Structural Code Committee Votes to Amend Deflection Limits for Aluminum Used in Skylights and Sunrooms

Daniel J. Walker, M.E., of Thomas Associates Inc., representing the National Sunroom Association, went before the Structural Code Committee yesterday to propose that footnotes "h" of the International Building Code's Table 1604.3 and "c" of R301.7 have the following text added: For continuous aluminum structural members supporting edge of glass, the total load deflection shall not exceed L/175 for each glass lite or L/60 for the entire length of the member, whichever is more stringent.

The proposal was approved by a vote of 13-0.

Footnote "h" of Table 1604.3 will now read: For aluminum structural members or aluminum panels used in skylights and sloped glazing framing, roofs or walls of sunroom additions or patio covers, not supporting edge of glass or aluminum sandwich panels, the total load deflection shall not exceed L/60. For continuous aluminum structural members supporting edge of glass, the total load deflection shall not exceed l/175 for each glass lite or L/60 for the entire length of the member, whichever is more stringent. For aluminum sandwich panels used in roofs or walls of sunroom additions or patio covers, the total load deflection shall not exceed L/120.

Footnote "c" of Table R301.7 will now read: For aluminum structural members or panels used in roofs or walls of sunroom covers, not supporting edge of glass or sandwich panels, the total load deflection additions or patio shall not exceed L/60. For continuous aluminum structural members supporting edge of glass, the total load deflection shall not exceed L/175 for each glass lite or L/60 for the entire length of the member, whichever is more stringent. For sandwich panels used in roofs or walls of sunroom additions or patio covers, the total load deflection shall not exceed L/120.

Mike Fischer, code consultant for the Window and Door Manufacturers Association and an original author of the footnote, spoke in favor of the addition.

"We didn't tell the code officials [in the original footnote] what the deflection limit should be," he said. "This language is much better worded."

He added, "For this application, it needs to be L/175."

Questioned by several members of the committee as to where the L/175 figure came from, Fischer advised it's the figure used in ASTM E1300 as the requirement for strength testing.

Kirk Grundahl, PE, president of Qualtim Inc. in Madison, Wis., motioned to approve the proposal.

"It provides clarity," he said, prior to the 13-0 vote in favor of the proposal.

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