L Shaped Loft Conversion
L Shaped Loft Conversion
An L shaped loft conversion joins two separate roof extensions together to form one larger space, shaped like the letter L when you look at the floor plan from above. Most houses that suit this style already have a rear addition, sometimes called a closet wing or a return, sitting behind the main part of the house. One dormer is built over the main roof and a second, smaller dormer is built over that rear addition. The two are then linked internally.
This approach gives you a lot more usable floor space than a single dormer on its own. It is a common choice when a family wants two new rooms out of the loft, for example a bedroom and an ensuite bathroom, or two separate bedrooms, rather than just one larger room.
Because it involves two structures instead of one, the build takes a little longer and the roof work is more involved. It also depends on the house already having that rear addition in the first place, so it is not an option for every property. A survey of the roof and the rear addition will tell you quickly whether your home is suited to this style.
Who this for
Victorian and Edwardian terraced houses with a rear addition or return are the classic candidates for an L shaped conversion, since the second dormer sits naturally over that existing lower roof. Some semi detached houses of a similar age and layout can also suit this style, provided they have the same rear addition feature.
Project Process Steps
We survey both the main roof and the rear addition roof separately, since they are usually different heights and different structures, and we need to understand how they will connect.
Our structural engineer works out how the two new dormer structures will tie into the existing walls and into each other, since this is a more complex structural job than a single dormer.
We build the main rear dormer first, then the smaller dormer over the rear addition, then join the two internally so they read as one continuous space rather than two separate rooms.
Once both structures are weathertight, the interior work, plumbing, electrics and finishing follow the same stages as any other loft conversion.
Frequently asked questions (FAQ)
Does an L shaped loft conversion need planning permission?
This depends on the size of the finished result. L shaped conversions are often covered by permitted development provided the whole project, including both the rear dormer and the extension over the rear addition, stays within your volume allowance. Because L shaped designs use more of that allowance than a single dormer, it is worth checking the calculation carefully with your designer before assuming it fits.
Why are L shaped conversions so common in London?
Many Victorian and Edwardian terraced houses in London have a rear addition, sometimes called a return, which gives them the extra roof needed to build the second, smaller part of the L shape over. This feature is less common outside London terraces, which is part of why this style is so associated with the city.
How much extra space does an L shape give compared to a single dormer?
It varies by house, but because you are effectively adding two connected areas of usable roof space rather than one, an L shaped conversion often allows for two bedrooms, or a bedroom with a proper ensuite, rather than a single larger room.
Does every terraced house qualify for an L shape conversion?
No. You need an existing rear addition with its own roof for the second part of the L to sit over. A survey of your specific house will confirm whether this feature exists and whether it is suitable to build on.