Q. On a recent project, we installed steel studs to the underside of the grid system for a suspended acoustical ceiling. I used screws to attach the runner track to the ceiling grid. I then installed my “kickers,” or permanent bracing to the structure above. I was then told to go back and remove all the temporary screws to allow the ceiling to float. Why?



A. The requirement for removing the temporary screws to hold the partition in place would depend on the Seismic Design Category assigned to the building by the architect and/or building department. This seismic rating system is new with the International Building Code and much more complicated than the old seismic zones of the past code. The old seismic zones (0-4) relied strictly on the project’s regional location.

The new SDC is a more complete analysis of the regional location, specific soil conditions, building occupancy and the maximum considered accelerated ground motion. The SDC ratings are Ratings A, B, C, D, E and F, with SDC A being the least seismic resistant and SDC F being the most seismic resistant. In suspended ceilings and partitions, there are three categories: A and B; C and D; and E and F.

If the ceiling was classified as a SDC C building, the answer would be that yes, the screws need to be removed. An SDC C ceiling is intended to be independent and free floating and cannot be tied to the partitions.

SDC designs D, E and F are intended and required to follow both the American Society of Civil Engineers 7-02 standard and the IBC. The ASCE 7-02 standard and the IBC section 1621.1.2 state that, “partitions that are tied to the ceiling and all partitions greater than 6 feet in height shall be independent of any splay bracing.” The intent by code officials is not to allow the use of the suspended grid system as bracing support for the partition.



EARTHQUAKE TESTED

The code authorities noted that after the Northridge and Nisqually earthquakes, non-load bearing partitions that relied solely on bracing from the grid system of a suspended lay-in ceiling did not hold up. Using the grid system to brace the partition is not allowed unless the grid system is specifically engineered to provide lateral support of the partition. The code clearly refers to the partitions that are “tied” to the ceiling. Removing the temporary screws is only required in buildings classified as an SDC C.

There is also the question of a seismic separation joint (if required) and code authorities are still struggling with this issue as it relates to section 1621.1.2. As always, each city may adopt and alter the code. Most major cities will amend, alter or make deletions to the code. I would suggest prior to installing the partitions, you ask the local building department if they use the IBC and/or have any special amendments or deletions to IBC 2003 section 1621.1.2