Astm C920 Class 25 Vs Class 50 [new] May 2026

“What’s the spec?” Marcus asked, pulling his collar against a sudden gust.

Marcus closed his eyes. This was the ancient conflict: astm c920 class 25 vs class 50

Pat laughed. “Because I don’t trust the installation crew to keep the joint width perfect. Class 50 forgives a ½-inch joint that’s actually ⅝ inch. Class 25 demands precision. Also—check the building’s wind-sway calculation. At the 30th floor, the deflection is 2 inches. That joint is moving ±45% on the corners. Class 25 would be at 180% of its limit. It’s not a matter of if it fails—it’s when .” “What’s the spec

The Sealant That Saved the Tower

“Exactly,” Sam said. “Class 25 is for moderate climates, interior joints, or spandrel glass. Class 50 is for abuse —high rises, bridges, parking decks, anything that twists in the wind. The engineer spec’d Class 50 for a reason.” “Because I don’t trust the installation crew to