The Homeowner’s Guide to Dormer Loft Conversions

dormer loft conversion construction

A dormer loft conversion can completely transform a dark, unused loft into an integral part of your home, adding value to your property and acting as an extra bedroom, office or play space for the kids.

The dormer is an extension shaped like a box, which overcomes the classic problem of lack of headroom! You can flood your attic with natural light, adding a spacious window, and maximise your living space.

Different Types of Dormer Loft Conversion

No two properties are identical, and you can customise your dormer loft conversion design, to select the right finish, style and layout to match your property, improve curb appeal or meet your aesthetic aspirations.

One of the key pieces of advice is to ensure the dormer is proportionate, so it doesn’t extend outwards too far or look out of place.

Examples of dormer loft conversions are as below.

Gable-fronted or Doghouse Dormer Conversions

This type of dormer roof is pitched, with slopes on either side, called a doghouse because it replicates the appearance of a traditional outdoor kennel.

You can build a small gable to boost the light or opt for a larger gable if you have a bigger property and need as much space in your new room as possible.

Flat Roof Dormer Loft Extensions

Flat roof dormers are just as they sound. The space is functional because there are no sloping walls that eat into the overhead capacity, but some property owners prefer a pitch on their dormer as a square roof can clash with the existing roofline.

Mansard Dormer Attic Conversions

Mansard lofts are typically constructed to the rear of a house and have a flat roof but with angled walls running down on either side.

The Mansard dormer is built along the whole roof, making almost an entire additional storey, so while this type of loft conversion is one of the more expensive options, it also provides the most space.

Hip Roof Dormer Extensions

Roofs are almost always sloped (or hipped), which creates the normal angle restricting the height of your converted attic. If you choose a full hip roof conversion, your contractor lifts the side hip to make it higher or even vertical.

Adding a hip roof dormer involves adding an extension to the roof, so you end up with three sloping sides that extend the space upwards and horizontally.

Shed Dormer Lofts

Shed dormers have a slope that replicates the angle of your main roof, but at a lower angle, and is a cost-effective option since there isn’t a peak or hip. A shed dormer can be extensive and add considerable space to your loft.

L-Shaped Attic Dormer Conversions

An L-shaped dormer is actually two dormer extensions. One is positioned over the roof, and the other to the rear of the property, meeting in the middle to create an L shape.

This dormer conversion is popular for terraced Victorian properties with steep roof angles.

What Are the Pros and Cons of Investing in a Dormer Loft Conversion?

The primary advantage of a dormer loft conversion is that you can add a sizable volume of head clearance and floor space to your property. Your attic has limited use, even with a Velux window, if the roof pitch remains steep, making it impossible to stand other than in the middle of the loft.

Depending on the size of the dormer, you can even create two extra bedrooms, or a bedroom suite with a seating area, as a whole new storey.

Other Advantages of a Dormer Attic Extension

  • Increasing the light in your attic, with multiple opportunities to install thermally efficient glazing to capture natural sunlight.
  • Panoramic views, particularly for properties in cities. A rear dormer can incorporate a balcony or large picture window to make the most of the local scenery.
  • A dormer is a great way to improve the appearance of your home, making it more attractive, and boosting the saleable value if you choose to put your home on the market.
  • Dormer conversions improve the airflow in your home, introducing more fresh air and preventing rooms from becoming stuffy.
  • Enhances safety – you can use a dormer as an emergency exit in the event of a fire, making your home safer for everybody sleeping upstairs.

There are multiple designs and options, so a dormer loft conversion is versatile and tailored to your property and requirements.

Drawbacks to Installing a Dormer Loft Extension

It is important you know all the positives and pitfalls before you embark on any large home conversion project and make informed decisions about the best solutions for your property and family!

Dormer conversions involve removing a section of the roof to add a new extension to the structure. Hence, the work is inevitably more involved and takes longer than simply adding a new window flush with your existing roof.

You will need a professional building contractor or structural engineer to help with the design process and ensure the added dormer is sound and installed correctly.

A dormer loft conversion is more likely to need planning permission, although you can often build a rear dormer as a permitted development.

Is My Property Suitable for a Dormer Loft Conversion?

Not every home is suitable for a dormer attic conversion, depending on:

  • The pitch of the room.
  • The amount of head clearance.
  • The structure of the property.
  • Accessibility challenges.

Chimneys or water tanks fitted into the roof can make it more complex to add a dormer extension, but a qualified roofer can advise whether they can remove or work around these features.

Building regulations dictate that the minimum clearance room is 2.2 metres, so you need to check whether the room’s height will comply – a roof with a very low pitch might not be eligible if the dormer won’t reach this threshold size.

There are solutions if you don’t have sufficient height to meet building regulations. Still, the conversion work can become more expensive since you would need to either lower the ceiling height of the storey below or raise the existing roofline.

You also need to check whether you have rafters or roof trusses holding up the roof. Rafters are found in most homes built since the 1960s and don’t eat into the floor space.

Trusses are frames shaped like a W and take up additional space, so your contractor would need to fit structural supports before they would be able to remove the trusses.

Planning Permission Rules for Dormer Loft Conversions

Most rear dormers are eligible for permitted development status if the front of the property doesn’t change.

If you want to build a dormer at the front of the house, you will usually need formal approval because this will impact the privacy of public roadway users and the property’s outward appearance.

There are also limitations on the size of dormer extension you can build as a permitted development. Terraced homes can have a dormer of up to 40 cubic metres and up to 50 cubic metres for a detached or semi-detached house, but anything larger must have full planning permission.

Note that permitted development rules apply only to houses (excluding flats) and are not available in conservation areas or for listed buildings.

Building Regulations for Dormer Attic Extensions

Building regulations cover all construction work, whether or not planning permission is required. The laws cover a range of factors and ensure that work is structurally safe and complies with rules around things like fire safety.

For example, a building inspector will check the weight-bearing capacity of the floor, fire exits, and the stairs leading into the loft.

Some accredited contractors can self-certify that their work meets the regulations and, in other cases, can help organise for an inspector to visit your property and provide compliance confirmation.

Party Wall Considerations for a Loft Dormer Conversion

The Party Wall Act 1996 applies when your house is terraced or semi-detached, and you want to make changes to your home that affect the shared wall between yourself and your neighbours.

You might be able to come to an agreement with your neighbour and proceed without delay if they are happy to consent to the work.

In other cases, you will need to hire a party wall surveyor to ensure you have a formal arrangement and the correct authorisation to proceed with your loft conversion.

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