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Why framed glass rooflights are superior to frameless glass rooflights

Self-build & Renovation
Daylight Systems

Weather resistance

Frameless glass rooflights are characterised by their installation requiring no screws, and only a silicone seal below the glass.  This seal will be under constant attack from rainwater running under the glass and against the seal, risking a leak if the seal is penetrated over time.

In contrast, Brett Martin Flat Glass rooflights feature an aluminium frame with drip edge and integral water management system ensuring that, in the unlikely event the seal around the perimeter of the glass panel should fail, any rainwater will be guided out onto the roof surface and not into the building.

Thermal performance

Many frameless glass rooflights are promoted with reference only to the centre pane U-value of the glass panel in the vertical plane (like a window).  However, to ensure compliance with current building regulations in England, Scotland and Wales, the thermal performance of a rooflight should be calculated in the horizontal plane and consider the perimeter of the rooflight including the spacer bar and edge seal of the glass unit.

Brett Martin Flat Glass rooflights are highly thermally efficient with an overall U-value that is calculated in the horizontal plane in accordance with current building regulations, and this information is made available in product literature available from our website.


Given frameless glass rooflights are simply bonded to a builder’s upstand, they are much easier to break into than a mechanically fixed rooflight, and are highly unlikely to meet the security requirements within building regulations for the applications where they are often used, such as single story domestic flat roofs.

In addition to a weather seal, Brett Martin Flat Glass fixed rooflights are mechanically fastened to the roof with security screws.  They have been tested to the PAS24:2022 security standard and are Secured by Design accredited.


The Rooflight Association (formerly NARM) have received reports of multiple unsafe incidents related to frameless glass rooflights, including:

  1. Entire frameless rooflights being blown off the roof by the wind because they were only attached via an inadequate silicone seal that failed.
  2. The inner panes of frameless glass rooflights with a stepped edge falling into the room below because the inner pane wasn’t supported, and instead was hanging from the outer pane by a non-structural seal that failed.
  3. The inner pane of frameless glass rooflights without a stepped edge breaking due to contact with sharp screw heads in the upstand below the glass.  If the inner pane is laminated then the glass may not fall (assuming it is adequately bonded to the upstand), but many frameless rooflights on the market have a toughened inner pane that will fall in this scenario.

Brett Martin Flat Glass rooflights feature glass with laminated inner panes bonded into the aluminium frame with structural adhesive, meaning that there is no risk of damage to the inner pane from the upstand surface, and if the glass is broken for any other reason, it will be held within the frame that is mechanically fastened to the roof.  In addition, Brett Martin Flat Glass rooflights are non-fragile to CWCT TN67 for class 1 or 2 roofs (depending on size), ensuring anyone accessing the roof will not fall through the rooflight if accidentally fallen on.

For further information about the problems and hazards associated with frameless flat glass rooflights please look at the following resources from the Rooflight Association (formerly NARM) and the Advisory Committee for Roofsafety (ACR).


Brett Martin glass rooflights are the ideal way to create architecturally stunning daylight solutions for schools, public buildings, retail developments and homes, both new-build and refurbishment.