bracing for non-load bearing partitions

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Author Message Robin E. Snyder Senior Member Username: robin Post Number: 104 Registered: 08-2004 Posted on Thursday, April 19, 2007 - 02:00 pm:    Who typically designs the bracing for interior non-load bearing partitions? Wayne Yancey Senior Member Username: wyancey Post Number: 352 Registered: 05-2005 Posted on Thursday, April 19, 2007 - 02:41 pm:    Designer of record unless you transfer (foist) that responsibility to the supplier but I think that is the easy way out. I take ownership of specifying gauge and spacing based on partition height and eventual surface finish (deflection limitations) and apply quidelines from SSMA or GA for bracing. It is a combination of words and pictures (specs and drawings). Robin E. Snyder Senior Member Username: robin Post Number: 105 Registered: 08-2004 Posted on Thursday, April 19, 2007 - 03:26 pm:    Wayne: Do you have any verbage for your specs that helps cover it? Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 528 Registered: 07-2002 Posted on Thursday, April 19, 2007 - 03:52 pm:    in my office now (and my previous office) we required it to be contractor designed. On the west coast, that work is often engineered by the structural engineer for the seismic requirements; however on the east coast, the structral engineers don't even think of doing that. I see it as our responsibility to provide the required design loads and then we ask for structural calculations from the supplier/subcontractor. Robin E. Snyder Senior Member Username: robin Post Number: 106 Registered: 08-2004 Posted on Thursday, April 19, 2007 - 04:24 pm:    I found this reference: Bracing shall conform to Section D3 of the AISI Specifications. But, can't seem to location the "AISI Specifications" much less D3. Anyone know what it says? Wayne Yancey Senior Member Username: wyancey Post Number: 354 Registered: 05-2005 Posted on Thursday, April 19, 2007 - 05:21 pm:    For axial and windload bearing light metal framing, I agree with Anne and I write a performance specification but, in my humble opnion, for interior nonload bearing steel stud partitions it is the designer of record's responsibility based in 5 psf and deflection limits of 1/120 or 1/180 or 1/240 or 1/360. Deflection limits and height based on partition height and face finish (such as ceramic wall tile). Refer to Tile Council of North America for recommended stud depths, gauge, and spacing for ceramic tile. Refer to the SSMA ICBO ER-4943-P for limiting height wall table - composite. David R. Combs, CSI, CCS, CCCA Senior Member Username: davidcombs Post Number: 226 Registered: 08-2004 Posted on Thursday, April 19, 2007 - 06:15 pm:    We leave it to the contractor (via delegated design performance spec). A few things to consider: • Stud manufacturers typically publish span tables for their products, based on the loads and deflection criteria Wayne mentions above, stud size, stud spacing, stud gage, and stud flange width. I have not really found two manufacturers' tables to be identical. • We really do not know which stud manufacturer the contractor will be using, until we get the submittal. • There are several ways to stiffen a partition so that it does not exceed the span criteria: 1) Increase stud depth, 2) Increase stud gage, 3) decrease stud spacing, and 4) install diagonal bracing above ceiling. • Depending on actual field conditions and interferences, some of these methods may work better than others, or may be able to work in combination. It is not always easy, during design and construction documents, to ascertain which method(s) are appropriate or cost effective for the contractor to implement under all the potential circumstances. There are too many variables, and our crystal ball just isn't that shiney. For our projects, the contractor is given the choice / option to use any or all of the above methods, and the flexibility to choose based on actual field conditions encountered. Bottom line: The published span limitations are not be exceeded, and the stiffening methodology ultimately chosen is at no additional cost to the Owner. Gerard Sanchis (Unregistered Guest) Unregistered guest Posted on Thursday, April 19, 2007 - 07:17 pm:    I'd be careful about loads. 5 psf may be okay for most interior partitions, but we specify 10 psf for air shafts and 15 psf for lobbies in certain areas. For high speed elevator shafts the loads may be higher. As for bracing, in addition to the above, horizontal channels at +48 inches o.c. also works. Wayne Yancey Senior Member Username: wyancey Post Number: 355 Registered: 05-2005 Posted on Thursday, April 19, 2007 - 07:57 pm:    Gerald is right on regarding the loading. 5 psf is the starting point as required by code but will increase for shafts that serves as R/A plenums, elevator shafts. Also influencing is height of building, speed of elevators to accommodate tall buildings, etc, and the beat goes on. With respect to span tables, I rely on the published tables on products from members of the Steel Stud Manufacturers Association (SSMA) and the Universal Designator System for light gage steel framing (loadbearing and nonloadbearing). Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 529 Registered: 07-2002 Posted on Thursday, April 19, 2007 - 08:17 pm:    keep in mind also that those walls may have to support wall mounted counters and shelving that could increase the loads substantially. we do give them the loading requirements in those instances, but for the same reasons that David mentions, we have no control over which steel gets used by the selected subcontractor. some of the design options are effective on each job, and some are totally inadequate. John Bunzick, CCS, CCCA Senior Member Username: bunzick Post Number: 704 Registered: 03-2002 Posted on Friday, April 20, 2007 - 09:59 am:    I looked at this recently. The "maximum stud height" table in ASTM C754 "Installation of Steel Framing Members to Receive Screw-Attached Gypsum Panel Products" shows that for 5 PSF loading, L/240 deflection, 16 inch o.c. spacing, 0.0179 in (26 ga), and 3-1/2 inch depth, the maximum partition height is 15'-4". Since this is a much greater height than we typically have (and a thinner gauge,) I decided not to worry about it. Instead, I would keep my eye out for conditions that exceed this where another partition type, or special language, would be used. However, I do have concerns about wide openings in these partitions where the deflection would be adversely affected, and for "suspended" walls (not supported on the floor). These are conditions I think need to be engineered, and we have assigned that to the contractor. Mark Gilligan SE, CSI Senior Member Username: markgilligan Post Number: 161 Registered: 05-2005 Posted on Friday, April 20, 2007 - 11:14 am:    Regards the question as to who is responsible to bracing interior partitions. It is the Prime Design Professionals, unless excluded from their contract, to either define it themselves, hire a consultant, or to deal with the obligation by delegating it to the Contractor. Some architects have been successful in dealing with most cases trough the use of typical details developed in cooperation with an engineer. The arguments that the differences in stud manufactures products necessitates delegating the design is no longer a real issue. The Steel Stud Manufacturers Association (SSMA) have agreed upon a standard notation system and agreed minimum properties (ref www.ssma.org) thus allowing you to define the sizes and benefit from multiple manufacturers bidding. In fact for generic stud and track sizes it is no longer necessary to list manufacturers in the specifications instead you specify compliance with the ICBO evaluation report. When delegating the design of a system care should be given to understanding and defining the limits on the contractor. All too often people think delegated design and then turn off the brain which can lead to problems. If you delegate design of interior partitions you need to define the thickness of the wall, design loads including forces from cabinets and equipment, deflection criteria, whether the walls go full height or stop at the ceiling, the need to accommodate other building systems, etc etc. If you are attaching a lot of items to the partitions you may want to specify minimum thickness of material... It is my opinion that delegated design works best when you do not have any other loads on the wall, have only small openings, your expectations are low, and you are in low seismic region. One advantage to delegating the design is that the engineering costs do not come out of the fees paid the Architect. On hospital and public school projects in California you do not even think about delegating the design both because the plan checkers will not accept this option and because of the seismic loads from cabinets, and equipment drive the design. Note that sometimes the seismic design loads may be larger than 5psf. David R. Combs, CSI, CCS, CCCA Senior Member Username: davidcombs Post Number: 227 Registered: 08-2004 Posted on Friday, April 20, 2007 - 11:20 am:    It is also worth mentioning that, according to the TCNA Handbook, for many of their wall tile installation methods (for those applied to metal stud partitions), they recommend minumum 20 gage studs, minimum 3 5/8" deep, maximum spacing of 16" o.c. - irrespective of the partition height. This goes back to what Anne said: It's not just the partition, but what is hanging from, or attached to it.