Palm Beach County Contractors

The Frame Behind Glass

Curtain wall mullions bend under wind pressure. Watch the deflection in real-time and learn why L/175 vs L/240 matters for keeping glass intact during Palm Beach hurricanes.

Calculate Wind Loads Deflection Calculator
0.0" GLASS CONTACT! MULLION SPAN: 10 ft L/175 0.69" PRESSURE -65 psf

Deflection Limits Explained

The "L" in L/175 is the span length. Divide by the number to get max deflection.

L/175 Standard

Most Common
  • 10 ft span = 0.69" max deflection
  • Standard for most curtain wall systems
  • Adequate glass edge clearance for standard glazing
  • May be tight for large panels in high wind zones

L/240 Premium

High Performance
  • 10 ft span = 0.50" max deflection
  • Better glass edge clearance margin
  • Recommended for hurricane zones
  • Less noticeable deflection during storms

Deflection Calculator

Find maximum allowed deflection for your mullion span.

Mullion Deflection Calculator
Mullion Span 10 ft
Deflection Limit L/175
Max Deflection
0.69"
Edge Clearance Needed
3/8"
Safety Factor
1.5x

Common Questions

Most curtain wall specs require L/175 deflection limit, meaning the mullion can deflect 1/175 of its span under design wind load. Some high-end projects specify L/240. In Palm Beach County with 170 mph winds, tighter deflection limits may be needed to prevent glass edge contact.
Glass panels sit in the mullion pocket with a small edge clearance - typically 1/4 inch. If the mullion deflects too much, it can contact the glass edge and cause stress cracks or breakage. Proper deflection limits keep glass safe during wind events.
Deflection = (5 * w * L^4) / (384 * E * I), where w is the wind load per foot, L is the span, E is the modulus of elasticity, and I is the moment of inertia. For a 10-foot mullion at L/175, maximum deflection would be 10*12/175 = 0.69 inches.
Mullion Design
Span 10 ft
Limit L/175
Max Deflection 0.69"