Cost Guides

How Much Does Loft Conversion Cost?

Written by  John Davies
Last updated: August 23, 2023
How Much Does Loft Conversion Cost?

If you need extra living space but don’t want to build an extension or move to another building, loft conversion is the way to go. Moving is like the nuclear option, considering the stress and expenses that come with it. As for a traditional extension, there could be several reasons you don’t want to or aren’t allowed to build it.

But it doesn’t matter how you came about this idea of converting your loft. It is still brilliant. You will be getting that extra space with a view, natural light and an ample supply of vitamin D, which is essential to health and sleep.

Dare I say, “any loft is an ideal location for a home office, study, gym, man-cave, playroom, bedroom or even a bedroom ensuite (for personal use or rental).” And you will be getting it with less financial and time investment than the other two options.

It’s so cheap that sometimes, all you need is to reinforce the ceiling and floor, add windows and stairs, and then paint and decorate. Then you have an extra floor. However, that is only in cases where the loft already has enough headroom. But, even in situations where loft conversion takes more work, it still offers more value for money than moving or building an extension.

Apart from being an affordable way to get extra living space, loft conversion also adds to the financial value of your property. It adds about 15 to 20% more. That puts it in the same league as other valuable home improvement projects like patio and driveway installation and chimney removal.

As for loft conversion prices (the reason why you are here), expect something in the region of £20,000 to £85000 depending on conversion type and other factors that will be discussed soon. However, I must warn you that these are mere estimates, not exact figures. But they will give you ideas of what to expect, so you don’t get taken advantage of.

In fact, by the end of this article, you won’t just know about loft conversion costs. You will also know the types of loft conversion, and supply, labour and additional costs. Basically, everything you need to know about a basic loft conversion project. Let’s get started.

How Much Does the Average Loft Conversion Project Cost?

Loft conversion type20 square metres (£)30 square metres (£)Loft of 40 square metres (£)
Velux roof light loft conversion cost20,000 – 24,00026,000 – 30,00033,000 – 36,000
Dormer loft conversion cost25,000 – 29,00038,000 – 44,00041,000 – 57,000
Hip-to-gable loft conversion cost30,000 – 50,00045,000 – 75,00055,000 – 80,000
Mansard loft conversion cost 45,000 – 50,00055,000 – 60,00065,000 – 85,000

As you can see from Table 1, the prices vary wildly. The biggest factors responsible for this are the size and type of loft conversion. Other cost factors are roof type, materials used and what you want to build the loft into (for example, an office won’t cost as much as a bedroom ensuite).

Loft conversion supply costs

Supply typeBrief descriptionCost (£)
StairsA permanent stairway1,000 – 2,500
StructuralMasonry, joists etc., to build and repair the floors, walls, stairs and roof1,500 – 5,000
WindowsDormer, double glazed, roof lights etc300 – 2,000
LightingCeiling lights, lamps etc40 – 4,000
ElectricityLights, sockets etc300 -600
FlooringTo lay the floors150 – 3,000
BathroomShower, tub, piping etc4,000 – 6,000
Painting and decorationPaint, plaster, wallpaper, furniture700 – 17,000

Cost of specific supplies

Costs of windows

Window typeCost (£)
Velux roof lights300 – 550
Dormer150 – 320

Cost of flooring

Flooring material typeCost per square metre (£)
Wood7 – 60
Vinyl7 – 20
Tile10 – 50
Carpet5 – 50

Lighting costs

Lighting typeCost (£)
Ceiling lights10 – 3,500
Floor and table lamps10 – 3,000
Smart lighting15 – 300

Stairs costs

Stairway typeCost (£)
Basic1,000 – 1,300
Spiral1,000 – 1,500
Custom2,700 – 8,000
Metal1,000 – 3,000
Alternating treads350 – 700
Fixed ladder with bannister150 – 500

From the information in tables 2 to 6, you will realise that supply costs also vary widely. Once again, it depends on the materials you want and choose. However, you can also reduce supply costs by buying them yourself instead of leaving everything to the loft conversion specialists. I suggest finding a loft conversion cost calculator if you want to try this.

Loft conversion labour costs

Table 7: Hourly and daily rates of different labourers/specialists needed for a loft conversion project.

Labour typeHourly rates (£)Daily rates (£)
Builder20 – 35130 – 260
Joiner20 – 40160 – 240
Heating engineer35 – 40150 – 450
Electrician50 – 80170 – 350
Plumber35 – 45200 – 400
Kitchen fitter20 – 50120 – 200
Wall plasterer30 – 50150 – 220
Decorator and painter20 – 50100 – 300

From table 7, you will notice that you need the services of several different professionals on your loft conversion project. Many of these peoples’ work lies in different stages of the conversion process. So they may not meet each other or be on-site at the same time.

However, that also means that you will have to manage their schedules to ensure that one person doesn’t delay another. If using a specialist loft conversion company, you may not have to worry about these. The company will manage the entire process and work schedule from the initial planning to completion and probably waste disposal too. 

What are the Additional Costs of Loft Conversion

Table 8: additional costs

ItemCost (£)
Heating50 – 4,800
Insulation500 – 800
Wet room3,000 – 7,000
Architect400 – 1,500
House renovation and painting800 – 4,000
Roof cleaning and repair100 – 600
Bat survey300 – 400
Building inspection400 – 800
Party wall agreement 150 – 1,000

Here are some additional costs that you might encounter.


Lofts are not the most insulated of places, so they lose heat faster than other areas of the house. Heating is usually simple because your property probably already has a heating system. All you have to do is find a way to integrate the loft into that system.

This also offers a great opportunity to check up on that heating system. If there is any issue, replacements go for £1,500 to £2,800 (for a boiler system), £1,500 to £3,500 ( for a combi boiler and £1,500 to £2,500 (for a heat-only boiler).

There is also the option to use heat radiators and underfloor heating. The former goes from £50 to £900 (regular radiator) and £90 to £400 (electric one). For the latter, there is wet underfloor heating at £60 to £150 per square metre and dry underfloor heating at £30 to £40 per square metre.



Apart from heating, you also need insulation to minimise heat loss. There are lots of options for these too. Sheet insulation costs £15 to £25 per m², loose-fill insulation (£5 to £15 per m²) and blanket insulation (£12 to £27 per m²). Whatever insulating system you choose, remember that you get what you pay for.


Wet room

If you want a bathroom in the loft, instead of building a partition with waterproof walls, you can simply install a wet room. It will save you and the loft conversion specialists a lot of stress. Wet rooms for around £3,000 to £7,000.

Whether using a wet room or building a normal bathroom, try to install it above the bathroom on the lower floor. This makes it easier to tap into the existing plumbing system for easy supply and drainage of water.

Architecture and design

You may not need this. You should probably talk to the loft conversion company first. Still, it is a great idea to hire an architect to help develop a design for your new loft. This will ensure that the accompanying modification won’t affect the structural integrity of the entire property.

Apart from making sure the engineering of what you are about to build is sound, the design also serves as a guide. It provides a blueprint for the loft conversion specialist to follow. As a result, the project could go much more smoothly.

Architecture and design

House renovation and painting

Since you will have several different tradespeople around, you can use this opportunity to have work done on other parts of the house. For example, you may decide to work on the roof, walls, driveway, etc.

House renovation and painting

Roof cleaning and repair

You will probably need to do some work on the roof, even if you don’t work on any other part of the property. For example, you may need to replace some damaged tiles, fix loose ones or clean the gutters. As a matter of fact, roof repair and cleaning should be one of the essential expenses of loft conversion. So expect it.

Expect to spend about£150 to £500 on pressure washing, another £150 to £500 to clean the gutters and £200 to replace damaged tiles. The latter depends on the type. For example, concrete roof tiles are cheaper than slate or clay roof tiles.

Roof cleaning and repair

Bat survey

If you have a pest problem in your loft, you will want to take care of that before starting the conversion project. But, if the pests are bats, things become a little more complicated than simply calling an exterminator. Bats are protected by the law, so you can’t exterminate them with a permit.

Before you can get a permit, you have to conduct a bat survey to determine the species. This could set you back by about £300 to £450.

Building inspection

Local authorities will need to inspect your project to ensure that it meets fire safety and building regulations. Their mission is mainly to ensure that the modifications made to convert the loft won’t affect the structural integrity of the building.

For these inspections, you submit your loft conversion plan (the one drawn by the architect) for review. Then, officials will also come on-site to inspect the project. It is up to you and your loft conversion specialist to ensure that the authorities conduct the review and final inspection. If not, you may run into legal troubles later.

The inspection alone could cost about £400 to £800. However, the official report may also include recommendations that will affect expenses.

Building inspection

Party wall agreement

For a semi-detached house, this kind of project may affect the party wall, which means it affects your neighbour(s). So you need a party wall agreement assuming responsibility for liabilities associated with the modification. For this, you will probably spend £150 to £200 on a party wall survey and £800 to £1000 for the party wall agreement.

What are the Factors That Affect Loft Conversion Costs?


Another look at Table 1 explains this perfectly. Size matters. In the table, I provided conversion prices for small-, medium- and large-sized lofts. As the material and labour need increase per square metre, so does the project’s total cost. So a small loft conversion will not cost the same as a big loft. It will be cheaper.

What you want to build the loft into

The sky is the limit as long as there is enough space. However, the more complex the structure, the more the project costs. Let’s use a study and a bedroom ensuite as examples. To make a study, a basic loft conversion will do. By basic, I mean, “just add some windows, flooring, stairs, and then paint.”

That is quite different from a bedroom ensuite which also needs internal walls, plumbing, a toilet and a bathroom. The internal walls alone can raise expenses by up to £700. The toilet will also need a macerator, while the bathroom needs padded walls and an extractor fan. At the end of the day, you might spend over £10,000 more than you would on a study.

The existing roof

There are two questions to ask about the roof. One, can it handle the extra weight you are about to add? Two, is there enough headroom? Whether your roofing system is rafters or trusses, you will still need to reinforce it with ceiling joists. If that won’t be enough, you may need a roof replacement. Either of these will affect your budget differently.

For the issue of headroom, building regulations require a distance of at least 2.2 metres between the ceiling and the floor. If the headroom in the existing roof space is not up to this, there are two options- raise the roof or lower the floor.

Option one is a lot more expensive, although it doesn’t matter if you already plan to have the entire roof structure replaced. However, roof replacement stirs up the need for building permissions which is an extra £170 to £200. On the other hand, lowering the floor is cheaper but it affects the headroom of the lower floor space.

Materials used

Table 3 to 6 explains this cost factor best. For example, velux windows are more expensive than dormer windows. The same goes for the different lighting, flooring and stairway options. Each type of material differs in durability and aesthetic appeal. They also differ in price. So the choice of material is a big cost factor.


Loft conversion costs in places like London will be higher by 15 to 20%. This increment may affect both supplies and labour.

Loft conversion type

This is the biggest cost factor, even bigger than size. The picture is clear and loud in Table 1. We will soon have a deeper discussion of the four types of loft conversion. However, there is something you should know before we do that. There is also another type (more like an option) called shell loft conversion.

It means having the loft conversion specialist build only the loft space, the shell, while handling the rest of the work yourself. Or have someone else handed it. As you may have suspected, this is significantly cheaper than the other options.

Types of Loft Conversion

Velux Roof light conversion

Aka “velux loft conversion” or “roof light loft conversion,” this is the “basic loft conversion.” To accomplish a roof light conversion, all you have to do is reinforce the ceiling and floors of the loft, add doors, windows and stairs and then decorate. That is all.

This is why roof light conversion costs are lower than the others. It is also why there is rarely a need for planning permissions since you won’t be making any significant modifications to the building. All of these make this type the most attractive option for a DIY loft conversion.

However, it is not all good. Velux loft conversions are only possible if you already have enough headroom. Remember? 2.2 metres between ceiling and floor. Once you have to remove or modify the roof structure, it is no longer a velux loft conversion. Plus, since the modification is minimal, it doesn’t add much extra space or aesthetic value to the loft space.

Velux Roof light conversion

Dormer loft conversion

With dormer loft conversions, there is a bigger modification of the roof. However, the modifications are still minor. For a dormer loft conversion, the existing roof has to have vertical walls. Then, loft extension, as well as windows, are built into those vertical walls.

As a result, the space increases. Ventilation and supply of natural light are also better. So, in matters of loft space and aesthetic appeal, dormer loft conversion trumps roof light loft conversion. It achieves this by making more significant moderation to the roof. Although not as much as the next two loft conversion types.

From the outside, a dormer conversion looks like a structure protruding from the existing roof slope. You will have noticed that a lot because this is the most common type of loft conversion in the country. Why not? It is cheap, suitable for all kinds of buildings and the resulting new loft space is spacious and beautiful.

Dormer loft conversion

Hip to gable loft conversion

This loft conversion type modifies the roof structure a lot more than the previous two. As a result, both space and aesthetic appeal improve. However, it also costs more money and requires planning permission.

To make a gable conversion, the slanted/sloped edges/sides of the roof are straightened. As a result, when you look at it from the outside, you have vertical gables on both sides instead of slopes.

Mansard loft conversion

This type of loft conversion costs the most, usually because it makes the biggest modification to the roof. In fact, it changes the roof entirely, raising it and the party wall to any desired height. After a mansard conversion, when looking from the outside, the loft has a flat roof and walls that slope inward at about 72 degrees.

A mansard loft conversion offers more headroom and loft space compared to the others. It also looks better. Due to the complexity and extent of the modification on the roof structure, mansard loft conversion requires planning permission and takes more time to build. However, it is worth it and suited for all sorts of properties, although it looks best on terraced houses.

Mansard loft conversion

How Do I Know if My Home is Suited for Loft Conversion?

Any building is suited for a loft conversion as long as you have the roof space. Roof space/loft space/attic space is the essential ingredient of loft conversion. However, some loft conversion types are best suited for specific types of buildings.

For example, a velux loft conversion is best suited when there is enough headroom. Likewise, a gable loft conversion is best suited for a roof with at least three slanted/sloped edges/sides. And mansard loft conversion looks best on a terraced property. On the other hand, any type of conversion looks good on bungalows. But note that bungalow loft conversion often costs more than other building types because they are usually bigger.

Still, the most important factors are budget, available loft space and what you want or like. You can have any house’s loft converted after settling those three. That is unless you are in a listed building. In that case, You can only make limited structural changes, such as in roof light loft conversion.

How do I Know if I Have Enough Headroom and Space for Loft Conversion?

The easiest way to know is to measure the loft space. All you need is a tape rule or any other measuring medium. Just measure the distance between the ceiling joist and the floor in the loft to see if you have enough headroom.

You can also check if there is enough room to put the permanent stairs. Although if there is limited room for that, you can resolve it by using a space-saving staircase.

Another option is to ask people who have done loft conversion on similar houses. One benefit of this approach is that you get to learn from their experiences and mistakes. You can also get their recommendation on loft conversion companies.

However, the only way to know for certain is to hire an architect to do an inspection. The same person can also help with the design. 

How do I plan for a loft conversion project?

Planning is crucial for this kind of project. There are so many moving parts that delays and disruptions can easily happen. Maybe due to poor management, unruly workers or even weather. These delays and disruptions can blow up your budget. Or worse, make the project take longer than it should.

That is why you need to plan. It doesn’t matter if you are doing DIY loft conversion or hiring a specialist or company to manage and execute the entire project from beginning to end. It still makes sense for you to understand the process. So, let’s talk about it.

However, note that these tips assume that you have already determined your house is suited for a loft conversion and have probably decided on a loft conversion type. We have said enough about those two. So, I don’t want to waste your time by going over them again. By the way, the following are not in any particular order.

Consider what kind of stairway you want and where to put it

There is only one rule when it comes to loft conversion stairs- you need to use permanent stairs. If you were already using the loft or attic before this (maybe as a storage space), there is a big chance that you are using a foldable ladder for it. However, that is no longer possible after having the loft converted. According to building regulations, you need a permanent stairway.

For help making a choice, you can go back to the section on supply costs to read up on loft conversion stairs costs and options. After settling on a choice, the next step is to choose a location to install the stairs. You don’t want it disrupting anything or anyone. You can also integrate it into an existing staircase if there is any.

Consider ventilation

You need windows for ventilation. So you or anyone in the loft can enjoy the fresh air and also curb mould. What type of windows do you want? How many windows should you and can you put in your newly converted loft?

Once again, we discussed some window options and their costs in the section on supply costs. However, I didn’t say much about the number of windows to use. That is because the answer depends on preferences and the size of the loft. You and your tradespeople can make that decision.

Finally, don’t rely on windows alone for ventilation. You can also add extractor fans, normal fans and air conditioners.

Consider insulation and heating

Both are crucial because a loft room tends to heat up and chill quickly. You need a heating system to provide heat and insulation to conserve energy. We have discussed options earlier, this time in the additional cost section.

Consider loft design and structural integrity

This is the part where you need an architect. Loft conversion doesn’t affect only the roof. It affects the entire building. So, you need a trained architect to make the calculations and decide the best ways to make those modifications without jeopardising the structural integrity of your house.

Plus, you will be getting a beautiful rendition of what the final loft space will look like after conversion. You and the loft conversion specialist can then use that design as a road map 

Consider documentation and legalities

This is the time to get the paper works in order. That includes building regulations approval, party wall agreement and planning permissions. However, that depends on whether you need them.

You will most likely need the building regulations. To get it, submit the loft conversion plans for approval and ensure that the building officer also comes to inspect the project after it is done.

About the party wall agreement, you only need this is your share a party wall with someone else. If that is the case, do the paperwork before construction starts.

About planning permission, you don’t need it for most loft conversions. Loft conversion is categorised as permitted development. However, in some situations, you will need planning permissions. I will tell you more about this in the FAQ section. But you can also get more information from your architect, loft conversion company or the official website.

How Long Does a Loft Conversion Take?

Table 9: how long does it take to convert lofts of 20, 30 and 40 square metres.

Loft conversion type20 square metre (weeks)30 square metre (weeks)40 square metre (weeks)
Velux roof light loft conversion  4 – 55 – 66 – 7
Dormer  loft conversion6 – 7 7 – 88 – 9
Hip to gable loft conversion6 – 77 – 88 – 9
Mansard loft conversion8 – 99 – 1010 – 11

This table shows that the main factors that will determine the duration of this project are the type of loft conversion and the size of the loft. This doesn’t mean that your project will follow the estimated time frame perfectly. Remember that delays, disruptions etc., can happen. That is why you have to pay close attention to planning and management.

What do I need to know about fire safety when converting my loft?

You have to think of loft conversion as adding another floor to your house. This new floor needs its own fire safety system. It also needs to be integrated into the fire safety system of the entire building. So, here are some things to consider.

  • Put a fire alarm system in the loft: Don’t rely on the alarms on the main floors.
  • Fireproof the loft: Fireproof both the floors and the ceiling.
  • Create a designated escape route: If the windows of the loft aren’t too high, they can serve this purpose. However, even a second-floor window is still high. So the best option is to put the loft’s stairs as close as possible to the main hallway or entrance.

How Do I Find A Good Loft Conversion Company?

Ask for recommendations. That is the easiest way. Ask friends and neighbours who have done similar projects. And if that doesn’t work, you can use other means like the internet.

However, when you find a company(s), you have to review them to determine if they are the right fit for the job. Here are some tips for that.

  • Ask about their previous similar projects (with videos and pictures as proof)
  • Ask if you could speak to their previous clients or see testimonials
  • Ask for written quotes with a complete breakdown
  • Ask if they belong to professional bodies
  • Ask for their licenses and insurance


Which is More Affordable, Loft Conversion or Traditional Extension?

Loft conversion is cheaper by around 50%.

It also takes less time to complete and requires less legal documentation. However, an extension offers more space  

What type of Loft Conversion is the most affordable?

Velux Roof light.

It costs about £ 20,000 to £36,000 for a loft of 20 to 40 square metres. For the others; Dormer loft conversion costs £25,000 to £57,000, Hip to gable loft conversion costs £30,000 to £80,000 and Mansard loft conversion costs £45,000 to £85,000

How Much Value can Loft Conversion add to My House?

A 15 to 20% increase in value.

This is based on facts collected by professional bodies.

How Much HeadRoom is needed for Loft Conversion?

You need at least 2.2 metres between the ceiling and the floor.

The ceiling being the ceiling joist and the floor being the bottom of the flooring material.

Do I Really Need an Architect?


You can do without hiring a professionally-designed plan but I recommend that you don’t for the sake of structural integrity and smooth execution of the project.

Do I Need to Tell Neighbours About the Work?

Yes, as long as you share a party wall.

In fact, you have to inform them not more than one year or less than one month before construction starts.  

Do I need planning permission?

It depends.

After everything that we have discussed, that is the most appropriate answer to this question. Remember, you need planning permission if loft conversion causes significant modification to the building’s structural integrity, like in cases of mansard and hip to gable loft conversions.

However, no matter the conversion type, you will need planning permission if-

  • Your house is a listed building
  • Your house is in a conservation area
  • The loft extension extends beyond the original walls
  • Via loft conversion, you raised the roof or added a balcony or veranda

The rules may vary slightly. That is why you need to check with local authorities.

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