Loft conversion cost UK: how much does a loft conversion cost in 2026?

A loft conversion in the UK costs between £55,000 and £208,000 in 2026, depending on the type. A basic rooflight conversion starts from £55,000, a rear dormer from £83,000, hip-to-gable from £86,000, and a full mansard from £143,000. In London, expect to pay 20-40% more than the national average. Professional fees (architect, structural engineer, planning, building control, party wall) typically add £8,000 to £20,000 to the total.

How much does a loft conversion cost in 2026? If you are researching loft conversion cost in the UK, the short answer is £55,000 to £208,000 depending on the type you choose. A loft conversion (sometimes called an attic conversion) is one of the most cost-effective ways to add space to your home. Unlike house extensions, it uses the structure you already have - the roof - turning wasted attic space into a bedroom, home office, or bathroom without sacrificing garden space.

But the loft conversion price can vary enormously depending on the type of conversion, the size of your loft, and where in the UK you live. This guide gives you real 2026 prices based on our project data, breaks down every cost of loft conversion you need to budget for, and explains which type of conversion suits different house types and budgets.

Loft Conversion Costs by Type

The type of loft conversion you choose has the single biggest impact on cost. Here are the four main options, with 2026 prices:

These loft conversion costs include structural work, insulation, plastering, electrics, plumbing for a basic en-suite, staircase, and finishing. They exclude professional fees, which are covered separately below. Note that the attic conversion cost for a basic rooflight is significantly lower than a full structural dormer, so choosing the right type for your property is the most important budgeting decision you will make.

Rooflight (Velux) Conversion

A rooflight conversion is the simplest and most affordable option. It works within the existing roof structure, adding skylights for natural light without altering the roofline. This type is ideal for lofts that already have adequate head height (2.2 m or more at the ridge).

Best for: Homes with a steep roof pitch, budget-conscious projects, home offices or spare bedrooms where maximising every inch of floor area is less critical.

Typical cost: £55,000 - £83,000

Dormer loft conversion cost: £83,000 to £143,000

A dormer extends outward from the sloping roof, creating a box-shaped addition with a flat roof and vertical walls. This dramatically increases usable floor area and head height. The dormer loft conversion cost starts from £83,000, making it a mid-range option. A rear dormer is the most common choice because it usually falls within permitted development rights, meaning you may not need planning permission.

Best for: Most house types, especially terraced and semi-detached homes. It is the most popular conversion type in the UK.

Typical dormer loft conversion cost: £83,000 - £143,000 (L-shaped dormer: £110,000 - £182,000)

Hip-to-Gable Conversion

A hip-to-gable conversion extends the sloping (hipped) side of the roof to create a vertical gable wall, then typically adds a rear dormer too. This is the go-to option for 1930s semi-detached houses and detached homes with hipped roofs that otherwise lose too much space to slopes.

Best for: Semi-detached and detached houses with hipped roofs, especially 1930s and 1950s properties.

Typical cost: £86,000 - £146,000

Mansard Loft Conversion

A mansard conversion replaces one or both roof slopes with a near-vertical wall (typically 72-degree angle) and a flat roof on top. It provides the maximum possible space but involves the most structural work and almost always requires full planning permission.

Best for: Period properties, terraced houses in London and other cities where ground-floor extensions are not possible, and homeowners who want to maximise space regardless of cost.

Typical cost: £143,000 - £208,000

Want to see real examples? Browse our loft conversion portfolio to see completed projects with before-and-after photos.

Factors That Affect Loft Conversion Cost

Two identical-looking houses on the same street can have loft conversion quotes that differ by tens of thousands of pounds. Understanding these factors is essential when estimating the cost of loft conversion for your specific property. Here are the main factors that move the loft conversion price:

Location

Labour and material costs vary significantly by region. London prices are typically 20-40% higher than the national average due to higher labour rates, access challenges, and stricter planning environments. The South East is 10-20% above average, while the North and Midlands tend to be closer to the lower end of the ranges in this guide.

Size and Complexity

A straightforward rectangular dormer on a standard Victorian terrace is very different from an L-shaped dormer on an Edwardian semi with a complex roof structure, chimney stacks, and shared party walls. More structural steelwork, more scaffolding complications, and more bespoke joinery all push costs up.

Specification and Finish

The base costs above include a standard finish: plastered walls, basic en-suite, carpet, and painted surfaces. The loft conversion price rises significantly when you upgrade to underfloor heating, a higher-spec bathroom, built-in storage, or premium flooring - these additions can add £13,000 to £39,000 to the total.

Structural Requirements

Some lofts need more structural intervention than others. If your floor joists need full replacement rather than just reinforcement, or if a steel beam has to span a long distance to support the new structure, this adds cost. A structural engineer will assess this during the design stage.

Access and Staircase

The staircase location affects both cost and how much space you lose on the floor below. Positioning the staircase above the existing one is the most efficient option. If the layout requires relocating rooms or losing a bedroom on the floor below, this creates additional building work and cost.

Loft Conversion Cost in London

If you are searching for loft conversion cost UK figures specifically for London, expect to pay significantly more than the national average. London consistently sits at the top of UK construction costs. Based on our recent project data, here are typical 2026 loft conversion prices for London:

London prices are higher because of several compounding factors: skilled tradespeople command higher day rates, parking and access in dense urban areas add logistical cost, many London boroughs have stricter planning and conservation requirements, and skip and material delivery costs are significantly higher than suburban or rural areas.

If you are planning a loft conversion in London, we recommend getting an accurate quote based on your specific property. See our loft conversion service page for examples of our London projects, or contact us directly to request a consultation.

Professional Fees Breakdown

On top of the build cost, you need to budget for several professional fees. These are often overlooked when people ask how much does a loft conversion cost, but they can add £8,000 to £20,000 to your total loft conversion cost.

Architectural and Design Fees

An architect or architectural designer will produce the drawings you need for planning applications and building regulations. Expect to pay £4,000 to £8,200 depending on the complexity. This usually covers initial design, planning drawings, and building regulation drawings. Some firms include structural engineering calculations in this fee; others charge separately.

Planning Fees

Many loft conversions fall under permitted development and do not need a full planning application. However, you should still apply for a Certificate of Lawful Development (£103 in England as of 2026) to have proof the work is permitted. If you do need full planning permission - for a mansard, or in a conservation area - the application fee is approximately £210.

Structural Engineer

A structural engineer designs the steelwork and specifies how the existing structure needs to be reinforced. This is a non-negotiable requirement for any loft conversion. Fees typically range from £1,300 to £3,250.

Party Wall Agreements

If your loft conversion affects a shared wall (terraced or semi-detached houses), you are legally required to serve a Party Wall Notice on your neighbours under the Party Wall etc. Act 1996. If your neighbours consent, there is no surveyor fee. If they dissent, you will need to appoint a party wall surveyor (£1,300 to £2,000 per neighbour). In the worst case with two dissenting neighbours, this can reach £4,000.

Building Control

Building control inspections are mandatory. You can use your local authority building control service or an approved inspector. Fees range from £800 to £1,600 depending on the project size and your location.

You can find a qualified surveyor through the Royal Institution of Chartered Surveyors (RICS) directory, or ask your architect for recommendations.

Is a Loft Conversion Worth It? Value Added to Your Home

A loft conversion is widely regarded as one of the best-value home improvements you can make. Industry data consistently shows that a well-executed loft conversion adds 15-25% to the value of a property, and in some parts of London and the South East, the return can be even higher.

For a property worth £500,000, a dormer loft conversion costing £104,000 could add £75,000 to £125,000 to the sale price - and you get to enjoy the extra space while you live there. The return on investment is strongest when the conversion adds a genuinely usable bedroom with an en-suite, as this moves the property into a higher bedroom-count bracket on property portals like Rightmove and Zoopla.

Pro Tip: Maximise Your Return

Adding an en-suite bathroom and ensuring the room has adequate natural light and head height are the two things that make the biggest difference to how estate agents value the additional space. A loft room that feels like a proper bedroom - not just converted attic space - commands a much higher premium. See examples of high-quality finishes in our portfolio.

How to Budget for a Loft Conversion

Whether you are planning a simple attic conversion or a full mansard, we recommend budgeting your loft conversion cost in three tiers: the build cost, professional fees, and a contingency.

Build Cost

This is the main construction contract, covering structural work, insulation, electrics, plumbing, plastering, staircase, and basic finishing. Refer to the pricing tables above for your conversion type. The loft conversion cost UK-wide ranges from £55,000 for a rooflight to £208,000 for a mansard.

Professional Fees

Budget £8,000 to £20,000 for architect, structural engineer, planning, building control, and party wall (if applicable). These are detailed in the section above.

Contingency

Always add a contingency of 10-15% to cover unexpected costs. The total cost of loft conversion can increase due to common surprises such as additional structural work once the roof is opened up, upgrading the existing electrical consumer unit to current regulations, or asbestos removal in older properties. A 10% contingency on a £104,000 project means setting aside an additional £10,400.

Payment Timeline

Most loft conversion contractors use staged payments tied to project milestones: a deposit at contract signing (typically 10-15%), then payments at key stages such as steel installation, first fix, second fix, and completion. Never pay the full amount upfront, and ensure all payment terms are documented in your contract. The Federation of Master Builders recommends agreeing a written schedule of payments before work begins.

Why Have Loft Conversion Costs Increased?

If you have been comparing prices to quotes from a few years ago, you will have noticed a significant increase. Several factors are driving this. Material costs rose sharply during 2021-2023 due to post-pandemic supply chain disruptions and have remained elevated, particularly for timber and steel. Skilled labour shortages in the UK construction industry continue to push trade rates higher. Changes to Building Regulations - including stricter energy efficiency requirements from Part L updates - mean better (and more expensive) insulation and ventilation systems. The positive side of these regulation changes is that your new loft space will be more energy-efficient and comfortable than conversions built to older standards.

Loft Conversion vs Extension vs Attic Conversion: Cost Comparison

Many homeowners compare the cost of loft conversion with other ways to add space. Here is how the main options compare on price per square metre in 2026:

The attic conversion cost is the lowest of any option because it requires no structural changes to the roofline. A dormer loft conversion costs more per square metre but delivers significantly more usable floor area. Both options compare favourably with house extensions, and they do not reduce your garden space. For a full home renovation that includes a loft conversion, talk to our team about combined project pricing.

Frequently Asked Questions

Do I need planning permission for a loft conversion?

Most loft conversions on houses (not flats or maisonettes) fall under permitted development rights and do not require a planning application. Exceptions include mansard conversions, properties in conservation areas, and any conversion that exceeds permitted development volume limits (40 m³ for terraced houses, 50 m³ for detached and semi-detached). Even if you do not need planning permission, always apply for a Certificate of Lawful Development as proof.

How long does a loft conversion take?

A typical loft conversion takes 8-12 weeks from start to completion on site. The design and planning stage before building work begins usually adds 4-8 weeks. A straightforward rooflight (attic conversion) may be faster at 6-8 weeks, while a complex mansard can take 12-16 weeks.

Will a loft conversion add value to my house?

Yes. A loft conversion typically adds 15-25% to the value of a property, making the cost of loft conversion one of the best returns on any home improvement. The exact increase depends on the quality of finish, whether an en-suite is included, and local property values.

Can all lofts be converted?

Most lofts can be converted, but some are more straightforward than others. The key measurement is the head height at the ridge: you generally need at least 2.2 m from the top of the existing ceiling joists to the underside of the ridge beam. If your loft has less than this, options like a dormer or mansard can create the necessary height, but at additional cost. A RICS-accredited surveyor or architect can assess feasibility during an initial visit.

What is included in a loft conversion quote?

A comprehensive quote should include: scaffolding and access, structural steelwork, roof alterations, floor reinforcement, insulation (thermal and acoustic), staircase, electrics, plumbing (if en-suite included), plastering, and basic decorating. Always check what is excluded - common exclusions are professional fees, party wall costs, building control fees, and final decoration or flooring.

Do I need a party wall agreement?

If your conversion involves work on or near a shared wall (typical for terraced and semi-detached houses), you are legally required to serve a Party Wall Notice on your adjoining neighbours. This is a requirement of the Party Wall etc. Act 1996. If your neighbours agree, no surveyor is needed and there is no additional cost. If they dissent, both parties need surveyors, which adds cost (see Professional Fees above).

How much does a loft conversion cost for a bedroom with en-suite?

A loft conversion that creates a bedroom with en-suite bathroom typically costs £83,000 to £143,000 for a dormer, or £55,000 to £83,000 for a rooflight conversion (if there is sufficient head height). The en-suite itself adds approximately £5,000 to £15,000 to the loft conversion price depending on specification. This is the most popular configuration and delivers the strongest return on investment when you sell.

How do I choose a loft conversion company?

Look for a company that specialises in loft conversions rather than a general builder. Check that they have relevant insurance (public liability, employer's liability, and contract works insurance), ask for references from recent projects, and verify their membership in trade bodies such as the Federation of Master Builders. Ask to visit a completed project if possible, and always get at least three detailed quotes before making a decision.

 

Ready to Get an Accurate Quote?

Every loft is different. The prices in this guide give you a solid starting point, but the only way to get an accurate cost for your specific property is with a professional survey and detailed quote. houseUP is a London-based construction company specialising in loft conversions, extensions, and whole-house renovations. Get in touch for a free consultation and quote tailored to your project.