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Why Have a Dormer Extension?

If you are considering a loft conversion, then you may be wondering why have a dormer extension? After all, there are other types of loft conversion such as hip to gable, Velux and mansard types to choose from.

If you are unaware what a dormer extension is, then it is simply a type of loft conversion.  The best way to imagine this is a structure in the shape of a box coming out the side of your roof.  This method expands the usable space within your loft space, so you can squeeze more rooms into it.

Dormer extensions are probably the most common type of loft conversion.  This is because they often add the maximum amount of additional space for your money.  Dormers are not always simply a box with a flat roof, as sometimes they are modified to look more attractive by installing a low pitched roof on them.  However, doing so would reduce the space and cost more to build.

Requirements for Dormer Extensions

Does a Dormer Extension need Planning Permission?

Planning permission is only required when extending or altering the roof space, and if it exceeds specified limits and conditions.  Your architect or builder can help you decide what is required.

Does a Dormer Extension need Building Regulation Approval?

Yes, all loft conversions require building regulation approval.  This also applies even you do not require planning permission.  When you start your extension a Building control surveyor will inspect your work at various stages.  Once approved they will issue you with a certificate on final inspection.

How many Additional Rooms Can I have?

  • The shape of your roof can influence how many potential rooms you can have.  If you have an awkward shaped roof it may be difficult to add an extra room without it looking strange.  Ideally you want your loft conversion to look as natural as possible.
  • Usable space that a loft conversion can provide is based on a head height of at least 2.2m.  This is the distance between the bottom of the ridge timber to the top of the ceiling joist.
  • What is your current roof pitch angle? Higher pitched roofs enable more additional loft conversion space.

Loft Conversion Process

  1. First hire an architect.  They can tell you what your options are regarding rooms and space.  They can design the loft conversion using CAD, and calculate the necessary supporting steel beams you need.  An architect will provide drawings of your loft conversion design.  The builder you hire will refer to these drawings throughout the project.   
  2. Your architect will draw up your detailed loft extension plans for you to see.  Once you agree on the ideal plans, they can then be sent to planning permission (if necessary).  If planning permission is not needed, they can then be sent directly to building control.
  3. Once building control approve your drawings, you are then ready to build.  However, building control will carry out site visits throughout the project to ensure it is being made to the drawings.  And that all current building regulations are met.  Building regulation surveyors have the power to decline or approve a certification for your new loft extension. 

Types of Dormer Loft Extension

Flat Roof Dormer

This is the most popular type of dormer extension in the UK.  The extension is boxed shaped with a simple flat roof.  This is also the cheapest type of dormer to install.  It also offers the largest amount of usable space.

Shed Dormer

Often used in homes with a gable roof, shed dormers have a flat single planed roof.  They are sloped downwards at an angle.  Shallower than the main roof.  The downside is that they usually require different roof sheeting to that of the main roof.

Gable Fronted Dormer

Also known as a “dog-house dormer”, they are a more attractive option when it comes to loft extensions.  They consist of a gable wall extension which is built up to the existing ridge line.  Then a new roof section is built outwards to the new gable end.

Hipped Roof Dormer

These are similar to a gable fronted dormer, but has three sloping planes of a hipped roof converging at the ridge of the dormer.  They are the most attractive option, but can reduce the amount of extra space compared to flat roof dormers.

Rough Cost of a Dormer Loft Extension

One of the hardest questions to answer when considering a loft conversion is how much one actually costs.  This is because there are so many different aspects of a project that can influence the price.  Every house is different, and so is each customers requirements.  However, we did write an article on typical loft conversion prices in the UK, as a rough guide only.


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Posted on 11th October 2017 at 10:18 am

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