Technical guides
Commercial glazing technical guides
Plain answers to the questions that decide a specification — written so they can be read once and acted on, not so they fill a page.
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- Fixed written quotation
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- Commercial specialists only
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Stick vs unitised curtain walling
Stick curtain walling is assembled from loose components on site; unitised curtain walling arrives as factory-glazed storey-height cassettes. Stick is cheaper and more forgiving of an imperfect frame. Unitised is faster on site and seals better.
Fire rated glass ratings explained
Fire glazing is classified under BS EN 13501-2. E means integrity — it holds back flame and hot gases. EW adds a limit on radiated heat. EI adds insulation, keeping the unexposed face cool. The number is the tested minutes.
Part K critical locations
Building Regulations Part K requires safety glass in critical locations — broadly, any glazing below 800mm from floor level, and any glazing within 300mm of a door edge up to 1500mm from floor level, where impact is likely.
U-values and Part L for commercial glazing
Part L is assessed on the whole window or the whole facade, frame included — not on the centre-pane figure printed on the unit label. A 1.0 W/m²K unit in a weakly broken aluminium frame commonly gives a whole-window figure nearer 1.6.
Acoustic glazing and what it costs
A standard 4-16-4 double glazed unit gives roughly 30dB of sound reduction. An asymmetric acoustic laminate build-up reaches 38–42dB, and secondary glazing with a wide air gap can exceed 45dB.
Laminated vs toughened glass
Toughened glass is stronger before it breaks and disintegrates into blunt granules when it does. Laminated glass is weaker on impact but holds together on its interlayer, keeping the opening closed and the building secure.
Why double glazed units mist up
A double glazed unit mists when the edge seal fails and moist air enters the cavity. The desiccant in the spacer bar saturates, and condensation forms between the panes. The unit cannot be resealed and must be replaced.
Glass balustrade loadings explained
BS 6180 sets a horizontal line load at handrail height according to how the building is used: 0.74 kN/m for offices and residential, 1.5 kN/m for retail and assembly, and 3.0 kN/m where crowding is expected.
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