Your guide to a dormer loft conversion

Loft conversions are one of the simplest ways of extending your home, without using space from the garden...ideal in built up areas where the only option is to go upwards. Today, we look specifically at Dormer loft conversions, from how much one will cost, to planning permission requirements.


Dormer loft conversion by Architect Your Home

What is a Dormer loft conversion?

A Dormer loft conversion is one of the most common types of conversion in the UK and is ideal for a semi-detached or terraced home in a built-up area. In a Dormer conversion, the roof is extended vertically to create more headspace and more usable floor space. Unlike a Velux conversion, a Dormer loft conversion will require structural changes to your roof. 

Flat roof Dormer loft conversions are very popular and can give maximum floor space. They are a fairly straightforward loft conversion as they protrude straight from the roof. 

Pitched roof Dormer loft conversions are less popular as they give less floor space in the loft, as there is no vertical roof. However, they tend to look more attractive than flat roof dormers from the outside, so can be popular at the front of a property or on an older property where you want to add to the character.


How much does a Dormer loft conversion cost?

A Dormer loft conversion cost can vary depending on:


  • where you live in the country
  • complexity of your Dormer loft conversion
  • whether you are fitting a bathroom or not
  • the quality of product finish and the size. 

For example, in London a 20 square metre Dormer loft conversion with 1 bathroom and finished to a medium end specification will cost around £50,000 - £55,000 (this would include VAT and all of the finishes). A similar loft conversion in the North of England could cost around £35,000 - £40,000.

Our cost estimate will give you a rough guide of your loft conversion cost based on where you live in the UK and size, so it's a great place to start.


How long will a Dormer loft conversion take to complete?

Assuming all goes to plan and your loft conversion is standard, a new Dormer loft conversion would take around 4-6 weeks for the structure and allow another 2-4 weeks for the finishing and decor. 


Do I need Dormer loft conversion planning permission?

The best thing about loft conversions in general is that they can normally be done within permitted development, which means they don't need planning permission.

Dormer loft conversions are most common to the rear or sometimes to the side of the property, in which case you are more likely to be within permitted development, as long as your property meets the other requirements, such as being within a conservation area. 

Dormer conversions to the front of your home will almost certainly require planning permission as they are overlooking the main road.

Other factors which impact whether your Dormer loft conversion is within permitted development would include the size of the loft conversion, the type of property (a maisonette for example would always need planning permission), whether you live in a conservation or another notable property, and the style of your Dormer loft conversion.

To find out more about loft conversion permitted development, then check out our advice on when is a loft conversion permitted development.

Always check with your local authority on whether your property will require planning permission. 

What other things do I need to look out for?

If your home is a terraced or semi-detached property and live in England and Wales, then it is likely that you will need a Party Wall Agreement from your neighbour(s). This is because your work will be cutting into the party wall for structural beams and raising the party wall to construct the dormer. To find out more about the Party Wall Agreement, check out our expert advice article.

You will also need to make sure that your work complies with building regulations and you get approval for the work you are carrying out. Read our guide to find out more about building regulations approvals.

Published: August 28, 2019

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