Supporters of an updated structural building-design standard, developed by the American Society of Civil Engineers, are breathing a collective sigh of relief after members of the International Code Council voted down an attempt to keep the standard, known as ASCE 7-16, out of the 2018 edition of ICC’s International Building Code and its other model codes.
But any victory celebration is premature. The 65-40 floor vote on Oct. 19 at an ICC meeting in Kansas City, Mo., was advisory only. It has no teeth.
Still to come is the binding online ballot—tentatively scheduled for Nov. 8 to Nov. 21—for or against an all-or- nothing replacement of ASCE 7-10. ICC expects to release unofficial ballot results in early December.
“Failure of the ICC to adopt ASCE 7-16 would be a major missed opportunity for the U.S. to improve the way buildings are designed and constructed,” says Ronald O. Hamburger, chairman of ASCE 7’s main committee and a senior principal with Simpson Gumpertz & Heger Inc.
The National Association of Home Builders (NAHB) opposes the ICC adoption of SEI ASCE 7-16: “Minimum Design Loads for Buildings and Other Structures” because of new provisions relating to seismic loads; tsunami-resistant design for critical buildings for the West Coast, Alaska and Hawaii (ENR 10/10 p. 8); and, especially, increases in low and flat roof wind-pressure coefficients—mostly along a 600-ft strip for about 1,000 miles on the southeastern seaboard and Gulf Coast.
“ASCE 7-16 contains numerous technical changes that will significantly affect the design and increase the cost of construction of one- and two-family dwellings and low-rise multifamily residential buildings,” says NAHB in its written comment submitted to ICC.
“The roofing issue has probably raised the most controversy across the industry,” says Gary Ehrlich, NAHB’s senior program manager for structural codes and standards and a member of the ASCE 7 main committee and two subcommittees.
On affected buildings, the new wind provisions would require more fasteners at edges and corners, where pressure increases are the greatest, says Ehrlich, who spoke “reluctantly in opposition” to the update at ICC’s 2016 Annual Conference, Public Comment Hearings & Expo, held Oct. 16-25. The associated cost premium is difficult to pin down because it depends on the exposure, slope and framing of a specific building. But Ehrlich estimates, for a low-rise building with a 40-ft x 60-ft footprint, the extra cost could be $5,000.
Jason Wilen, director of technical services for the National Roofing Contractors Association, also spoke in opposition to the update, saying there are “no real-world failures” to justify increased design wind pressures. “We cannot support the change going forward,” said Wilen.
“The roofing issue has probably raised the most controversy across the industry.”
— Gary Ehrlich,
National Association of Home Builders
Also at the hearing, a dissenting consulting engineer said the changed wind provisions would be problematic, add complexity, and increase the chances of mistakes in design and construction.
In response, Hamburger said that, compared to ASCE 7-10, the 2016 standard has generally reduced wind speeds—and design loads—across the U.S. In Portland, Ore., for example, the reduction in wind force is 30%; in Dallas, 20%; and in Chicago, 15%, according to Hamburger.
Beyond wind, NAHB is concerned about some tightened seismic provisions. Changes in site classification factors and increases in the spectral accelerations for portions of South Carolina, Tennessee, New Hampshire and other areas of the nation could increase the cost of a house by about $6,000, said Ehrlich.
Jon Siu, principal engineer in Seattle’s Dept. of Construction and Inspections, spoke in support of change. “We are continuously learning, particularly about seismic,” he said. “If we don’t update, we are going to lose helpful provisions.”
Steven Winkle, who represented the American Institute of Architects, said the changes from ASCE 7-10 are contemporary, coordinated and comprehensive. “Wind reductions and increases are all empirically based,” he said.
Regarding ASCE 7-16’s tsunami- resistant-design provisions, NAHB is concerned about local jurisdictions extending the requirements from critical to light-frame construction, forcing a switch to more-costly concrete or steel framing.
Supporters of ASCE 7-16 also are frustrated by the ICC voting process—both the advisory vote at the hearing and the online vote, in effect since 2014—designed to allow members to vote who aren’t at hearings. In the end, “it comes down to a series of highly technical, two-minute statements and one-minute rebuttals about some very particular changes,” says John D. Hooper, a member of the ASCE 7-16 main committee and a senior principal of Magnusson Klemencic Associates. “It makes it very difficult on those voting to really understand the depth of the issues.”
ASCE 7-16 represents the work of more than 300 volunteers over five years. The standard’s proponents are also unhappy that the upcoming vote is to replace all of ASCE 7-10 or none of it. They maintain that, if successful, the challenge to the update also would reject important new guidance in the standard that is not controversial.
An example is detailed ground snow-load data for 352 cities in eight states. “The tables of ground snow loads make the data on design snow loads easier to find and more uniform,” says Hamburger.
At the hearing, he pleaded with the ICC voting members, saying, “Don’t throw the baby out with the bathwater.”