Glazing (C-17) · Lesson 3 of 5

Wind Load Check and Glass Framing Deflection Limits

"Wind Load Check and Glass Framing Deflection Limits" is lesson 3 of 5 in the Glazing (C-17) Learning Hub. It opens with "What the Code Calls Vertical Glass" and works through 5 short steps, then a worked example you can check yourself against.

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Steps in this lesson

  1. What the Code Calls Vertical Glass
  2. Equation 24-1: The Wind Check
  3. Firmly Supported: The Edge Deflection Limit
  4. Interior Glazing Next to a Walking Surface
  5. When the Standard Rules Do Not Apply

The worked example in the course applies this lesson to a realistic job in 6 steps, from "Compare to the glass capacity" through "Check the long-edge rule for comparison".

What you'll be able to do

  • Explain the main idea of "Wind Load Check and Glass Framing Deflection Limits" in plain language you can use on the exam.
  • Apply this step with confidence: "Firmly Supported: The Edge Deflection Limit".
  • Apply this step with confidence: "Interior Glazing Next to a Walking Surface".
  • Apply this step with confidence: "When the Standard Rules Do Not Apply".
  • Test yourself on the worked example and the quick-check quiz inside the classroom.
Wind Load Check and Glass Framing LimitsWind Fgw = 28 psf6 ft x 9 ft lite(IG, glassedge = 9 ft)Mullion bows under load(exaggerated)L = 9 ft = 108 inWORKED EXAMPLE: 6 x 9 ft lite, 9 ft edges1. WIND CHECK (Eq 24-1): 0.6 Fgw ≤ FgaFgw = 28 psf (Sec 1609); Fga = 20 psf (E1300)0.6 x 28 = 16.8 psf ≤ 20 psf OK2. EDGE DEFLECTION LIMIT (CBC 2403.3)9 ft = 108 in, not over 13 ft 6 inlimit = L / 175 = 108 / 175 = 0.617 inframing calc 0.55 in ≤ 0.617 in OK3. IF THE EDGE WERE 15 ft (180 in):limit = L / 240 + 1/4 in= 0.75 + 0.25 = 1.00 inInterior glass by a walking surface: 2403.4(50 plf at 42 in; differential ≤ panel thickness)Glass passes the wind check; framing passes the L/175 limitEquation 24-1 uses 60 percent of Fgw; edge limit depends on edge lengthSource: 2025 California Building Code 2404.1 (Eq. 24-1), 2403.3, 2403.4CC
The diagram for this lesson, exactly as it appears in the Learning Hub.

The first steps of this lesson

Step 1: What the Code Calls Vertical Glass

CBC Section 2404.1 covers glass sloped 15 degrees or less from vertical: windows, curtain walls and window walls, doors, and other exterior applications. That glass must be designed to resist the wind loads from basic wind speed V in Section 1609 for components and cladding, and the load resistance of the glass under uniform load is determined in accordance with ASTM E1300. Glass in glazed curtain walls, storefronts, and partitions must also meet the seismic requirements of ASCE 7 Section 13.5.9.

Step 2: Equation 24-1: The Wind Check

The design of vertical glazing is based on Equation 24-1: 0.6 Fgw must be less than or equal to Fga. Fgw is the wind load on the glass from Section 1609, and Fga is the short-duration load the glass can carry as determined from ASTM E1300. Only 60 percent of the wind load is compared with the glass capacity. The glass supplier reads Fga from the E1300 chart for the exact thickness, type, and lite size, so the glazier should confirm that the lite delivered matches the shop-drawing size and thickness.

The remaining 3 steps, the worked example and the quiz are in the course. This is a preview. The full lesson, with the step-by-step explanations, a worked example and a quick-check quiz, is inside the classroom.

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