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    Roof Windows and Planning Permission:
    The Ins and Outs

    arrow Back to blog 14th May 2022

    In England and Wales, you do not normally need to apply for planning permission for the insertion of new roof windows subject to the current limits and conditions stipulated by the government’s Planning Portal under Schedule 2, Article 3, part 1, class C permitted development.

    When exploring home improvement options, considering aspects such as regulations, options, planning permissions and general suitability of ideas can become overwhelming. If you’d like to add a skylight to your home for extra light or ventilation, this article should help you understand the ins and outs of roof windows and planning permission.

    Does a skylight need planning permission?

    In England and Wales, you don’t normally need to apply for planning permission for the insertion of new roof windows subject to the current limits and conditions stipulated by the government’s Planning Portal under Schedule 2, Article 3, part 1, class C permitted development.


    This includes:

    • Any alteration cannot project more than 150 millimetres from the existing roof plane i.e. any new flat roof skylights cannot project more than 150 millimetres.
    • No alteration can be greater than the highest part of the existing roof.
    • Side-facing windows must be obscure glazed with any opening made 1.7 metres above the floor.


    The Planning Portal

    Established by the UK government, The Planning Portal allows you to check requirements and apply for planning permission online. Building regulation documents set out requirements for extensions, adding or removing skylights of all kinds.


    If your project fails to comply with one or more requirements, your development will not be permitted; a second application would need to be resubmitted, following amendments to your plans.


    Installation of a new rooflight will generally need approval under the Building Regulations for the following reasons:

    • The roof structure will often need to be altered to create the opening for a new rooflight.
    • The roof will have to be able to carry the weight of the new skylight. If it cannot do so it will need to be strengthened before installation.


    Changes to existing Skylights

    The removal, addition or alteration of a skylight can potentially impact how a roof works, resulting in unplanned movement. When making any aesthetic improvements to your roof care must be taken to ensure the roof continues to perform as it should and without any movement.


    Building regulations for roof windows

    Even if planning permission for a new roof window is not required, building regulations cannot be ignored. There are two sets of building regulations for roofs; work on an existing roof and the construction of a new roof e.g. for an extension. By law, any building or structural modification work must comply with building controls which stipulate minimum standards for design and safety.


    Be sure to pay particular attention to Parts J and L of Building Regulations; covering:

    • Energy efficiency
      • The U-value – In terms of energy performance, any window or door must comply with the minimum requirements of the Building Regulations in relation to the amount of heat that can pass through a window or door, including the frame. – Building regulations document L-1B, Table 1
      • At Sunsquare we can accurately calculate the U-value of each of our BSI-accredited skylights
    • Thermal insulation
      • Any rooflight installed must prove it has sufficient insulation against heat loss with effective energy performance.
    • Protection of buildings against the threat of fire.
      • In the event a skylight is in close proximity to a boundary, its fire performance must also be taken into consideration.


    Roof lights FAQs

    Can I put a skylight on a pitched roof?

    Yes, from 20 to 60 degrees angled roofs. Our new Aero Pitch Skylight is the most advanced pitched rooflight on the market. With all the reliability, smart technology and thermal efficiency developed by Sunsquare.


    What’s with skylight condensation?

    Skylight condensation occurs most frequently when warm, moist air rises to the ceiling and comes into contact with the colder glass surface that’s influenced by outside temperatures and weather conditions. There is also a danger that skylight condensation can form on more than just the glass pane.


    The root cause of skylight condensation is the conversion of vapour into liquid. When pockets of air become saturated with moisture, it is released in the form of water droplets. The condensation is easily identifiable by the mist-like conditions that form and cloud the interior glass pane of any low-value, poorly manufactured rooflight.


    We contribute more water vapour or humidity into our internal atmosphere by doing the simplest things; all of which can accrue on roof windows and skylights as condensation, including:

    • Cleaning
    • Showering (the main culprit for bathroom skylight condensation)
    • Cooking
    • Everyday breathing
    • Human perspiration


    To learn more, check out our article on the pitfalls of skylight condensation and how to avoid it.


    What do I need to measure when checking size requirements?

    This depends on whether you’re utilising the supplied uPVC 150mm upstand or creating a timber kerb.


    If you’re constructing a timber kerb, it should be at least 150mm tall, and the size of the rooflight you buy should equal the external upstand dimension, so a 600x600mm glass rooflight will need a 450x450mm hole made (75mm wide each side timber kerb gives you an external size of 600x600mm).


    If you use the supplied Upvc kerb, the hole you cut in the roof is the size you order, for example, a 600x600mm glass rooflight requires a 600x600mm hole.


    Flat vs Pitched glass rooflights

    While terminology for a glass-covered hole in the roof tends to be interchangeable when discussing the difference between rooflights and skylights, the types of these windows vary as well.


    Flat and pitched roof lights depend on the roof they are placed within.


    Flat skylights

    Flat skylights can be mounted at a pitch of 2 to 15 degrees. Most roofs have at least a 2-degree angle in order to drain rainwater. We can pitch windows accordingly in cases such as a ballasted roof, where the roof is entirely flat. Take a look at the Sunsquare range of flat skylights for inspiration for your development.


    Pitched skylights

    For roofs with a pitch of 20 to 60 degrees, pitched skylights are perfect for bringing natural light into a space that may not have access to room on walls for standard windows.
    Our new Aero Pitch Skylight is the most advanced pitched rooflight on the market with all the reliability, smart technology and thermal efficiency developed by Sunsquare over years.

    With a range of seven fixed sizes and bespoke options available, the Aero Pitch can seamlessly integrate into any space. A variety of glazing options allows you to design lighting aspects of the room, and whether you choose UV protection or tinted glazing, all Sunsquare skylights have a laminated inner pane as standard. We are leading the way in providing a safer and more secure skylight.


    If you’re at the planning stage of your project, please don’t hesitate to contact us to discuss your glazing requirements in greater detail. Call our experienced team today or drop us a line using our online contact form.


    Sign up for our whitepaper on building regulations. Written to help architects, surveyors and home improvers alike understand every UK building regulation.

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