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Loft Conversion Cost

In this article, we look at the cost of different types and sizes of loft conversions, as well as the prices based on the number of dormers. We’ll also delve into other relevant topics like how long such work should take, what converting a loft involves, and whether you can perform this job DIY.

3 - 7 weeks
Average price:
£20k - £30k

Introduction to Loft Conversion Cost

Want to know the price of a loft conversion? In this article, we look at the cost of different types and sizes of loft conversions, as well as the prices based on the number of dormers.

We’ll also delve into other relevant topics like how long such work should take, what converting a loft involves, and whether you can perform this job DIY.

If you’re considering paying for a loft conversion in the near future or down the line, the following guide will prove particularly useful.

A loft conversion involves turning a conventional attic space into one that is more useable and suitable to bedding or/and regular occupation.

This is a popular job as it allows homeowners to create a whole new room in their home without adding an extension or converting a pre-existing room. Read on to find out how much you’d pay for this type of work.

How Much Does It Cost to Convert a Loft?

For a loft conversion, the average cost of a bedroom with two velux windows is £13,000 to £20,000 with the price rising to about £18,000 to £25,000 for a bedroom with an ensuite and two velux windows, £20,000 to £25,000 for a bedroom with a dormer and single velux window, or £25,000 to £30,000 should you want a bedroom with an ensuite, one dormer, and one velux window.

For a loft conversion that has a bedroom with two roof light windows, you’d need a budget of around £20,000 to £22,000 should it be 4m x 5m, £26,000 to £28,000 if its 5m x 6m, or £40,000 to £42,000 for a 12m x 8m conversion.

For a bedroom loft conversion with four roof light windows, expect a total bill of £22,000 to £24,000 for a 4m x 5m conversion, £28,000 to £30,000 for a 5m x 6m conversion, or £42,000 to £44,000 in the case of a 12m x 8m conversion.

As for a loft conversion with a bedroom that has a single dormer and one roof light, the overall cost lands around £30,000 to £32,000 for a 4m x 5m conversion, £40,000 to £42,000 for a 6m x 5m conversion, or £58,000 to £60,000 for a 12m x 8m conversion.

Lastly, a loft conversion bedroom with two dormers and two roof lights is priced at roughly £44,000 to £46,000 for a 5m x 6m conversion, or £63,000 to £65,000 if it’s a 12m x 8m conversion you’re after.

Labour Cost

As for the labour cost, with around 2-4 tradespeople working on a loft conversion simultaneously, each specialist charges roughly £300 to £500 a day. As a result, the total daily labour price would likely end up between £900 and £1500 per day.

Cost Factors

Here’s the factors that determine the cost of converting a loft:

  • Type of Dormer
  • Size of Dormer
  • Number of Dormers
  • Ease of Access
  • State of the Loft
  • Property Location

The price of a loft conversion will vary depending not only on the type, size, and the number of dormers but also ease of access, the state of the loft, and property location.

Where you live is a cost factor due to labour costs differing throughout the UK. For instance, labour prices tend to be highest in the southeast (London especially) but below the national average in regions such as Scotland, Northern Ireland, and northern England.

Loft Conversion Prices:

Job Description Size in Metres Total Cost
Bedroom with 2 Velux Windows 4 x 5 £13,000 to £20,000
Bedroom with Ensuite & 2 Velux Windows 4 x 5 £18,000 to £25,000
Bedroom with 1 Dormer & 1 Velux Window 4 x 5 £20,000 to £25,000
Bedroom with Ensuite & 1 Dormer & 1 Velux Window 4 x 5 £25,000 to £30,000
Bedroom with 2 Roof Light Windows 4 x 5 £20,000 to £22,000
5 x 6 £26,000 to £28,000
12 x 8 £40,000 to £42,000
Bedroom with 4 Roof Light Windows 4 x 5 £22,000 to £24,000
5 x 6 £28,000 to £30,000
12 x 8 £42,000 to £44,000
Bedroom with 1 Dormer & 1 Roof Light 4 x 5 £30,000 to £32,000
6 x 5 £40,000 to £42,000
12 x 8 £58,000 to £60,000
Bedroom with 2 Dormers & 2 Roof Lights 5 x 6 £44,000 to £46,000
12 x 8 £63,000 to £65,000

Types of Loft Conversion

A loft conversion may come in various forms. This section will look at the features, quality, cost, and pros & cons of some examples.


The least expensive option is a Velux loft conversion. This type of conversion is also the least difficult and involves minimal disruption, although it offers less space than other choices.

Velux loft conversions do not involve roof alterations since windows are simply fitted into the current roofline. Once the floor is installed, a staircase is added, where sufficient space is available in the loft. On average, these loft conversions cost around £15,000 to £20,000.


✔ Relatively inexpensive

✔ Least difficult conversion

✔ Less disruption

✔ Not as much space needed


✖ Won’t be as large as other conversions


A dormer loft conversion or extension involves adding to the amount of headroom in the loft. This involves creating a new space that protrudes out from the attic’s roofline.

It is most the popular type of loft conversion. Dormer conversions are suited to most properties, although they are relatively costly with an average price range of £35,000 to £55,000.


✔ Add headspace

✔ Well-suited to most homes


✖ Dormer loft conversion cost tends to be relatively high


Generally, a hip-to-gable conversion is the most expensive, as it involves altering the shape of your home’s roof.

The extension involves adding to the top life of the property’s roof in such a way that it will be made to run right to the edge of the home. This results in a vertical gable along the side of the property. This may be constructed with tile or brick.

The purpose of a hip-to-gable conversion is to significantly expand the room in the loft for the conversion. However, this can only be achieved with a detached or semi-detached property that has a sloping roof.

In the case of a detached property, you may have both sides converted in order to establish a double hip-to-gable loft conversion. On average, a hip-to-gable loft conversion costs between £40,000 and £70,000.


✔ Creates a lot of space

✔ Double conversion possible with a detached house


✖ Often particularly costly

What Does Converting a Loft Involve?

Let’s now break down the steps of converting a loft. Please note that each type of conversion will have slightly different requirements to build.

1. Planning and Hiring Contractors

Firstly, you’ll want to think through carefully what sort of loft conversion you’d like. You may wish to hire a professional architect or/and structural engineer to help you with your design. They can also assist in ensuring that your plans will meet the building regulations.

Once your plans are in place, it’s time to hire the right contractors/company for the job. To improve your odds of hiring an above-average contractor, you should acquire three distinct quotes and ask for references too.

2. Key Construction

On the day of construction, the labourers will arrive and set up scaffolding around the loft area externally. A roofer will take down the sections of tiles needed to allow the construction of the new dormer structure (if applicable).

Steel supports then may be added so that the frame across the loft and over the ridge of your home’s roof.

As soon as the internal structure has been installed, the joists may be put into place, as well as the boards that are needed for the base of the new roof.

Next, the front boarding should be added with the positioning of doors and windows kept in mind. It is then time to install a water-resistant membrane.

This will protect your loft conversion from rainfall. The last part of this step will involve any further roof structure alterations. Such changes may include raising the roof, strengthening a trussed roof, or rafter strengthening.

3. Add Insulation

We will now move to the addition of the loft’s insulation. There are two primary ways of insulating a roof; adding a 70mm slab foam between the roof’s rafters per the cold roof method or protecting with 100mm of Celotex insulation installed over the rafters.

In the case of a semi-detached or attached property, insulating the party walls may be needed to prevent heat loss or absorb sound.

4. Install Electrics & Lighting

Among the electrical installations required are temporary first fix electrics, the installation of carcass wiring, earth road, and backboxes, as well as potentially cross bonding and earthing the pipework. Next, the loft’s wiring will be fitted into the walls.

But that’s not all…

Each cable needs a tolerance of 150mm. Then, the walls must be plastered before new wiring can be installed for the lighting, power sockets, security systems, and the consumer unit.

Tests must be undertaken to make certain that the electrics are safe and secure. With the electrics fitted, lighting may be added based on your preferences.

5. Fit the Windows, Doors, and Staircase

Of course, you may wish to have a dormer window inserted, among other window types. In accordance with the fire safety regulations, it is necessary to have a fire door installed either at the bottom or top of the staircase.

The door needs a fire resistance time of 20 minutes, and it cannot be glazed. A professional must perform this installation.

Next, suitable loft conversion stairs should be added. The staircase will likely have around 13 steps and cannot have any more than 16. Corner steps are likely to prove necessary. Once this is installed, a plumber may not fit the pipework.

6. Add the Plumbing

A plumber must install any necessary pipework. You may wish to have a bathroom fitted to your conversion too. The existing pipework must be connected to the loft either way.

If the pipes are installed at roof level, this work will prove significantly easier than if the pipes are installed on the next floor down.

Wall-mounted fittings are a great way of making the most of the space, particularly if you have a relatively small loft conversion.

7. Install the Heating

As soon as the pipework has been added, you may require a boiler update, particularly if a loft bathroom has been added.

A qualified professional is needed to perform this work. The new boiler will likely be installed in the same location as the current boiler. Then radiators or underfloor heating may be installed, depending on your preferences.

8. New Floor

Of course, the flooring area must be considered throughout the loft conversion before the new flooring can be fitted. An underlay should be added before the actual is installed.

The purpose of an underlay is to act as insulation for heat and sound. Lastly, trim and mouldings should be added to the floor’s edges.

9. Plastering & Painting

The final phases of creating a new loft space/conversion involve adding plasterboards on each wall before the walls may be primed and then painted.

You may paint or/and decorate the wall DIY if you wish. Give it enough time after plastering to paint and sufficient time between each layer of paint too. Installing wallpaper, on the other hand, may take more time.

DIY Loft Conversion

Most of the work involved in converting a loft is not considered a job for the average DIY enthusiast. Builders will likely be needed to build the walls and insulate the loft.

Of course, an electrician must add electrics and any pipework dealt with by a plumber or heating engineer.

It is best to hire professional(s) to install flooring, windows, doors, and the staircase. However, plastering, painting, and any necessary decorations are more suited to DIY work.

There are planning permission and building regulation rules to consider, which are laid out on the Planning Portal.

Please note that the Planning Portal applies specifically to England and Wales, and therefore, rules may differ in Scotland and Northern Ireland.

Building regulations approval is needed to convert a loft space, and planning permission approval may be required.

Rules may also apply separately to additional work such as electrics and heating. A professional may sign off the work when completed, such as for building control.

Among the risks of converting a loft by yourself are the dangers of working at a height and working with heavy objects/hazardous tools. On a less serious note, there is always a risk of incorrectly constructing the loft conversion.

This would result in the need to pay for professionals to come by and fix the work anyway, beyond any work that legally must be performed by professionals.

Potential Problems and Pitfalls

As with any work, there are some broad downsides worth considering. For one, it is time-consuming and disruptive. In fact, most loft conversions take around one to two months altogether.

If your application for building regulations or/and planning permission happens to be rejected, you’ll need to re-submit your application(s) with the required changes.

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Sam J

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