Design Guide

• Back to PLANNING

• Introduction
• The design of the garden suburb
• New Hampstead Garden Suburb Trust
• Barnet Council
• The Trust and the Council
• Extensions
• Building materials and details
• Walling materials
• Tiles
• Roofs
• Dormer windows & loft conversions
• Gutters and pipes
• Chimneys
• Porches
• Windows and doors
• Garages and parking spaces
• Garden buildings
• Fences, walls and hedges
• Landscaping and trees
• Satellite dishes
• Shopfronts and advertisements
• Listed buildings
• Glossary
• Making applications to:
• The Trust
• Barnet Council
• Additional information

Dormer windows and loft conversions

To create a picturesque external appearance, roof eaves on early houses were often brought down below bedroom ceiling level. This meant that dormer windows were needed at first floor level. These often had small tiled roofs or else lead flat roofs designed as part of the overall roofscape. ‘Half dormers’, with the lower part of the window set into the wall and the head breaking through the roof eaves, are also common. Modern dormers tend to be made too large in order to maximise internal space. As a result, detailing is often clumsy and heavy. New or replacement dormers must match the originals exactly but should comply with modern Building Regulations and thermal insulation standards. Nothing is less convincing than a ‘near match’ side by side with an original.

Many house holders apply to convert large roof spaces. There are several instances of unsatisfactory loft conversions with vast boxed-out dormers which were carried out in the 1960s before the strict controls of today were in place. Such applications would now be resisted.

As part of a loft conversion, dormers in the front of the roof may be suitable, depending on circumstances. Dormers will be expected to be in proportion with the size of the roof, without overbalancing, or dominating elevations, and with designs complementing the style and appearance of the house,. We will carefully consider whether a proposed dormer creates a precedent, for example, in a group of houses. An important consideration will be the effect of the dormer on the character and appearance of the property, the street and where relevant the group of properties of which is forms a part. Small cottages are generally designed be two-storey buildings only: loft conversions with dormers windows will often seriously affect their character and will generally be unacceptable.

On a larger house appropriately sited and designed dormers are generally acceptable. If sited to the rear or side, care must be taken to ensure that a significant increase in overlooking of neighbouring properties is avoided. In the case of a semi-detached property, particularly if symmetrical, care will be taken to ensure that a dormer window does not unbalance the pair.

If you have an original attic rooflight, this does not mean that you can automatically install a dormer in the same location. Similarly, insensitive and possibly unauthorised dormers in neighbouring properties will not necessarily be accepted as an argument for the installation of a dormer in your property. To enable your proposals to be fully assessed, please provide large scale drawings. These should show constructional details to a scale of 1:10 or1:15 for the Trust and 1:20 for the Council.

Small traditional rooflights may be acceptable in discrete locations, generally one per roof slope, offering an alternative to a dormer on modest properties. Their use on front roof slopes will be considered carefully to ensure that the character of the properties is not compromised. Modern rooflights in deep frames, which break up the line of the roof surface, are not considered acceptable.

Flat top ‘crown roofs’ on Suburb properties may allow the fitting of concealed top skylights.

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