Why are setting blocks necessary in glazing?

They support the dead weight of the glass, isolate the glass from the frame to prevent damage, and maintain proper edge clearances for thermal expansion.

How is the thickness of the glass selected?

Glass thickness is selected based on the surface area of the pane and the maximum design wind pressure it must withstand, using the charts/tables provided in the code.

What is the difference between edge cover and edge clearance?

Edge cover is the dimension of the glass that is covered by the frame/beading holding it in place, whereas edge clearance is the physical gap between the edge of the glass and the inside of the frame.

IS 4948

: 1994

Code of Practice for Glazing in Buildings

CurrentSpecializedCode of PracticeBIMArchitectural · Doors, Windows and Shutters

Archive.org BIS Portal Google

This code covers the guidelines for the selection of glass, glazing materials, and the execution of glazing work in buildings. It provides essential design considerations for wind loading on glass panels and specifies the required clearances and setting techniques to prevent stress concentrations and structural failure.

Provides recommendations for the selection and installation of glass and glazing systems in buildings.

Quick Reference Values

Minimum edge clearance for glass area < 0.5 sqm3 mm

Minimum edge cover for glass area < 0.5 sqm5 mm

Minimum front and back clearance2 mm

Minimum length of setting block25 mm

Setting block distance from corners1/4th of pane width (ideal)

Practical Notes

Always provide adequate edge clearance to accommodate the thermal expansion of glass; a lack of clearance is a primary cause of thermal cracking.

Setting blocks must be made of materials like neoprene or PVC (Shore A hardness 70-90) to properly transfer the weight of the glass to the frame without damaging the edges.

Glass thickness must be determined not just by aesthetic requirements but strictly by referencing the design wind pressure of the building location and height (IS 875 Part 3).