Adding a new dormer window can really improve the look and feel of your home, as well as increase the headroom and maximise the usable floor area. A dormer can also turn a cramped attic into a full-height room with plenty of natural light. So are you planning to convert or refurbish your loft space? Find out how much a dormer window costs with our price guide and advice.

How much does a Dormer Windows cost?

Average cost in UK: £925

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The average cost for a Dormer Windows Units is £925. You are likely to spend between £600 and £1250 total. Exact price may vary depending on your area and project details.

Next Step: Find out exactly how much your project will cost.

How much does a Dormer Windows cost?

Average cost in UK: £925

Get local prices






The average cost for a Dormer Windows Units is £925. You are likely to spend between £600 and £1250 total. Exact price may vary depending on your area and project details.

Dormer windows are best suited for converted attic or loft rooms. Designed to act as a neater, more structurally sound ‘skylight’ that looks out onto the street below; dormer windows simultaneously offer improved lighting and ventilation while also creating extra head space by jutting out of the main property.

How much does it cost to add a dormer window?

Revitalizing your dormer loft conversion or attic conversion? Adding a dormer window can do wonders- brighten up a cramped and dark space while also making it appear larger. Installing a dormer window typically costs between £650 and £1,250 per window. The price tag varies based on the size and type of dormer window as well as the material used.

Dormer Window Costs Summary

Price Range = £600 to £1,250 (for the window and installation)

Average Cost = £925

Cheapest Price = around £600

Most window installers will automatically offer quotes based on double-glazed (rather than single-glazed) windows; but if their terms are unclear and you remain uncertain, don’t be afraid to ask! Obviously, the cost of a double-glazed dormer will vary across the country, but for a typical dormer installation you should aim to budget for the following prices:

  • Materials – £300 to £600 (this usually includes both the frame and outer casement of the entire unit, along with the glass pane itself)
  • Scaffolding – anywhere between £200 and £350 (and, unlike ground-floor window installation, completely necessary according to building regulations)
  • Labour – Dormer window installation can usually be completed in a single day, but obviously, the time the job takes will depend on how many windows you want to be fitted and/or how large the window space is. Most contractors charge around £100 to £150 per day for labour costs, so the final price shouldn’t be anything over £300.

The prices listed above are typically for a flat roof dormer window, if you would prefer a sloping or ‘ simple pitched’ roof to add dimension and style to your attic renovation, then you should also add an additional £700 to £900 to the final cost.

What is a dormer window?

A dormer is a roof structure that projects vertically from a pitched roof. A dormer structure is a type of dormer that contains one or more windows. A dormer window is essentially a vertical extension of a horizontal roof, and they are often used to add extra light and space into an attic or other room with a sloped ceiling. While they can be added for purely aesthetic reasons, many people also find that dormers help improve the energy efficiency of their homes by adding insulation and preventing heat loss through the existing roof.

cost of dormer windows

Why are homeowners adding dormers?

Dormers are commonly seen as an upgrade, especially for those who want to replace existing skylights in a loft conversion or attic conversion. Dormer windows are popular because they let in more light and make the space inside the loft bigger, something a Velux window or roof light can’t do. Dormer windows not only provide views of the outdoors, but they also give a better sense of depth and perspective than regular skylights. Plus, installation is often possible without having to incur full re-roofing costs.

Dormer windows can be a stylish addition to your home and existing roof shape, and can even become a real feature along the roofline. Adding a dormer window will let in additional sunlight and make the room feel bigger by increasing headroom. This extra space can make small rooms feel less cramped and give you more interior design options.

What are the cost factors when adding a dormer window?

The dormer window costs will be divided between the labor and materials. To ensure a snug and watertight fit, there is a fair amount of work that has to be done to adapt the roof accordingly, which includes making sure the integrity of the roof is not compromised around where the windows will go.

If you plan to make any changes to your roof, no matter how small, you must have an architect or engineer create drawings and plans. You will also need their help if you want to apply for planning permission. The cost of installing dormer windows will be calculated by taking all of these elements into account.

Additional Costs of Installing an Attic Dormer Window

Along with the window, frame, construction work and labour hours, several other pricing elements will likely feature on your quote:

The cost to move an attic water tank is £300-£800.

The average cost of roof truss replacement is £12-40 per metre square.

Professional roofers typically charge around £11,000 – £15,000 for roof modifications.

The cost of appropriate ventilation mechanisms typically falls between £250 and £400, depending on the size of the property.

Attic underfloor heating usually costs between £20 and £30 per square metre.

The price of scaffolding for your window fitter depends on the expected duration of the job and if you have existing scaffolding from other detailed projects, like a loft conversion.

Types of dormer window

The dormer window design you choose should be based on complimenting your current roof design. Different dormer windows are named after their roof type. Some of the most common options are listed below:

The Flat roof dormer window is popular among people because it creates more internal space and is economically friendly.

The Shed Dormer has a single-planed roof that slopes down at a shallower angle than the pitch of the main roof.

Gable dormer window – This is a gable fronted dormer design with a pitched roof, sometimes referred to as a doghouse dormer because it resembles a kennel. This style is popular for large, older homes and cottages as the traditional look is more in line with the age of the building.

Hipped dormer – this type of dormer roof windows has three sloping planes and would often be installed with a fully-sized hipped roof that mirrors the styling.

Eyebrow dormer window – The Eyebrow dormer window, sometimes called eyelid dormer, is a roof extension with no sides. The top element of the roof curves upwards, usually in a brow shape over and above a low, wide window. This style dates back to ancient times and is often used for homes that have traditional thatched roofs.

Blind or false dormer – This design feature only has an external impact and provides no extra light or space internally.

Will I need planning permission to add a dormer window?

Many loft conversions and/or dormer window additions are allowed under the UK’s ‘permitted development’ rules and don’t need planning permission. However, there are some restrictions and limitations placed on permitted development. For example, you would need to apply for planning permission if:

– Your home is located on protected land, like an area of outstanding natural beauty, national park, or world heritage site.

– The volume of the converted space exceeds the permitted limits (currently 40m3 for terraced houses, and 50m3 for detached and semi-detached houses).

– The dormer extension will be built at the front of the house (facing the street) and extend higher than the existing roof.

The dormer conversion features a balcony or veranda, or side-facing windows that offer views of neighboring properties.

Even though you might not need planning consent, loft conversions generally entail some form of structural work, so you will need building regulations approval. After your renovation specialist explains what’s involved in your project, they will then be able to go over how your design choices might affect the application processes and building costs. This way, you will have a better understanding of the entire process and know exactly what you’re getting into before making any final decisions.

Get quotes for new dormer windows

Please let us know how many windows you need and what type. We are connected to a national network of window installers from all around the United Kingdom. We’ll connect you with local dormer window fitters – compare different quotes and save money on your new windows.