CREATIVE SIDE

Recent years have seen a surge in popularity of what have become known as ‘walk-on’ rooflights. These are very high specification glass structures designed to floor loadings and installed in-plane with external floors on roof decks and roof terraces where pedestrian access is unrestricted.

Notable examples can be seen as tourist attractions all over the world, on towers, bridges and other structures offering a high viewpoint. More recently, these ‘walk-on’ rooflights have become more widely available, with many now providing a means by which homeowners are able to improve space utilisation offered by roof areas.

Making the most of daylight

It’s an exciting prospect: a fully accessible roof terrace with transparent areas allowing abundant daylight into the room below, as well as a visual connection between the two floors.

Research has proven that natural daylight plays a vital role in supporting health and wellbeing, as well as providing strong aesthetic appeal and improved utility in interior spaces.

However, there are many points to consider with this type of installation.

Structural Considerations

Whilst there are many rooflight glazing options available in today’s market, the only suitable material for rooflights designed for deliberate foot traffic is glass of a very high specification, to CWCT (Centre for Window & Cladding Technology) Class O rating for non-fragility.

The outer pane must be both toughened and laminated, and must be specifically designed for the pane size and method of support. The outer pane will usually comprise 3 leaves laminated together, sometimes with an additional sacrificial annealed leaf on the outer surface, typically giving a total thickness of 30-40mm for the outer pane alone. This results in a product which is capable of withstanding floor loadings – and is therefore extremely heavy, weighing typically between 95 kg/m2 and 110 kg/m2. This must be correctly supported, so is not be suitable for roof structures which do not meet floor loading standards.

Polycarbonate or GRP glazing can NEVER be specified for applications designed for deliberate foot traffic. It’s also extremely important to note that rooflights with CWCT nonfragility ratings of Class 1, Class 2 or Class 3 are not designed for regular foot traffic and should never be considered for this type of application.

Roof access

As they are always installed as part of the roof structure, walk-on rooflights are fixed installations and therefore not suitable as a means of providing roof access. A variety of opening rooflight options are available to allow safe roof access via an internal staircase, but these are not suitable for regular foot traffic, so designs should take this into consideration.

Safety & privacy

Glass can become slippery when wet – a factor that should be taken into consideration when specifying walk-on rooflights. This is of particular importance when the glass is being installed in public spaces. However, on private dwellings it is less likely that the glass will be used if it is raining.

Applying an anti-slip glass surface finish can reduce the risk of slippages and the same finish can also provide some obscurity to the glass if required for privacy reasons.

A screen printed surface that includes particles within the ink to create a rough texture can be applied to the glass in a variety of patterns, which will significantly increase the slip resistance of the glass. Alternatively the surface of the glass can be sand blasted which will result in more diffused light to the areas below the rooflight. Other possibilities to explore…

Walk-on rooflights aren’t only for roof terraces. I’ve also seen some clever installations in gardens adjoining houses, where basement areas extend beyond the external walls of the property, as well as internal applications allowing light to pass between floors of a building.

Walk-on rooflights have revolutionised the way we perceive and utilise rooftop spaces. By offering enhanced accessibility, abundant natural light, high levels of safety, and customisable design options, they have become essential elements in many notable residential, commercial, and public settings. paul@daylightingmag.co.uk