Rooflight & Patent Glazing Glossary

Not all building professionals are familiar with the correct terminology for rooflights and patent glazing. So, let us help with that!

Richard Burgess, Managing Director of Lonsdale Metal Co Ltd with over thirty years industry experience, sets out commonly used terms and their correct definitions below:

Bead

Continuous section to retain the glass usually combined with a gasket

Cill

Section at foot of the glazing

Curtain Walling

Four edge support cladding system comprising of rafters and transoms for sloped & vertical glazing

Cap / Capping

Screw on or clip in continuous section to retain the glass

Drainage Channel

Water channel integral within a glazing section to discharge any water to the outside the building

Fastener

Screw or bolt to fasten components

Came

Horizontal section to join two pieces of glass

Curb

Raised upstand around the structural opening to provide fixing for roof light.

Eaves

The point where sloped glazing meets the vertical

Fixing Shoe / Slipper

Bracket to fix a glazing bar to the structure which maybe fixed or sliding

Fixing

Screw or bolt used to fix the glazing system to the supporting structure

Four Edge Support

The system, where the glass is retained on all four sides e.g., sloped curtain walling

Gasket

Usually a flexible and yielding strip used to provide a water and air-tight seal the glass and glazing bead or capping.

Glazing Bar

Longitudinal supporting member that spans between structural supports & incorporates drainage channels

Patent Glazing

Two edge support glazing system for sloped & vertical glazing

Flashing

Usually lead or aluminium pressing to provide weather-tight seal with the abutments to the building or at the ridge and hips on a roof lantern

Framless

Glass structure usually bonded with silicone without the need of a supporting frame. Sometimes referred to as ‘structural glazing’

Glass / Glazing Stop

Bracket to prevent glass sliding or slipping usually at end of glazing bar

Hip

A sloping member providing support to two sloping planes of glass

Keel Bar

A glazing bar with strengthening fin below the glass

Muntin Bar

non-structural horizontal section for joining glass

Ridge

A parallel structural member providing support to two panes of sloping glass

Gable

The vertical triangle formed at the end of duo-pitch glazing

Head

Top of sloped glazing

Infill

glazing material most commonly glass or polycarbonate, but may be insulated aluminium panel or GRP sheeting

Pitch/h2>
The angle of the glazing to the horizontal

Roof Lantern

Usually hipped rooflight for fitting onto flat roofs

Spacing

The span between glazing bars i.e. width of panes

Storm Cleat

Clip to improve retention of the glazing bead in exposed locations with high wind loads. Most often used on vertical patent glazing.

Transom

The horizontal members in curtain walling and other four edge support sloped glazing systems

Span

The distance from top to bottom of the glazing slope

Stalk

The vertical part of a glazing bar that gives the section rigidity

Two Edge Support/h2>
The horizontal members in curtain walling and other four edge support sloped glazing systems

Wing

Continuous section or bead to retain the glass

Setting Block

Plastic or rubber block to cushion the edge of the glass

Thermal Barrier

Usually plastic or polyamide section to prevent heat transfer from inside to outside of the rooflight thus reducing risk of condensation

WEATHER SEAL

Gasket or sealant to prevent water ingress