The average dormer loft conversion
cost in the UK is between £30,000 and £45,000
Pricing guides

How much does a dormer loft conversion cost?

The most popular and versatile type of loft conversion, a dormer conversion is essentially a box structure with windows built into a pitched roof. A dormer loft conversion is a great way to maximise the space in your home, and potentially add value to it too. There are several types of dormer loft conversions, including L-shaped, rear, side, full-width and double. But how much can you expect to pay for each? In this handy guide, we break down the costs involved. 

The cost of a dormer loft conversion in the UK varies on average between £30,000 and £45,000 depending on the size of the conversion, the quality of finish, the size of the property, the area of installation and the ease of access. Here, find out how the costs break down and where you can save money. Note that prices are current as of 2024. 


Average dormer loft conversion costs

There are many different costs involved in a dormer loft conversion, from the structural work through to the flooring, windows and insulation.

Use our handy cost calculator to find out how much you can expect to pay for your dormer loft conversion:


Dormer loft conversion jobAverage cost
Dormer loft conversion with a double bedroom£18,000 to £25,000
Dormer loft conversion with a double bedroom and ensuite£30,000 to £35,000
Twin dormer loft conversion£40,000 to £45,000
Dormer bungalow conversion£20,000 to £25,000
Staircase£1,000 to £1,500
Dormer loft windows£250 to £250 each (excluding labour costs)
Loft insulation£550 to £950
Flooring£500 to £800
Bathroom fittings£4,500 to £6,000
Scaffolding£800 to £900 per week
Skip hire£250
Party wall agreement£1,500


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How much does dormer loft conversion labour cost?

A dormer loft conversion involves different tradespeople who will charge different rates. To give you a rough idea, here are some average rates for the different trades involved. Note that prices may be higher in London and the southeast. 

Builder£25 to £35 per hour or £160 to £300 per day
Tiler£25 to £40 per hour
Plumber£35 to £45 per hour
Electrician£55 to £100 per hour
Plasterer£30 to £55 per hour
Decorator£25 to £50 per hour

Cost of loft insulation

A well-insulated loft can make your home more energy efficient and lower your heating bills. The average loft insulation cost is £550 to £960, depending on materials. At the cheap end of the scale, you’ve got blanket loft insulation, at around £5 per m2. At the more expensive end, there’s sheet or foam board insulation, which costs approximately £30 per m².

Cost of windows

Installing windows is a crucial stage in any dormer loft conversion. The average cost of windows measuring 100cm x 100cm (excluding labour) is between £200 and £250. You’ll pay more for large windows and less for smaller ones. Roof windows (often called Velux windows) typically cost between £350 and £500.

Cost of flooring

The cost of the flooring for your new loft space will vary, depending on the type and quality you choose. At the budget end of the scale, there is vinyl flooring at between £15 and £25 per m². Wood typically costs £30 to £80 per m², while carpet is between £10 and £65 per m². For tiled flooring, for example in a bathroom, you can expect to pay between £60 and £80 per m².

Cost of a staircase

Once the dormer structure is in place, it’s time to install the staircase. There are different options available at different costs:

Staircase typeCost per m²
Basic staircase£1,000 to £1,300
Fixed ladder with banister£200 to £400
Custom-built stairs:£4,000 to £10,000
Spiral staircase£2,500 to £5,000
Alternating tread stairs£400 to £800

Cost of scaffolding

The first step in a dormer loft conversion is erecting scaffolding to give the builders access to your roof. Scaffolding hire usually costs between £800 and £900 per week and your builder will usually include this in their quote for the whole project. 

Cost of Building Regulations

Any type of loft conversion needs to meet Building Regulations to make sure it’s structurally safe. These regulations impact the use of materials, the type of staircase and the overall layout. Your builder is responsible for making sure their work complies with these regulations and for arranging any necessary inspections, but it’s important to check that this is done. Non-compliance can make it difficult to sell your home in the future, and it may even mean that you have to remove the work.

The inspection is usually carried out by your local authority or a building control officer and costs, on average, £500 to £900.

Cost of a party wall agreement 

If you share a wall with one or more neighbours, you will need to draw up a party wall agreement. This requires the use of a party wall surveyor, who typically charge anywhere between £100 and £400 per hour. Your neighbours may be happy to use your surveyor, or they might prefer to use their own, in which case you will need to pay that cost too.

The average cost for getting a party wall agreement for a dormer loft conversion is £1,500.

Cost of an architect

While it’s not essential to use an architect for a dormer loft conversion, they can save you a lot of hassle, and potentially money, further down the line. Lofts are not always first built with future conversion in mind and working in them can therefore prove more complex than it might seem.

If you decide to work with an architect to plan your loft conversion, you can usually expect to pay between £500 and £1,500. Architects usually charge a percentage of the total project cost, so this price will depend on the specifics of your project. 

Cost of structural beams, joists and masonry

If you are looking to source your own materials, the cost of structural elements, like beams, joists and masonry, can vary between £1,500 and £4,000. These costs will usually be included in any quote you receive for the project, however. Bear in mind, too, that your builder can usually secure more competitive trade rates for materials. 

Cost of electrics

Once the external work has been completed on your dormer loft conversion, it’s time to install the electrics. The average cost of fitting and checking electrics in a dormer loft conversion is between £300 and £600. An electrician typically charges between £50 and £110 per hour.

Cost of bathroom fittings

If your dormer loft conversion includes an ensuite bathroom, you’ll need to choose and install a new bathroom suite. These might include a walk-in shower, a bathroom, sink and toilet. Depending on the type and quality of fittings you choose, you can expect to pay between £4,500 and £6,000 for a new bathroom.

Cost of decorating materials

Once the structural work is complete, you’ll need to decorate your new space. This usually involves plastering, painting or wallpapering, fitting skirting and laying carpet or other types of flooring. On average, decorating materials for a dormer loft conversion cost between £800 and £1,000. This doesn’t include the cost of labour.

Cost of built-in storage

Built-in storage like wardrobes, cabinets and shelves can help you make the most of your new space. The cost of this varies depending on the type and quantity of storage you need, but you can generally expect to pay anywhere between £2,000 and £5,000

Cost to hire a skip

Major building work like a dormer loft conversion usually generates a lot of waste, so you’ll need to hire a skip or use waste clearance specialists. The cost of hiring a medium-sized skip is typically in the region of £250.



How long does a dormer loft conversion take?

On average, a dormer loft conversion should take around eight to ten weeks. However, it could take longer if you’re planning a substantial conversion with complex elements. Here are some of the typical timeframes involved in a dormer loft conversion:


Erecting scaffoldingOne day
Opening up roofThree to four days
Dormer constructionOne to two weeks
Fitting windowsOne day
Fitting flooringOne day
Installing staircaseTwo to three days
Installing bathroomFour to five days
Installing electricsTwo to three days
Decorating and finishingThree to four days
DismantlingOne day


How to reduce dormer loft conversion costs

The costs involved in a dormer loft conversion can be daunting, and we recommend doing plenty of research to make sure you’re getting the best value for money at every stage of the project. 

To give you a helping hand, here are a few suggestions for saving money on your dormer loft conversion:

Project-manage the work yourself: You can save money by taking on certain project management aspects of the work, hiring different tradespeople for different elements of the project. However, this can mean more hassle and risk if something goes wrong or if one aspect of the project is running late, which then has an impact on the whole schedule.

Work with trustworthy and reliable tradespeople: The best way to ensure your loft conversion stays within budget and runs to time is to hire reliable and experienced tradespeople who are adept at dealing with any complications and managing successful projects.

Plumb over existing plumbing: Ensuring the plumbing needed in the conversion is placed over plumbing already in your home can help keep the cost of your conversion down. This may require you to adjust the plans, but it eliminates the need for more complex plumbing work.

Complete the finishing work yourself: You can cut down on the cost of your loft conversion if you carry out some of the final elements, like painting and decorating, yourself. If you’re a dab hand at DIY, there’s no reason you shouldn’t take on these parts of the project rather than hiring professional plasterers and painters. Bear in mind, however, that trade professionals may be able to source decorating materials at a cheaper price than you can.

Shop around: Getting a range of quotes means you can find one that fits your budget and gives you peace of mind that you’re getting a fair and competitive price. With MyBuilder, you can post your job for free, and we’ll share it with local builders to give you the best chance of getting a range of quotes for comparison.



What permission do I need for a dormer loft conversion?

If you live in a terraced or semi-detached house and share a wall with a neighbour, you will need a party wall agreement, in which the owners of surrounding properties give you permission to go ahead with construction on the walls that you share.

The party wall agreement is created by a surveyor and a legal professional. Surveyors' rates can vary between £150 and £200 per hour, and a party wall award (with a surveyor included) can cost around £1,000.

Often, house conversions can require planning permission if you live in a restricted area, the price for this being £172 in England.

You may also be required to pay Building Regulations costs to ensure that your conversion complies with existing local laws. The price for this can range from £400 to £800, depending on the project's scale and complexity.

Will a dormer loft conversion add value to my home?

A dormer loft conversion involves a significant initial outlay, but if it’s completed to a high standard, it can add value to your home that more than offsets that cost.

Research has shown that a loft conversion with a double bedroom and bathroom added to a three-bedroom house can add about 20% to its value. That can be even higher in London.

With house prices always liable to fluctuation, however, there is no guarantee that a loft conversion will add overall value. Your priority should always be ensuring the work is of a high quality and fully compliant with Building Regulations, so that you can make the most of it and ensure that there are no issues when you come to resell your home.

Do I need to ask my neighbour for permission before starting a dormer loft conversion?

If you live in a terraced or semi-detached property and share a wall with a neighbour or neighbours, you will need to have a party wall agreement, in which they give their permission for the planned work. This requires you to use a party wall surveyor, and as the homeowner carrying out the work, you’re responsible for the cost. Your neighbour may prefer to use their own surveyor, and if the two parties don’t agree, you might need to get a third surveyor involved, all at your expense.

Even if you don’t share a wall, it’s wise to let neighbours know before starting any major work on your home, as it is likely to be noisy and disruptive, and you may need to take up nearby parking spaces with a skip or contractors’ vehicles.


Your dormer loft conversion checklist

We’ve put together a helpful checklist you can use to make sure you’re well prepared for your dormer loft conversion project.

  • Decide what type of dormer loft conversion you want: There are many different types of dormer loft conversion, and the one you choose depends on the style of your home, the space you have available and your budget. Speak to an architect or a builder for advice on the best option for you.
  • Get the paperwork sorted: If you share a wall with one or more neighbours, you’ll need a party wall agreement. You may also need to apply to Building Regulations. If your home is listed or you live in a conservation area, you’ll need the relevant permissions before you start work. Ask your builder for advice on the type of permission you need.
  • Get the timing right: Carrying out work in the summer means the days are likely to be longer and the weather drier, which will make it easier for tradespeople to get on with work. However, you may find there’s more demand for builders over the summer for that very reason, so it’s worth making enquiries and locking in a date as early as possible.
  • Factor in extra costs: Your overall budget for your loft conversion should include any new fixtures and fittings, as well as extras like scaffolding and skip hire. When you request quotes, make sure that they include every element of the project.
  • Shop around for fair and competitive prices: With MyBuilder, you can contact local builders and request a range of quotes to find one that suits your budget.
  • Choose an accredited and competent builder: At MyBuilder, we check the skills and qualifications of all applicants to our network, so you can be sure we’ll only put you in touch with a builder who has the right skills, qualifications and experience.


Looking for a trustworthy and experienced local builder for your dormer loft conversion? Post your job on MyBuilder, completely for free, and we’ll share it with hundreds of skilled and accredited builders in your area. Check out their experience and reviews and request a quote from anyone that looks suitable for the work.


Get a dormer loft conversion quote

We can help you meet professional dormer loft conversion builders near you to get real quotes today.

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