velux (Rooflight) Conversion

• Cost per m²: £1,500 – £2,000
• Why the range: The lower end applies to straightforward installations with minimal electrics and standard windows. The upper end covers larger rooflight arrays, upgraded insulation, and better finishes.

Velux conversions are cheapest because they do not alter the roof structure. You are essentially finishing the existing space. The trade-off is limited headroom and floor area compared to a dormer or mansard.

Dormer Conversion

• Cost per m²: £1,800 – £2,500
• Why the range: A simple rear dormer on a semi-detached house sits at the lower end. A complex L-shaped dormer on a terraced property with multiple Velux windows pushes toward the top.

Dormers are the most popular option in the UK because they offer the best balance of added space, cost, and planning simplicity. Most dormers fall within permitted development rights.

Hip-to-Gable Conversion

• Cost per m²: £2,000 – £2,800
• Why the range: This involves significant structural work — removing the hip rafters, building a new gable wall, and potentially extending the ridge. Costs rise if the property has a complex roof plan or requires steel supports.

Hip-to-gable conversions are common on 1930s semi-detached homes where the side hip roof limits usable space.

Mansard Conversion

• Cost per m²: £2,200 – £3,000
• Why the range: A full mansard replaces the entire roof structure. The lower end applies to a single-slope mansard with standard finishes. The upper end includes both front and rear mansards, high-end materials, and complex steelwork.

Mansards are most common in London, where maximising every square metre delivers strong returns. They typically require full planning permission.

Room-in-Roof (Shell)

• Cost per m²: £1,200 – £1,800
• Why the range: A shell conversion includes structure, insulation, electrics, and plastering — but no flooring, decoration, or fixtures. The lower end applies to simple trussed roofs with straightforward access. The upper end covers complex structural changes and dormer construction.

What Is Included in the Per-m² Price?

When a builder quotes £2,000 per m², they usually mean the following is included:

• Structural work: Altering or reinforcing roof trusses, installing steel beams, dormer construction
• Insulation: Floor, wall, and roof insulation to meet Part L building regulations
• Electrics: Lighting, sockets, smoke alarms, and extractor fans
• Windows: Velux or dormer windows, including flashing and installation
• Plastering: Plasterboard and skim finish to all walls and ceilings
• Flooring: Joist reinforcement and subfloor (finish flooring may be extra)
• Staircase: A standard straight staircase from the floor below
• Plumbing: Basic radiator installation (bathroom plumbing is extra)
• Scaffolding: External access for the duration of the build
• Waste removal: Skip hire and disposal of construction waste

Always ask for a written schedule of works. Some builders exclude scaffolding or waste removal from their per-m² rate, which can add £2,000–£4,000 to the final bill.

What Is NOT Included?

The per-m² construction cost does not cover everything. Budget separately for:

On a typical £60,000 conversion, these extras can add £12,000–£20,000. That is why the total project cost is often 20–30% higher than the headline per-m² construction rate.

Regional Price Variations per m²

Labour and material costs vary significantly across the UK. Here is what the same £2,000/m² national average looks like in different regions.

London

London's premium reflects higher labour rates, expensive scaffolding permits, congestion zone charges for material deliveries, and strong demand. Boroughs like Kensington & Chelsea and Westminster also have stricter planning requirements, which can extend timelines and add professional fees.

South East England

Surrey, Berkshire, and Buckinghamshire sit just below London but still carry a 20–30% premium over the national average. The high concentration of commuter families drives demand for extra bedrooms and home offices.

Midlands & North of England

Cities like Manchester, Birmingham, Leeds, and Sheffield benefit from a competitive builder market and lower living costs. A 30 m² dormer in Manchester might cost £48,000–£67,000 compared to £54,000–£75,000 nationally.

Scotland & Wales

Scotland and Wales offer competitive pricing, but the planning process differs. In Scotland, most loft conversions require a building warrant and planning permission in practice, which adds £500–£1,500 in fees but does not significantly affect the construction cost per m².

Sources: FMB Regional Pricing Survey 2026; Checkatrade Cost Guides.

Factors That Increase Cost per m²

Several design and site-specific factors push your project toward the upper end of the price range.

1. Roof Trusses

Homes built after 1965 typically have prefabricated trussed rafter roofs. Converting these requires cutting and reinforcing the trusses, which adds £3,000–£8,000 to the structural work. Traditional cut roofs are simpler and cheaper to convert.

2. Staircase Complexity

A straight flight staircase costs £1,000–£2,500. If your loft requires a spiral staircase, a mid-landing turn, or relocation of an existing wall, expect £3,000–£7,000. Terraced houses often have limited landing space, which complicates staircase design.

3. Plumbing and Drainage

Adding a bathroom or en-suite adds £5,000–£12,000 depending on how far the soil pipe must travel. If the soil pipe needs to drop through the floor below, you may need to create a boxed-in section or alter ceilings, which adds labour and materials.

4. Party Wall Matters

If your home is attached to a neighbour, the Party Wall etc. Act 1996 applies. You must notify adjoining owners, and if they dissent, you need a party wall award. This costs £700–£2,000 per neighbour and can delay the project by 4–8 weeks.

5. Conservation Areas and Listed Buildings

If your property is in a conservation area or is listed, you will need full planning permission and possibly heritage consent. This adds professional fees, extends the timeline, and may restrict materials — for example, requiring slate rather than synthetic tiles.

6. Access Constraints

Narrow streets, limited parking, or rear-access-only properties increase scaffolding costs and make material deliveries harder. In central London, some projects require crane hire for steel beams, which can add £1,500–£3,000.

How to Reduce Your Cost per m²

1. Keep the Design Simple

A single dormer is cheaper per m² than multiple small dormers. A straight staircase is cheaper than a spiral. Every design complication adds labour and material cost.

2. Use Standard Windows and Materials

Bespoke roof windows and imported finishes look impressive but inflate costs. Standard Velux windows and British-made materials offer excellent performance at a lower price point.

3. Opt for a Shell Build

A shell-only conversion reduces the per-m² cost to £1,200–£1,800. You handle the interior fitting yourself, spreading costs and potentially saving £5,000–£15,000.

4. Get Multiple Quotes

The FMB recommends three detailed quotes as a minimum. On a £60,000 project, the difference between the lowest and highest quote can be £12,000–£18,000.

5. Check Permitted Development First

If your conversion falls within permitted development, you avoid the cost and delay of a full planning application. Our platform checks this instantly for your address — start with a free render.

6. Book in the Off-Season

Builders are quieter in January and February. Booking during these months can secure a 5–10% discount compared to the spring and summer rush.

Comparing Loft Conversion vs. Extension per m²

Homeowners often weigh a loft conversion against a ground-floor extension. Here is how the per-m² costs compare.

Loft conversions are generally cheaper per m² because they avoid foundation work, drainage alterations, and garden disruption. They also retain your outdoor space — a major advantage in urban areas.

For a full cost breakdown of other extension types, see our extension cost guide.

Getting an Accurate Quote

The per-m² figures in this guide are a solid starting point, but every project is unique. The most reliable way to budget is to get a detailed, itemised quote based on your specific property.

Traditional routes involve months of architect drawings, planning searches, and builder visits. Our platform compresses this into minutes.

How it works:

1. Enter your address on our free render tool
2. Our AI analyses nearby approved planning applications to understand what your local council permits
3. You receive an instant render, floor plan, and cost estimate based on real local precedents
4. Upgrade to our Concept Package for three renders, full plans, and a revision within 48 hours (£495–£995)
5. Or choose Design + Planning for the full planning application, building regulations, and structural engineering (£2,495)

No appointments. No waiting. No guesswork.

Get your free loft conversion cost estimate →

Frequently Asked Questions

What is a good cost per m² for a loft conversion in the UK?

A reasonable benchmark in 2026 is £1,800–£2,200 per m² for a mid-range dormer conversion with standard finishes. Basic Velux conversions start at £1,500/m², while premium mansards can reach £3,000/m². (Source: Checkatrade, FMB)

Why do loft conversion costs vary so much per m²?

Variation comes from conversion type, roof structure, location, finish quality, and site access. A simple Velux in the North of England costs far less than a mansard in central London with bespoke finishes and complex steelwork.

Is the cost per m² figure inclusive of VAT?

Most builder quotes are inclusive of VAT at 20%. However, some smaller firms may quote excluding VAT. Always confirm whether the per-m² rate includes VAT before comparing quotes.

Does cost per m² include design and planning fees?

No. The per-m² figure typically covers construction only. Design fees, planning applications, building regulations, and professional services add 15–20% on top. Our Design + Planning package bundles these for a fixed £2,495.

How do I calculate the total cost from cost per m²?

Multiply the cost per m² by the usable floor area of your converted loft. For example, a 25 m² dormer at £2,000/m² equals £50,000 in construction costs. Then add 15–20% for fees and contingencies, giving a total budget of £57,500–£60,000.

What is the cheapest cost per m² achievable?

A shell-only Velux conversion in a low-cost region can reach £1,200–£1,400 per m². However, this excludes all interior fitting, flooring, and decoration. Be cautious of quotes below £1,200/m² — they may indicate corner-cutting or unqualified labour.

Does adding a bathroom change the cost per m²?

Yes. A bathroom adds £5,000–£12,000 to the total, which on a 25 m² conversion increases the effective cost per m² by £200–£480. Complex plumbing runs push this toward the upper end.

How does London compare to the rest of the UK per m²?

London costs 30–50% more per m² than the national average. A dormer conversion that costs £2,000/m² in Leeds might cost £2,600–£3,000/m² in London due to labour premiums, access constraints, and higher material costs.

Can I get a fixed price per m² from a builder?

Some builders offer fixed-price contracts based on a per-m² rate, but most prefer detailed quotes based on drawings. A fixed per-m² rate can work for straightforward projects but may exclude extras like unforeseen structural work. Always read the contract carefully.

How does a loft conversion cost per m² compare to an extension?

Loft conversions are typically 10–20% cheaper per m² than ground-floor extensions because they avoid foundation work and ground drainage. A loft conversion averages £1,500–£2,500/m², while a rear extension runs £1,800–£2,800/m².

What hidden costs push up the per-m² price?

Unseen roof trusses, asbestos removal, rot damage, party wall agreements, and access difficulties can all add unexpected costs. A 10–15% contingency fund is essential. Our free render tool flags common local issues before you commit.

Is a shell-only conversion worth it for a lower per-m² cost?

A shell conversion reduces the per-m² cost by £300–£600 but leaves you with unfinished space. It is a good option if you are handy, want to spread costs, or have a clear vision for the interior. Most homeowners prefer a full finish for convenience and speed.