Property News - July 09

Shining some light on planning issues for rooflights and dormers.

Choosing the right dormer or rooflight for traditional Properties

What do Planners and Conservation Officers look for in a planning application?

When converting an attic or adding an extension to a historic or traditional property, a key issue is the provision of natural light and ventilation. In order to secure Listed Building Consent or Planning Permission an appropriate arrangement of dormers and/or rooflights will be required. What is appropriate depends very much on what type of roof is proposed - its size, angle, height and relationship to the roof.

Dormers of Rooflights? Many people prefer dormers because they contain normal vertical windows which one can stand in front of to see out. However there is a limit to the number of dormer windows a roof elevation can accept, and there are many situations where use of a dormer is not appropriate, either because there is not enough space for it, or because the disposition of the roofs or windows below would make it look awkward or 'out of focus'.

Whereas dormer windows are regarded as architecture with a capital 'A' - i.e. they are seen as significant architectural elements, rooflights take a subsidiary role in the architecture of a building and are therefore a less conspicuous way of providing light and ventilation. Moreover rooflights are considerably less costly than dormers, and they provide more light - about 20% more than the equivalent sized vertical window - on account of the fact that they point upwards towards the sky.


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Generally speaking windows look better when they get slightly smaller on their way up an elevation. This is not always the case, but it is a good rule of thumb to follow. So the windows framed by dormers should ideally be a little smaller than the windows of the floor below if visual harmony is primary. The shape and style of the dormers should closely follow local architecture; if the there have been no dormers on the property before, neighboring properties will provide a good pointer for the overall design.

As to rooflights, these need to be sensitively detailed if they are not to detract from the roof of a historic building. Generally speaking the look of original cast iron Victorian rooflights is preferred, as these lie more or less flush to the adjoining roof tiles, whereas many modern roof windows stand somewhat proud of the roof and are chunky in appearance. Further characteristics of this type of rooflight include relatively fine glazing bars and the glazing is generally split into long narrow sections. Rooflights of this type are readily available today and are called 'Conservation Rooflights'; details can be found easily on the web by typing in this term.

Barn Conversions

When converting barns or stables, dormers are simply not appropriate as they would never have appeared on agricultural buildings of this nature. Rooflights can work very well, but there are two rules to ensuring appropriate intervention. Firstly the rooflights should be set out in a random way - not in a row and secondly there should be variation in size. As barns are part of our vernacular architecture, a formal or 'tidy' approach will simply look out of place.

Planning Rules and Employing an Architect

If your home is Listed, you will always require Listed Building consent; the first step is to speak to your local Conservation Officer. If your property is in a Conservation Area, certain rules apply, but you may not require Planning Consent under Class C of the Permitted Development Order 2008. The only way to be absolutely certain is to consult the local Planning Department. If you are employing the services of an architect, check their website for past projects demonstrating additions and extensions to Listed Buildings. Better still, if it is by personal recommendation, ask to see a couple of their previous work. If they have a good record of obtaining Planning Consent, this will give you greater confidence in their ability to achieve a successful outcome for you.


It is always best to check with your local Planning Department regarding Planning Permission. If you are in a Conservation Area, you may not require it. Check on for planning informationDormers should generally be smaller the further up the building they are placedEnsure you have a 'conservation rooflight' of an appropriate size, as modern rooflights do not have the correct featuresCheck out potential architects' websites for previous success in obtaining Listed Building Consent or Planning Permission

Peter King RIBA Co-Chairman, the Rooflight Company

Press Contact: Valerie King, Tel: 01993 833110

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