What Does a Loft Conversion Cost?

At TrustedBuilders, we've collected price data from completed projects and industry data. When it comes to converting a raw loft into habitable space, we see that the average price in the UK is approximately £1,500 to £2,000 per square metre.

This includes all costs associated with the project; both materials and labour. However, we see that some projects become significantly more expensive, up to £3,000 per square metre, particularly in London and the South East. 

Others are more affordable (typically when only simpler measures are needed), down to around £1,200 per square metre. 

According to recent UK construction industry data, the national average for a standard loft conversion ranges from £40,000 to £60,000, though this varies widely depending on property type, location, and specification.

Why Convert Your Loft?

There are several compelling reasons to convert your loft. As time passes, our needs change, and many homeowners find they've outgrown their homes, especially with the recent trend toward working from home creating demand for home offices. 

Moving house is expensive, with stamp duty, legal fees, and estate agent commissions. A loft conversion could typically add 10-20% to your property's value, making it not just a lifestyle improvement but possibly a sound financial investment as well.

With an extra floor, you can create much-needed additional space – whether that's a master bedroom with en-suite, a home office, a playroom for children, or even a self-contained living area for an elderly parent or returning adult child.

An Example: Converting a Raw Loft in a Detached House

To provide an understanding of what the various parts of a loft project cost, we've included a quote for converting a raw loft below. 

This project involves converting approximately 40 square metres of floor space in a detached house in South East England. Note that all projects are different, so the example is only meant as an indication of where you might end up. This example does not include establishing a kitchen or bathroom in the loft, which keeps the price down.

• Carpentry and building work (including structural reinforcement, insulation, new staircase, walls, ceilings, floors): £38,000
• Electrician (including new consumer unit and wiring): £6,500
• Plumbing (radiators and pipework): £3,200
• Painter and decorator: £5,300
• Windows and roof lights: £4,800
• Site setup, skip hire, scaffolding and project management: £7,200

Total: £65,000

The price ends up at approximately £1,625 per square metre of floor space. In London, the same project would likely cost 20-30% more due to higher labour rates and additional logistics costs.

Saving Money

There are several steps you can take to make the project more affordable. The most obvious is doing parts of the job yourself, though be aware that most structural work must be certified by qualified professionals to comply with Building Regulations.

Depending on your skills and experience, decorating, laying wooden flooring, or installing skirting boards might be tasks you can handle.

Also consider what is actually necessary for your needs. Hiring an architect or architectural technician (typically costing between £1,000-£3,000 for loft conversion plans) will likely provide valuable input early in the process about what is really needed. These professionals can help find space-efficient solutions that reduce costs. 

If you want a bathroom in the loft, you can save significantly by placing it directly above an existing bathroom. This reduces the amount of pipework needed and simplifies waste connections. 

Can I Convert My Loft?

First and foremost, you must investigate what possibilities you have under England's planning laws and building regulations. Most loft conversions can fall under "Permitted Development" rights, which would mean you don't need planning permission. However, these are loft conversions that adhere to strict criteria.

For your loft conversion to fall under PD, it needs to stay within certain parameters. First and foremost, it’s required that the house ”Is not a building containing one or more flats, or a flat contained within such a building

• Has not already had additional storeys added to it under permitted development rights
• Was not changed to be used as a house (from a previous non-residential use) under permitted development rights.
• Was not built as a ‘New Dwellinghouse’ under permitted development rights.
• Is not on Article 2(3) designated land”.

In regards to the planned loft conversion, some of the requirements are that:

• “Materials must be similar in appearance to the existing house
• Volume of enlargement (including any previous enlargement) must not exceed the original roof space by more than:
• 40 cubic metres for terraced houses; or
• 50 cubic metres otherwise
• Must not exceed the height of the existing roof.
• On the principal elevation of the house (where it fronts a highway), must not extend beyond the existing roof slope.
• Must not include:
  
  • verandas, balconies or raised platforms; or
  • installation, alteration or replacement of any chimney, flue, or ‘soil and vent pipe’
• Side-facing windows must be obscure-glazed; and, if opening, to be 1.7 metres above the floor of the room in which they are installed.
• Construction must ensure that:
  
  • The eaves of the original roof are maintained (or reinstated)
  • Any enlargement is set back, so far as practicable, at least 20cm from the original eaves 
  • The roof enlargement does not overhang the outer face of the wall of the original house”

Note that these are not the only requirements - there are more, and there may also be unique requirements for your area. Article 4 Directions may remove or restrict permitted development rights locally, for example. Always check locally, and when in doubt, ask. 

Also, this information is from 2025 - always verify that you use the latest, updated information, which you’ll find on sites such as Planning Portal. 

Conservation Area

If you live in a conservation area, a listed building, or an area of outstanding natural beauty, you will likely need planning permission. 

Similarly, if your plans include altering the roof height or adding a dormer that significantly changes the appearance of your house, planning permission will likely be required. If the house is listed, you will need Listed Building Consent, which is separate from planning permission.

In all cases, Building Regulations approval is mandatory to ensure structural stability, fire safety, energy efficiency, and safe access.

Technical Limitations and Party Wall Act

Technical limitations related to water pressure, electrical capacity, and structural integrity must also be addressed.

Building standards require that unless your existing structure is dimensioned for the extra weight, you must reinforce the load-bearing elements throughout the house – typically involving the installation of steel beams or improved joists that meet current British Standards.

For terraced or semi-detached houses, you'll likely need to provide a written Party Wall Notice and a Party Wall Agreement with your neighbours, as per the Party Wall Act 1996.

All in all, there are many legal and practical considerations when converting your loft. The process starts with thorough planning and professional guidance.

Getting Your Loft Conversion Approved

There are numerous regulations you must follow to get a space approved for habitable use, and professionals have comprehensive knowledge of these requirements. These rules can be complex, with various exceptions and additional considerations depending on your property type and location.

One example is ceiling height: Although a height of 2.2 metres is permitted, a height closer to and exceeding 2.4 meters is highly recommended in terms of comfort. For the staircase, you need a minimum headroom of 2 metres, though in some cases, this can be reduced to 1.9 metres. The regulations also require sufficient natural light and adequate ventilation.

Fire Safety 

Fire safety is another crucial consideration. What manner of fire safety features are required depends on your property and the number of storeys, meaning a loft conversion can trigger different requirements for fire safety features. See Document B for specific requirements. 

These are some of the requirements you must meet to get the loft approved for permanent habitation. Additionally, there are several documents and approvals that must accompany the application. It is quite a job to complete the application with all the necessary papers, and a profession will therefore be of great help to you. 

Plan Well

A good planning process is crucial when converting a loft, as this is where you lay the foundation for the entire project. It is always advantageous to start early – ideally 6-12 months before you want construction to begin. This allows time for obtaining necessary approvals, which in the UK can include:

• Planning permission (if required)
• Building Regulations approval
• Party Wall Agreements with neighbours. 

Planning ahead also helps you adapt to challenges that might arise, such as unexpected structural issues or delays in the council's planning department.

Architect

It is wise to find an architect or architectural technician who can design your loft conversion as early as possible. In the UK, you can expect to pay anywhere from £1,000 to £3,000 for professional drawings, depending on the complexity of your project. The architect can guide you through UK planning regulations and provide valuable advice on interior design and floor plans. 

Although it might seem like an unnecessary expense to some, setting aside 3-5% of your budget for design services will often pay off when it comes to the final result. It represents a relatively small portion of the total costs, and a professional will find solutions and opportunities you might not have considered.

Design Your Loft Conversion

UK loft spaces offer unique design challenges and opportunities, such as dormer windows, roof lights, sloped ceilings, and truss constraints. A qualified architect will help you maximise natural light and make the most of limited space while meeting all regulatory requirements. Additionally, they can help you navigate the sometimes complex process of applying to your local council for necessary permissions.

Find The Right Tradespeople

Converting a loft from raw space to habitable area requires specific expertise, as there are elements that differ significantly from other home improvement projects. In particular, there are challenges related to complying with UK Building Regulations, structural modifications, fire safety provisions, staircase regulations, and energy efficiency requirements that are specific to loft conversions.

For structural work, you'll need contractors familiar with the typical UK housing stock – from Victorian terraces with their load-bearing walls to more modern properties with trussed rafters that require careful reconfiguration.

A qualified structural engineer (costing £500-£1,500) should always be consulted to prepare calculations and drawings that satisfy Building Control requirements. For electrical work, you'll need a qualified electrician, preferably one registered with a competent person scheme such as NICEIC or NAPIT who can self-certify their work.

If your conversion includes a bathroom, your plumber should be familiar with loft specific challenges and various solutions available under UK water regulations. Energy efficiency is also important.

For loft conversions in terraced houses or flats, the work requires particular expertise in dealing with party walls and shared roof structures, as well as sound insulation that meets Building Regulations Part E. These projects often require contractors with experience in navigating the Party Wall Act 1996 and the specific challenges of working in densely populated urban areas with restricted access.

To help you make an informed choice, we at TrustedBuilders have vetted skilled and experienced UK contractors who specialise in loft conversions. If you register your project on our website, we'll connect you directly with contractors who have proven track records, and excellent references from similar loft conversion projects in your area.

Choice of Contract Type

There are mainly two different forms of contract you can choose between for your loft conversion: a main contractor arrangement or a self-managed project. What suits you best depends on your experience, time availability and risk tolerance, but for most UK homeowners, working with a main contractor is the preferred option.

One Main Contractor

With a main contractor arrangement, you engage one company – typically a specialist loft conversion firm or a general building contractor – who then sources and manages all the necessary subcontractors. You have a single point of contact for the project.

The main contractor takes responsibility for ensuring that everything complies with Building Regulations, is completed on time, and stays within the agreed budget. The contractor will typically be responsible for arranging Building Control inspections at key stages of the project.

When you choose this arrangement, you may pay a premium of around 15-20% on overall costs, but the contractor assumes responsibility for coordinating the various trades and resolving any issues that arise.

The main contractor should also have appropriate insurance in place, including public liability insurance and employer's liability insurance, which are legal requirements in the UK. This approach offers significant peace of mind, especially given that loft conversion projects can uncover unexpected issues once work begins.

Create A Budget, Progress Plan and Contracts

There is much to keep track of when managing a loft conversion in the UK, and for someone not used to leading construction projects, it's easy for things to get a bit out of hand. 

A detailed budget is essential to maintain control throughout the process. Beyond the basic construction costs, UK homeowners need to budget for several specific expenses in addition to labour and materials: 

• Building Regulations application fees 
• Planning permission if required 
• Structural engineer's fees
• Party wall surveyor fees if applicable 
• A contingency fund.

Industry best practice in the UK is to allocate 10-15% of your total budget as a contingency for unforeseen issues, which are not uncommon in loft conversions of older properties.

These might include structural problems that only become apparent once work begins, issues with the existing roof covering, or electrical rewiring requirements. By having this buffer built into your budget from the start, you'll be better prepared for unexpected costs.

Contract

It is advantageous for both you and your contractor to have absolute clarity on what will be done. Using a standard form of contract such as the JCT Minor Works or the FMB contract provides a framework that protects both parties.

These contracts should include detailed specifications covering materials, finishes, and quality standards. In the UK, this detailed specification is often called a "Schedule of Works" and serves as a reference point throughout the project. 

For consumer protection, ensure your contract includes clear payment terms – the standard approach in the UK is stage payments linked to completion of specific phases rather than calendar dates. Also make sure the contract specifies a defects liability period (typically 6-12 months) during which the contractor is responsible for rectifying any issues.

How Long Does a Loft Conversion Take?

A well-structured timeline is equally important. Loft conversionstypically take 6-12 weeks depending on complexity, but this can extend if you're adding a bathroom or need specialized structural work. Respectable contractors will provide a project timeline showing key milestones. This should include scheduled building bontrol inspections at critical stages. 

Remember to get a completion certificate, which confirms adherence to building control regulations, from building control, or an approved inspector, at the end, as well as all documentation from your tradespeople.

The completion certificate is a formal document which confirms that your conversion complies with legal requirements, and may be required from your insurance or mortgage lender. It will also come in handy the day you decide to sell your home.

If you wish to get in touch with quality-assured contractors for your loft conversion project, you can register on TrustedBuilders, and we will connect you with vetted professionals who understand UK building standards and regulations.

Our network includes contractors who are members of recognized trade associations such as the Federation of Master Builders, providing additional peace of mind through their dispute resolution services and warranty schemes.