Loft Conversion Permitted Development - without planning - the consent you may already
A sites permitted development rights are a very useful tool for building a loft
conversion without the requirement to obtain formal planning permission first. Most planning officers view a house
owners permitted development rights as the ‘anti-Christ’ of residential development as they do not have control
over what the house owner can build onto their property.
In many situations I can understand this thinking. Everyone must have seen those ugly big box dormers on the
rear of properties that have no intrinsic design value at all - in fact may must have devalued the properties
values as they are so poorly designed and constructed.
However, that said, most planners will only approve very small dormer windows that do not add any head height
space so you can understand a house owners frustration for when their scheme does require formal planning
When permitted development rights are used for a loft conversion it can take the subjective approval element
right out of the planners hands which can free up the design options for the homeowner and house extension designer
or architect as well.
Therefore, the homeowner should be mindful of which route they intend to take for their loft conversion - using
the sites Permitted Development rights or obtaining formal planning consent as the design options for each route
will be completely different.
Using permitted development for a loft conversion even allows for a hip to gable end roof extension within
certain circumstances which can be a very clever and practical route to achieving extra space within a loft
conversion. This can often be preferable in design terms than adding a big box carbuncle of a dormer to the rear of
The requirements of converting or extending the roof of a dwelling house for a loft conversion falls under Class
B of the latest GPDO of the planning legislation. Here is what it says word for word:-
B. The enlargement of a dwelling house consisting of an addition or alteration to its roof.
Development not permitted
B.1 Development is not permitted by Class B if—
(a) any part of the dwelling house would, as a result of the works, exceed the height of the highest part of the
(b) any part of the dwelling house would, as a result of the works, extend beyond the plane of any existing roof
slope which forms the principal elevation of the dwelling house and fronts a highway;
(c) the cubic content of the resulting roof space would exceed the cubic content of the original roof space by
(i) 40 cubic metres in the case of a terrace house, or
(ii) 50 cubic metres in any other case;
(d) it would consist of or include—
(i) the construction or provision of a veranda, balcony or raised platform, or
(ii) the installation, alteration or replacement of a chimney, flue or soil and vent pipe; or
(e) the dwellinghouse is on article 1(5) land.
B.2 Development is permitted by Class B subject to the following conditions—
(a) the materials used in any exterior work shall be of a similar appearance to those used in the construction
of the exterior of the existing dwellinghouse;
(b) other than in the case of a hip-to-gable enlargement, the edge of the enlargement closest to the eaves of
the original roof shall, so far as practicable, be not less than 20 centimetres from the eaves of the original
(c) any window inserted on a wall or roof slope forming a side elevation of the dwellinghouse shall be—
(i) obscure-glazed, and
(ii) non-opening unless the parts of the window which can be opened are more than 1.7 metres above the floor of
the room in which the window is installed.
Interpretation of Class B
B.3 For the purposes of Class B “resulting roof space” means the roof space as enlarged, taking into account any
enlargement to the original roof space, whether permitted by this Class or not.