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Are you Planning to Build a Loft Conversion in London?

Find out if you qualify for Permitted Development or if you need to apply for Planning Permission

Staircase leading to a dormer loft conversion

Permitted Development Rights is a Government scheme designed to get more homeowners to expand their existing properties. It allows some loft conversions to go ahead without the need for planning permission. To qualify, your conversion must fit within these guidelines:

* No part of the house can, as a result of the extension works, exceed the height of the highest part of the existing roof
* The expansion must not extend beyond the plane of any existing roof slope which forms the principal elevation of the house and fronts a highway
* The cubic content of the resulting roof space must not exceed the cubic content of the original roof space by more than 40 cubic metres in the case of a terrace house, or  50 cubic metres in any other case
* It must not include the construction of a veranda, balcony or raised platform; or the installation, alteration or replacement of a chimney, flue or soil and vent pipe    
* The materials used in any exterior work should be similar to those used in the construction of the exterior of the existing property
* Except for a hip and gable expansion, the extension must be set back at least 0.2 metres from the original eaves. No part of the extension should extend beyond the outside face of any external wall of the original house.
* Windows inserted on a wall or roof slope forming a side elevation of the house must always be obscurely glazed, and non-opening unless they are more than 1.7 metres above the floor.

These allowances include space previously added to the original house so if your loft has already been extended, that counts towards your cubic metres.

Homes that always require planning permission
Flats, maisonettes, listed buildings and properties in conservation areas are excluded from the development rights scheme, and their owners still have to apply for planning permission.

Dormer Loft Covnersion with Schuco Windows

Types of loft conversions
When it comes to expanding your loft space, there are four popular options for homeowners to choose from, each with its planning considerations.

Roof light loft conversion
Roof Light is the simplest type of loft conversion. It involves renovating the pitched roof to add in a couple of skylight windows such as Velux. The existing structure of the roof itself doesn’t change, and therefore, this type of extension doesn´t usually require planning permission.

Dormer loft conversion
These extensions have been popular for many years now as they create an additional room as well as extra headspace. They are added to a sloping roof at 90 degrees, they have a flat roof and vertical sides, creating a box-like shape. Most of the times, dormer conversions do not require planning permission. 

Roof Light Loft Covnersion with Velux Windows

Hip to gable loft conversion
With this type of loft conversion, a side of the house is extended by first removing part of the existing roof and erecting a triangular vertical wall, which is then connected via rafters and tiled over. Planning permission is often required with this type of conversion.

Mansard loft conversion
Mansard loft conversions are usually found at the rear of the property and are very popular in terraced houses. To build a mansard loft conversion, the roof is altered by adding a horizontal edge and a 70 degrees inwards inclined wall. This type of extension project usually requires planning permission.

If you are still unsure about whether or not you need planning permission, most construction companies in London will be able to advise you on every aspect of building a loft conversion, including planning regulations and permissions.

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