Glass Installation Fundamentals
Setting blocks, edge clearance, face clearance, bite, expansion joints, and thermal stress management.
- Explain the purpose and placement of setting blocks
- Define edge clearance, face clearance, and bite and their minimum requirements
- Describe thermal stress causes and prevention methods
- Identify expansion joint requirements in glazing systems
- State the rules for glass-to-metal and glass-to-glass contact prevention
Lesson 1
Setting Blocks & Placement
Purpose of Setting Blocks
Setting blocks support the weight of the glass at the bottom of the frame opening. They prevent the glass from resting directly on the metal frame, which would cause point loading, stress cracks, and seal damage. Setting blocks are typically made of neoprene, EPDM, or silicone with a durometer (hardness) of 80-90 Shore A.
Block Placement
Setting blocks are placed at quarter points - one-quarter of the glass width from each edge. This distributes the glass weight evenly to the frame and prevents the bottom rail from deflecting.
For fixed glass: two blocks at quarter points from each end
For operable windows: placement varies by hardware type and manufacturer
Never Center a Single Block
A single setting block centered under the glass concentrates the entire weight at one point, causing frame deflection and potential glass breakage. Always use two blocks at quarter points for proper weight distribution.
Setting blocks support glass weight and prevent metal contact. Use two blocks at quarter points from each edge. Block material should be 80-90 Shore A durometer. Never center a single block under the glass.