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For information about the guidance on this page and how it should be applied, visit Using this SPD.
Where proposals deviate from the guidance here, the Council will need to be satisfied that proposals are high quality and not detrimental to neighbourhood amenity. Pre-application submission is encouraged.
Rooflight added to loft extension in Walthamstow (deDraft Architects. Photography: Whitaker Studio)
7.9 Loft extensions and roof alterations
Roof alterations such as dormers, rooflights and loft extensions can provide additional light and space to a home. A dormer is a window set within a structure, which projects through a sloping roof.
7.9.1
For details of permitted development rights for loft extensions and roof alterations to houses, refer to this page on the Planning Portal. If the proposal does not fulfil the criteria stated here, planning permission will be required.
7.9.2
It may be possible to add a loft extension or make roof alterations to top-floor flats. For details of permitted development rights for flats, refer to this page on the Planning Portal.
7.9.3
For all roof extensions and alterations, spaces must comply with the Nationally Described Space Standard, as reflected in both the London Plan and Local Plan, in terms of room heights and internal floor areas.
7.9.4
Proposals for roof extensions and alterations should use materials of the highest quality available. Proposals should reflect the architectural character of the existing roofscape, in terms of proposed form, features and materials.
7.9.5
Where homes have already been extended, consideration will be given to the cumulative impact on character and neighbouring amenity.
Rear roof dormer, set in minimum 0.25m from the eaves and ridge, and 0.5m from the roof sides
Rooflights
7.9.6
Where planning permission is required, proposals for rooflights must:
be subordinate features on the roof.
not extend more than 0.15m above the slope of the original roof, or ideally be flush.
7.9.7
In conservation areas, conservation-style rooflights are required, which sit flush with the roof.
7.9.8
For terraced houses, there should be no more rooflights to the front than the number of windows on the front elevation.
7.9.9
Where possible without compromising internal layouts, new rooflights should line up with windows below, in order to create a more balanced elevation.
Dormers
7.9.10
Front dormers are typically not supported, except in certain circumstances where proposals reflect the existing character of the area and can demonstrate that they are of exemplar design quality. This is supported by Policy 53 of the Local Plan, ‘Delivering High Quality Design’.
7.9.11
Where planning permission is required, roof dormers should be set in at least 0.25m from the ridge and eaves and at least 0.5m from the roof sides. Set-ins should be proportional to the roof size. This helps to ensure that extensions remain subservient to the host dwelling.
7.9.12
Rear dormers in properties within conservation areas may be supported, where proposals can demonstrate that they are of exemplar design quality. This is supported by Policy 53 of the Local Plan, ‘Delivering High Quality Design’, and Policy 72, ‘Conservation Areas’.
7.9.13
For proposals in conservation areas, rear roof dormers must be set in at least 0.25m from the ridge and eaves and at least 0.5m from the roof sides. This helps to ensure that roof dormers remain subservient to the host dwelling.
7.9.14
Where planning permission is required, rear L-shaped dormers or rear dormers in unaltered terraces may be supported where proposals reflect the existing character of the area, and can demonstrate that they are of exemplar design quality.
7.9.15
Where a property has been extended to the side, a single dormer should not span the full roof width. To help retain balance and regularity of roof forms along the street, the dormer width should be restricted to the width of the original roof, or two smaller dormers added.
7.9.16
Proposals for side dormers on hipped roofs will only be supported if they do not overlook neighbours or adversely affect street scene. Side dormers should be well-inset so as to remain subservient to the host dwelling.
This project by in North London includes rear single storey extension and rear dormer (Neil Dusheiko Architects. Photography: Edmund Sumner)
Raising the roof ridge
7.9.17
Making sustainable alterations to roofs can involve the raising of a roof ridge. Applications will be supported when the applicant can demonstrate that the proposal would not be detrimental to the streetscape, through visualisations, elevations, sections or other appropriate drawings.
Hip-to-gable roof extensions
7.9.18
Proposals for hip-to-gable roof extensions are not usually approved, unless there are established patterns of this in the immediate surrounding area. To be considered, proposals must be of exemplar design quality and demonstrate that the symmetry of the building or terrace would not be negatively impacted, through visualisations, elevations, sections or other appropriate drawings.
Mansard roof extensions
7.9.19
Mansard roofs are not a typical or characteristic roof profile in the borough and it is therefore unlikely that this type of extension will be appropriate. Mansard roofs may be supported where proposals reflect the existing character of the area, and can demonstrate that they are of exemplar design quality.
Rear dormer and outrigger roof extension in Leytonstone (Mike Tuck Studio)
Learn about the retrofit ideas above, and other retrofit measures, using the links below:
For information about the guidance on this page and how it should be applied, visit Using this SPD.
Where proposals deviate from the guidance here, the Council will need to be satisfied that proposals are high quality and not detrimental to neighbourhood amenity. Pre-application submission is encouraged.
Rooflight added to loft extension in Walthamstow (deDraft Architects. Photography: Whitaker Studio)
7.9 Loft extensions and roof alterations
Roof alterations such as dormers, rooflights and loft extensions can provide additional light and space to a home. A dormer is a window set within a structure, which projects through a sloping roof.
7.9.1
For details of permitted development rights for loft extensions and roof alterations to houses, refer to this page on the Planning Portal. If the proposal does not fulfil the criteria stated here, planning permission will be required.
7.9.2
It may be possible to add a loft extension or make roof alterations to top-floor flats. For details of permitted development rights for flats, refer to this page on the Planning Portal.
7.9.3
For all roof extensions and alterations, spaces must comply with the Nationally Described Space Standard, as reflected in both the London Plan and Local Plan, in terms of room heights and internal floor areas.
7.9.4
Proposals for roof extensions and alterations should use materials of the highest quality available. Proposals should reflect the architectural character of the existing roofscape, in terms of proposed form, features and materials.
7.9.5
Where homes have already been extended, consideration will be given to the cumulative impact on character and neighbouring amenity.
Rear roof dormer, set in minimum 0.25m from the eaves and ridge, and 0.5m from the roof sides
Rooflights
7.9.6
Where planning permission is required, proposals for rooflights must:
be subordinate features on the roof.
not extend more than 0.15m above the slope of the original roof, or ideally be flush.
7.9.7
In conservation areas, conservation-style rooflights are required, which sit flush with the roof.
7.9.8
For terraced houses, there should be no more rooflights to the front than the number of windows on the front elevation.
7.9.9
Where possible without compromising internal layouts, new rooflights should line up with windows below, in order to create a more balanced elevation.
Dormers
7.9.10
Front dormers are typically not supported, except in certain circumstances where proposals reflect the existing character of the area and can demonstrate that they are of exemplar design quality. This is supported by Policy 53 of the Local Plan, ‘Delivering High Quality Design’.
7.9.11
Where planning permission is required, roof dormers should be set in at least 0.25m from the ridge and eaves and at least 0.5m from the roof sides. Set-ins should be proportional to the roof size. This helps to ensure that extensions remain subservient to the host dwelling.
7.9.12
Rear dormers in properties within conservation areas may be supported, where proposals can demonstrate that they are of exemplar design quality. This is supported by Policy 53 of the Local Plan, ‘Delivering High Quality Design’, and Policy 72, ‘Conservation Areas’.
7.9.13
For proposals in conservation areas, rear roof dormers must be set in at least 0.25m from the ridge and eaves and at least 0.5m from the roof sides. This helps to ensure that roof dormers remain subservient to the host dwelling.
7.9.14
Where planning permission is required, rear L-shaped dormers or rear dormers in unaltered terraces may be supported where proposals reflect the existing character of the area, and can demonstrate that they are of exemplar design quality.
7.9.15
Where a property has been extended to the side, a single dormer should not span the full roof width. To help retain balance and regularity of roof forms along the street, the dormer width should be restricted to the width of the original roof, or two smaller dormers added.
7.9.16
Proposals for side dormers on hipped roofs will only be supported if they do not overlook neighbours or adversely affect street scene. Side dormers should be well-inset so as to remain subservient to the host dwelling.
This project by in North London includes rear single storey extension and rear dormer (Neil Dusheiko Architects. Photography: Edmund Sumner)
Raising the roof ridge
7.9.17
Making sustainable alterations to roofs can involve the raising of a roof ridge. Applications will be supported when the applicant can demonstrate that the proposal would not be detrimental to the streetscape, through visualisations, elevations, sections or other appropriate drawings.
Hip-to-gable roof extensions
7.9.18
Proposals for hip-to-gable roof extensions are not usually approved, unless there are established patterns of this in the immediate surrounding area. To be considered, proposals must be of exemplar design quality and demonstrate that the symmetry of the building or terrace would not be negatively impacted, through visualisations, elevations, sections or other appropriate drawings.
Mansard roof extensions
7.9.19
Mansard roofs are not a typical or characteristic roof profile in the borough and it is therefore unlikely that this type of extension will be appropriate. Mansard roofs may be supported where proposals reflect the existing character of the area, and can demonstrate that they are of exemplar design quality.
Rear dormer and outrigger roof extension in Leytonstone (Mike Tuck Studio)
Learn about the retrofit ideas above, and other retrofit measures, using the links below:
Rooflight added to loft extension in Walthamstow (deDraft Architects. Photography: Whitaker Studio)
Rear roof dormer, set in minimum 0.25m from the eaves and ridge, and 0.5m from the roof sides
Rear dormer and outrigger roof extension in Leytonstone (Mike Tuck Studio)