How Much Does a Loft Conversion Cost in 2026?

The type of conversion is the single biggest factor in the price. Here are typical 2026 build costs:

These are build costs — the construction work itself. Professional fees, planning, and other costs are listed separately below.

A typical loft conversion build quote includes:

• Structural alterations to the roof (new steels, purlins, rafters)
• Dormer construction (if applicable)
• Strengthened floor joists
• New staircase from the floor below
• Insulation (roof, walls, dormer)
• Rooflights or dormer windows
• Internal walls and plastering
• First and second fix electrics
• First and second fix plumbing (radiators or underfloor heating)
• Fire doors on the staircase route (FD30 — required by building regulations)
• Mains-wired interlinked smoke alarms
• Decorating (basic paint finish)

A typical build quote does not include:

• En-suite bathroom fittings
• Flooring
• Built-in storage or wardrobes
• Velux blinds
• Furniture
• Decoration of the rooms below (staircase area, landing, bedroom below)

Most loft conversions include an en-suite shower room. Budget separately for this:

The plumbing first fix (waste pipes, water supply, soil stack connection) is usually included in the builder’s price. The bathroom fit-out (tiles, sanitaryware, fitting) may be separate.

Total professional fees: typically £2,500–£6,000.

Most dormer and Velux conversions are permitted development and do not need a planning application. Mansard conversions and front dormers usually require full planning permission.

Even if your conversion is PD, getting a Lawful Development Certificate (£274) is strongly recommended. It gives you official proof the conversion is lawful — essential when selling.

A rear dormer costing £45,000 in the Midlands might cost £52,000–£58,000 in outer London and £60,000–£68,000 in inner London.

Structural complexity

Roof type matters. A simple gable-to-gable roof (common on terraced houses) is the easiest to convert. Hipped roofs, multiple-pitched roofs, and low-pitch roofs all add cost because they require more structural work.

Steel beams. Most loft conversions need at least one steel beam (RSJ). Complex designs may need several. Each beam typically costs £500–£1,500 installed.

Chimney breasts. If the chimney passes through the loft, you may need to support or remove it. Removing a chimney breast in the loft costs £1,000–£3,000.

Specification choices

Staircase. A standard staircase costs £1,500–£3,000. A bespoke or feature staircase can cost £4,000–£10,000.

Windows. Standard Velux rooflights cost £500–£1,500 each installed. Velux Cabrio balcony windows (which open outward into a mini balcony) cost £3,000–£5,000 each.

Flooring. Engineered oak: £1,500–£3,000 for a typical loft. Carpet: £500–£1,500.

Built-in storage. Fitted wardrobes in the eaves: £1,500–£4,000. This is one of the best investments — the eaves space is otherwise wasted.

Access and logistics

Scaffolding. Required for any dormer. Typically £1,500–£3,000, usually included in the builder’s quote.

Skip hire and waste removal. Budget £500–£1,500 for the project.

Access restrictions. If there is no scaffolding access from the rear (terraced houses with no back lane), costs increase for crane hire or manual handling.

• Fire doors: Every door on the staircase from the loft to the front door must be replaced with an FD30 fire door. Budget £200–£400 per door × 4–6 doors = £800–£2,400
• Smoke alarms: Mains-wired interlinked alarms on every floor. £300–£600 for supply and fit
• Decoration of affected rooms: The staircase installation and fire door fitting will damage decoration on the floor below. Budget £1,000–£2,000
• Temporary disruption: You will lose a bedroom below during the staircase installation (typically 1–2 weeks)
• Building insurance notification: Inform your insurer and update your sum insured after completion
• Increased council tax: A loft conversion can trigger a council tax revaluation when you sell (not while you live there)

For a typical rear dormer loft conversion with en-suite in the Midlands or South:

For London, add 20–40%. For a Velux-only conversion without an en-suite, the total drops to around £28,000–£40,000.

Generally, yes — and it is one of the strongest returns on investment of any home improvement:

• A loft conversion adding a third bedroom to a two-bed house can add 15–20% to the property value
• Adding a fourth bedroom with en-suite to a three-bed house typically adds 10–15%
• In high-value areas, the uplift can significantly exceed the build cost

The return depends on the local market. In areas where bedrooms are the main driver of value (family-friendly suburbs, catchment areas for good schools), loft conversions add the most value.

• Choose Velux over dormer if you have enough headroom. A rooflight conversion avoids the structural cost of building a dormer.
• Keep the en-suite simple. A compact shower room serves the purpose without the cost of a large bathroom.
• Use a specialist loft conversion company rather than a general builder. They do this every day and are often more efficient.
• Get three quotes minimum. Prices vary by 20–40% between companies for the same specification.
• Fix the specification before signing. Changes during the build are the fastest way to blow the budget.
• Do your own decorating. Painting the loft room and the affected areas below can save £1,000–£3,000.

1. Check if your loft conversion is permitted development using our free PD checker
2. Read our loft conversion planning permission guide for PD rules, building regulations, and types of conversion
3. Protect your investment — our PD Certificate Report helps you apply for an LDC