L-shaped terraced loft conversions – what are they?

By Jon Pritchard In Loft bathroom/ensuite, Loft conversion, Loft lifestyle 3 Comments

What is an L-shaped loft conversion?

L-shaped loft conversions extend over the rear extension that exists in many Victorian and Edwardian

are ideal for Victorian and Edwardian terraced properties where there is a back addition at the rear – usually housing the kitchen in the ground floor and a bathroom above.  It means that you have a little bit more area to build over, and can achieve a larger loft conversion.

Aerial illustration of a full bathroom added as part of an L-shaped loft conversion.

This L-shaped loft conversion enabled our customer to add a full bathroom, with separate shower and  freestanding bath.

If you have a rear addition to your terraced home, you can consider an L-shaped loft conversion. The benefits are:

  • The maximum cubic meters allowable under UK Permitted Development rules (meaning you probably won’t need planning permission) is 40 cubic metres for a terraced home*.
  • Most terraced homes are not able to completely maximise this allowable space with a standard flat-roofed dormer loft conversion.
  • By extending your dormer over the rear extension, you end up with more extra space once the conversion is completed.
  • Practically this adds about the size of a 2 metre by 2 metre room compared to a standard terraced loft conversion.  This can be incorporated into your loft conversion design to include a small study, to fit in a bathroom, a good walk-in-wardrobe or, as one of our customers had, a champagne fridge!  Don’t hold back with your imagination or your dreams!
Computer illustration of a terraced flat roofed loft conversion including double doors and a glass juliet balcony

Standard terraced flat roof loft conversion – the dormer goes party-wall-to-party wall only.

Different designs for an L-shaped loft conversion

In order to keep any loft conversion within Permitted Development regulations, your design must not add more than forty cubic metres to your home. There are various ways to design your L-shaped loft conversion to make the most of this allowable space.

The standard design for this type of terraced loft conversion includes a flat roof dormer across the rear of the main roof, extending round and over part of the rear addition. This would not normally extend all the way to the back of the rear addition, simply due to the need to keep the design within the allowed forty cubic metres.

3D image showing a terraced home loft conversion from the rear exterior. The terraced home has a rear extension and the loft has been extended with a flat-roofed dormer across the width of the main roof, and then a further addition above a small part of the rear extension.

The flat roofed dormer extends across the width of the house, with an addition over the rear extension housing, in this case, an ensuite.

If you want to extend the roof of the entire rear addition, the main roof dormer would necessarily be smaller, extending only part way across the roof.

A large Velux window can then be added to allow light into the remaining portion of the main roof.

Illustration of the rear of a Victorian terraced home with a rear extension. The illustration shows how the loft can be converted to add a floor to the home, extending over the rear add-on with a flat-roofed dormer, and installing a large Velux window alongside in the remaining rear original roof.

An ‘L-shaped’ loft conversion on the rear of a terraced home with the main part of the dormer over the rear extension. This design includes a Velux Cabrio Roof Window/Balcony

What can I fit into my L-shaped dormer loft conversion?

The answer is – whatever you like! With some terraced loft conversions it can be tricky to fit in an ensuite. However, with an L-shaped conversion this becomes much easier and, as the image at the top of this article shows, you may even find you can fit a full bathroom.

A popular design choice is to add double doors and a juliet balcony to the flat roof dormer over the main rear roof at the rear of the property, with velux windows adding light at the front.

Computer designed illustration of the master bedroom created by extending a terraced home with an l-shaped loft conversion

The master bedroom in this L-shaped conversion enjoys the full available width of the loft conversion, with Velux windows to the front and a large window in the dormer at rear. It includes a built-in wardrobe, cupboard and storage in the eaves.

Could I get planning permission for a larger L-shaped loft conversion?

In our experience, most councils do not approve planning permission for larger L-shaped dormer loft conversions. Contacting us to discuss your ideas and your needs. Our experienced designer can help you to create a loft that will increase the value of your home, maximise the available space and move your lifestyle up!

Example floorplan for an L-shaped loft conversion including double bedroom, ensuite and storage.

Example floorplan for an L-shaped loft conversion including double bedroom, ensuite in the dormer, walk-in wardrobe and further storage cupboards.


*Note that for detached and semi-detached homes, the volume allowance is 50 cubic metres additional roof space.

**Any previous roof space additions must be included, whether part of your current loft extension plans, or already existing.

Visit our gallery to see images of our terraced propertes with L-shaped loft conversions, – with full bathrooms.

You may also find our article on this Bristol Terraced Loft Conversion helpful, as well as this one about making your loft conversion bathroom a wetroom – fantastic for smaller spaces.