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A Guide to Flat Roof Windows & Skylights


6th April 2018

Rooflights are an ideal way to increase natural light into the room below. They not only allow you to reduce your dependency on artificial lighting but also encourage energy efficiency in the property. Sometimes a rooflight is a practical alternative when a vertical window cannot be installed onto a house or commercial building.

If you are considering installing a rooflight onto a new or existing roof, you will need to factor in its usage, aesthetic appeal and performance levels. Our guide to flat roof windows and rooflights covers every aspect to help you make a carefully informed buying decision.

What are Rooflights?

A 'rooflight' is an opening that is created in the structure of a flat roof to enable light to come into the interior space below. The term can also be referred to when talking about skylights or other forms of glazed openings.

Velux Rooflight - Roof Stores
Velux Rooflight

Skylights are a specialist product provided by companies who typically only provide this type of window, rather than the more conventional style. It's worth speaking to a professional for advice before making your final decision.

What Windows are Available for Flat Roofing?

As flat roofing is becoming a popular choice once again with designers and architects, the inclusion of roof lighting is also being seen more regularly. Property owners can choose from two main categories; off-the-shelf and custom-made solutions.

The former option provides rigid fixtures to fit into standard designs. The latter can be made to meet almost any requirement.


Polycarbonate rooflights are found at the cheaper end of the scale. These can also be used for venting in cold flat roof structures and come in either double or triple skin. The use of glass in the window will naturally raise the price but also increase its lifespan. Velux are usually the go-to supplier for almost every kind of glass roof window.

Another option is a ‘sun tunnel’, which channels light through a reflective tube into spaces below. This is ideal for rooms that struggle to naturally receive sunlight.


If required, a glazed rooflight can be reinforced to the point where it can be walked across safely. Retractable glazing can also be designed to completely open the internal space to the elements outside.

If you're looking for something a bit more unique, roof lanterns, domes and pyramid designs are available to create a far more unique look on the roof surface.

What to Consider When Buying Flat Roof Windows & Rooflights

The good news is that planning permission is rarely a requirement for flat roof windows or rooflights. This is because they are typically part of the extension agreement or a replacement for similar roof windows or rooflights. The same applies to a new addition to the flat roof, although it is always worth checking first with your local authority.

Roof Domes - Roof Stores
Roof Domes

Bespoke rooflights, such as pyramids or lanterns, may require permission as their elevated design and shape may fall into the eye line of neighbouring residents. When considering this option, look at the building regulations to verify how much glass is permitted for an individual structure.

Key Criteria

  • Rooflight Position: Where it will be installed and the function it will have are the next two things to think about. Over-exposure to UV can prove dangerous and this is a factor that must be taken into consideration for south-facing properties. Directional placement will affect the type of glass being used in the rooflight. It also determines whether you need glazing that includes higher levels of UV protection.
  • Sizing: This also ties in with the position of the rooflight. Larger sizes will naturally let more light into spaces below which will increase exposure to UV light. Balancing the amount of natural light coming in from the roof with vertical windows is also something to consider.
  • Access and Ventilation: While ventilation is required for cold flat roofs, it is always helpful to have it built into warm roofing, especially to help during the warmer months. A rooflight can help with this, while also providing a point of access to the surface of the roof. This makes it far easier to inspect and maintain throughout the year.
  • Upstands: The 'upstand' is the frame that sits around the rooflight. The general advice is to have the this created separately, rather than as one whole structure. A separately created upstand allows the roofing membrane to be installed without issue before the rooflight is installed. This will also ensure the correct pitch is in place for rainwater to naturally drain from the roof. Just as importantly, if repairs or replacements are ever a requirement, no damage can be caused to the structure of the roof.
  • Installation: When searching for an installation company, always check they are British Standards Institution (BSI) certified. This guarantees they adhere to industry standards. It will also give you peace of mind about the quality of work you will receive.

The Cost of Roof Lighting

Find out the most recent prices for our flat roof lighting & flat roof window solutions by following these links.

Standard, unglazed rooflights can start from as little as £250. These usually consist of materials such as polycarbonate as an alternative to glass.

Smaller glazed options start at around £400-£500, while bespoke rooflights can be priced from £700 upwards. If you are thinking of installing a walk-on unit or an electronic rooflight, you can expect to pay at least £1000.

What are the Advantages of Rooflights?

Apart from the obvious aesthetic appeal that flat rooflights provide there are numerous benefits that their installation can offer to the building and its inhabitants.

  • Energy Efficiency: This is of growing importance in the modern age, as we are all encouraged to find ways to be more efficient with our energy use to help the environment. With more daylight coming into the property, energy consumption can be reduced which will lead to lower bills. This is invaluable to both private residents and business owners, especially during winter costs inevitably rise.
  • Ventilation: Rooflights are an easy way to increase ventilation in the property. This is ideal for cold flat roofs that require additional ventilation by law. During the warmer summer months, this will help cool the house when temperatures are normally higher in the living spaces.
  • Privacy: With the installation of a rooflight, you can take advantage of increased sunlight while also maintaining the privacy of your home or business. This is particularly helpful for anyone living close by to other residents. It's also a consideration for companies who require protection over the type of work taking place on their premises.
  • Roof Access: Every flat roof requires basic maintenance and rather than using an external ladder or spending money on a professional to head up to the roof, a rooflight allows access to the surface for checks at any time.

Maintaining Rooflights & Windows

Due to their positioning and nature of the materials used, rooflights are likely to collect dirt and stains. There are more pricey options available such as self-cleaning glass - which reduce the maintenance levels required. However, for those who have standard glazing in their rooflights and want to understand the best maintenance procedures, there are a few simple steps to follow throughout the year.

Roof Lantern - Roof Stores
Roof Lantern

  • Glass Cleaning: As you would with standard roof checks, a six-monthly inspection of the rooflight and subsequent manual cleaning of the surface with a wet, soapy cloth or glass maintenance product will help keep the exterior of the glass in good condition. For the interior, wipe away any dirt using a similar method on the windows as you did for the outside.
  • Condensation Prevention: This is less of a problem with warm flat roofs, and cold flat roofs should also have in-built ventilation to help warm air leave the building. Using an extractor fan in the kitchen and bathroom will also help prevent rising moisture up onto the glass.
  • Checking for Leaks: Gaps appearing in the rooflight structure will usually come from damaged windowsills, poor flashing or siding installation. A professional roofing company should be called to assess the damage to have this repaired as soon as possible.



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