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Class B – additions to the roof of a house


dormers in roofsThe General Permitted Development Order (GPDO) allows for roofs to be added to with dormers or loft conversions on many homes without the need for any planning. Needless to say there are a few restrictions, which we will cover in this article.  Despite not requiring planning, you will require building regsClass C which also relates to roofs covers the installation of Velux windows on other parts of roofs. The insides are classed as internal works and not development and is therefore allowed as it is outside of the GPDO.

All these permissions are contained within Part 1 of the GPDO. Before starting work check to see if there any conditions that have been placed on your property. These are quite common on new build properties or maybe as a result of a previous planning approval. In those cases full planning permission might be required relevant to that condition or restriction.

Once you have built your loft conversion enjoy it or you can choose to submit an optional application for a Lawful Development Certificate (LDC) which might be useful when you come to sell the property.


What about the internal loft or attic space?


Any changes to the internal space is not normally classed as development, therefore you do not require any form of planning consent. This includes the loft or attic space.  You will of course require building regulations and if in a listed building full consent from the conservation officer. If in doubt consult with your local planning authority. If altering the loft space of a flat, ensure that you own the roof void and that you also have the freeholders permission. Note that external alterations on a flat would normally require planning permission.


Where else can’t we benefit?


These permissions do not apply to flats or maisonettes. Nor do they apply to houses that have been converted from agricultural buildings, storage, light industrial, shops or casinos. They do however apply to houses (not flats) converted from offices under Class O. There are also restrictions if the building is listed, in a conservation area, AONB, Broads or Heritage site. They might also have been removed as a result of an Article 4 or a condition on a previous planning application. Finally alterations to the roof are to the original building or as it was on 1st July 1948, so this means you can’t add on a dormer to an extension built under permitted development.


You have said where we can’t – so what can we do?


Glad you asked!  There are a few limitations, but as long as you keep to the elements below, then enjoy your new loft or roof extension.

    • A volume allowance of 40 cubic metres additional roof space for terraced houses
    • A volume allowance of 50 cubic metres additional roof space for detached and semi-detached houses
    • No extension beyond the plane of the existing roof slope of the principal elevation that fronts the highway
    • No extension to be higher than the highest part of the roof
    • Materials to be similar in appearance to the existing house
    • No verandas, balconies or raised platforms
    • Side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor
    • Roof extensions not on article 2(3) land – conservation area, AONB, Broads
    • Roof extensions, apart from hip to gable ones, to be set back, as far as practicable, at least 20cm from the original eaves
    • The roof enlargement cannot overhang the outer face of the wall of the original house.


Also see Permitted development rights for householders – Technical Guidance


Updated: 6th July 2020 to add link to Technical Guidance

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