New! ThermGard TG50 Roof Glazing System

  • Wide Spans
  • Low Pitch
  • Non-Fragile

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Lonsdale Roofing

ThermGard Self Supporting Glazing Bars

ThermGard Glazing Bars


Self Supporting Glazing Bars


​A neat 40mm wide box bar design, ThermGard provides a cost-effective alternative to more expensive sloped curtain walling systems without sacrificing aesthetics. Various slim-line box rafters are available to suit small or large spans. Alternatively the carrier rail may be mounted on top of continuous timber rafters – see our ThermGard-R glazing bars. A continuous screw on pressure plate with gaskets provides outstanding glass retention and a choice of decorative external covers are available to provide either contemporary glass roof appearance or a more traditional heritage style for roof lanterns on period buildings.

“Lonsdale is our ‘go-to’ company when we need a quality rooflight system” – Stuart Wood, Ingleton Wood Architects

Span Table

Section Single Glazing (mm) Double Glazing (mm)
ALM 100/1 3000 1900
ALM 100/2 3800 2900
ALM 100/3 4400 3600
ALM 100/4 5000 4000
ALM 100/5 5500 4500
ALM 100/H6 3000 1900
ALM 100/H7 4200 3450
ALM 100/H8 5000 4000

Please note the above table is for guidance only, for although the glazing bars can be used in compliance with the requirements of BS5516 ThermGard maximum recommend spans may not always comply. If in doubt please contact our Technical Department. A more detailed table is published in the LMC Design guide.

Glazing Width = Glazing Bar c/c minus 13mm or minus 15mm if using thermal barrier.

ThermGard is a tried and tested product installed throughout the UK. Some notable projects include The British Museum, Windsor Royal Opera House, ILVA stores, the US Ambassador’s Residence and McArthur Glenn Outlet Village, Bridgnorth.s.


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What is BS5516?

BS5516 is the global standard for two-edge and four-edge patent glazing systems that use glass and plastic glazing sheet materials. It provides structural and design recommendations, including the minimum thicknesses of glazing and the types of plastics to use. This regulation helps ensure that glazing is safe to be installed.  

What are gaskets?

Gaskets are continuous rubber seals which cushion the glass and provide a weather-tight seal. Without gaskets, water would trickle into your building and collect around the glazing, which can lead to deterioration and condensation. 

Why is ventilation important?

Ventilation is vital to prevent condensation build-up. Should condensation develop, mould will breed and may encourage the deterioration of the silicone seals that surround your glazing. Mould can be difficult to rid, especially when not treated properly. So, you should ensure that you have adequate ventilation in your rooms at all times.