allowable steel studs for UL assemblies

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Author Message Tony Wolf, AIA, CCS, LEED-AP Member Username: tony_wolf Post Number: 3 Registered: 11-2007 Posted on Thursday, September 04, 2008 - 02:20 pm:    In the July 2008 edition of Construction Specifier there is an ad for Dietrich Metal Framing which states “UltraSTEEL studs are the only UL Classified interior studs on the market today.” Is anyone changing specs in response to what seems could be a very large issue? Ralph Liebing, RA, CSI Senior Member Username: rliebing Post Number: 898 Registered: 02-2003 Posted on Thursday, September 04, 2008 - 02:29 pm:    As I recall the ad refers to just the V450 UL Assembly. Assume that is the tested panel run specifically with the Dietrich "UltraSTEEL" studs. That would make it parochial to just that system I'm sure there are many other UL approved tests using other steel studs. Tony Wolf, AIA, CCS, LEED-AP Intermediate Member Username: tony_wolf Post Number: 4 Registered: 11-2007 Posted on Thursday, September 04, 2008 - 02:38 pm:    No. Based on a Dietrich presentation that detailed the requirements of all the rated designs, most were run decades ago, with slightly larger flange and flange return dimensions. Technically, they are correct, on the order of 1/8 and 1/16 inches. Tony Wolf, AIA, CCS, LEED-AP Advanced Member Username: tony_wolf Post Number: 5 Registered: 11-2007 Posted on Thursday, September 04, 2008 - 03:03 pm:    If anyone is interested, I'll email a pdf of the ad and Dietrich's analysis. first.lastATsmithgroup Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 667 Registered: 03-2003 Posted on Thursday, September 04, 2008 - 04:58 pm:    Here's my take: Dietrich had to get their own assembly tested because their product could not qualify as a metal stud under the generic requirements for metal studs in many of the UL assemblies. Most UL assemblies state the minimum thickness or MSG (manufacturer's standard gage). But UltraSteel touts that their products are equivalent to standard gages, but using a thinner metal. Therefore, being a very proprietary product, they had to go out and conduct testing specifically for their product so it could be used in fire-resistance-rated assemblies. Using another metal stud manufacturer's product in a fire-resistance-rated wall doesn't mean it will fail--as long as the stud meets the minimum requirements of the assembly. The problem with UL Assembly V450 is that the UltraSteel stud can only be used in that condition (with the exception of optional insulation and resilient channels), whereas a standard steel stud can be used in many different assemblies in the UL Directory. Steven Bruneel, AIA, CSI-CDT, LEED-AP Senior Member Username: redseca2 Post Number: 130 Registered: 12-2006 Posted on Thursday, September 04, 2008 - 05:53 pm:    This reminds me of a discussion we had in our firm some years ago with a representative for a major manufacturer of gypsum board products. They pointed out that while they had tested their type "X" products in every conceiveable UL assembly in both vertical and horizontal applications of the board, some of their competitors had only tested with the gypsum board installed vertically. So if you were in a situation where the code enforcement authorities acted as if "extremism in building code enforcement is no vice", like our Hospital projects almost always are, you might find your project in a bit of difficulty if you were not clear in your documents how it should be installed. I know that we often specify an impact resistant gypsum board for the lower portion of corridor walls and (until that moment) assumed they would lay it up long side down. Tony Wolf, AIA, CCS, LEED-AP Senior Member Username: tony_wolf Post Number: 6 Registered: 11-2007 Posted on Friday, September 05, 2008 - 09:17 am:    Ron, I think you're right about Dietrich needing to get their own test. But their argument is that the commercially available metal studs today do not meet the studs described in almost all the other UL assemblies, due to one or more of the following: flange width, flange return dimension, or metal thickness. The flyer they've published lists all 1- and 2-hour UL assemblies and the reason current metal studs do not comply. I resist the restraint on competition that is implied, but the potential liability problems suggest a new spec requirement specifically addressing stud conformance to UL assembly requirements. The reason I've brought this up: This seems like a potentially explosive situation, but I find no one [except in my firm] who is concerned. Anonymous   Posted on Friday, September 05, 2008 - 10:18 am:    Isn't it reasonable to rely on the use of established standards and tests-- vis-a-vis UL-- and if there is a liability problem, due standard of care would support that. Violation of a UL design then becomes the manufacturer's liability; and perhaps UL's for non-enforcement. I share Ron's concern over the proprietary product issue, and find it a little hard to then rely on a competing manufacturer's research and "standard" that finds its product to be the sole solution. Dietrich is a good reliable firm, but still, business-edge is still business-edge. Richard Howard, AIA CSI CCS LEED-AP Senior Member Username: rick_howard Post Number: 192 Registered: 07-2003 Posted on Friday, September 05, 2008 - 10:50 am:    Both Dietrich and Clark-Western provide studs using UltraSteel licensed material and have shared the testing to get the UL listing. They also have a joint marketing effort to inform us designers of the code problems with current non-UltraSteel studs, mostly the 25-gage products. The bizarre thing about this is that lighter metal studs of a given section modulus can more easily pass UL testing because the rate of heat transfer through the assembly is not as fast as studs of beefier stature. It may be that the current stud products can meet the UL tests by engineering analysis. If that is the case, manufacturers would be able to produce a letter of equivalence from UL for their products. If they can't, then perhaps it is time to get the appropriate testing done with the current products. Jerry Tims Senior Member Username: jtims Post Number: 29 Registered: 04-2005 Posted on Friday, September 05, 2008 - 10:56 am:    According to a Dietrich rep who put on a product luncheon in our office a few months ago, Clark-Western actually purchases their studs from Dietrich. However, I can't say whether this is indeed fact or fiction. Tony Wolf, AIA, CCS, LEED-AP Senior Member Username: tony_wolf Post Number: 7 Registered: 11-2007 Posted on Friday, September 05, 2008 - 11:17 am:    My understanding from Dietrich's rep is that they licensed C-W to produce their own studs. In any case, it remains to be proven whether this will generate competition. I'm not sure who would request the UL engineering studies. Perhaps we need to press the gypsum board manufacturers, who sponsored the tests, to have the engineering studies done. I find another bizarre thing about this: Ingenuity has taken what is arguably the flimsiest part of current construction and made it yet flimsier, Dietrich's tests notwithstanding. Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 668 Registered: 03-2003 Posted on Friday, September 05, 2008 - 11:18 am:    The UltraSteel is a Dietrich product which licenses it to other manufacturers since it is a patented design. Clark-Western is apparently the only company to take them up on the offer, so far. Richard Howard, AIA CSI CCS LEED-AP Senior Member Username: rick_howard Post Number: 193 Registered: 07-2003 Posted on Friday, September 05, 2008 - 11:36 am:    Has anyone tried going for a LEED ID point by claiming a 20 percent reduction in steel by using these studs? Colin Gilboy Senior Member Username: colin Post Number: 148 Registered: 09-2005 Posted on Friday, September 05, 2008 - 11:41 am:    Ultrasteel is actually a British product licensed by both Dietrich and ClarkWestern. I asked ClarkWestern about this when they added the word to their ad on 4specs. http://www.hadleygroup.co.uk/Products/UltraSTEEL/tabid/390/Default.aspx Mark Gilligan SE, CSI Senior Member Username: mark_gilligan Post Number: 83 Registered: 10-2007 Posted on Friday, September 05, 2008 - 11:41 am:    The UltraSTEEL product achieves added capacity by embossing the metal and may be a reasonable product for certain applications. This product should NOT be seen as a direct replacement for all metal stud uses. I would see it as limited to interior non-bearing partitions. It cannot have the same section modulas or moment of inertia as a stud with thicker material. The capacity of screw attachments will be less given the thinner material. The thinner material would also mean that it would have a shorter service life in corrosive environments. Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 669 Registered: 03-2003 Posted on Friday, September 05, 2008 - 12:04 pm:    I did a little checking (not a thorough research by any means) and found some manufacturers do not meet some of the UL assemblies involving C-shape studs; but many do comply with several of the assemblies in the UL Directory. Almost all of the manufacturers I checked provide studs in the widths, flange widths, and MSG/thicknesses that are indicated in the assemblies I checked. As for differences, it is in the flange return dimension that I found to be inconsistent. Typically, when indicated in a UL assembly, the flange width is 1/4-inch. Manufacturers that I've checked have 13/64-inch, 0.188-inch, 1/2-inch, and some didn't indicate a dimension at all. However, many assemblies indicate the MSG/thickness, width, and compliance with the American Iron and Steel Instute's (AISI) specifications for cold-formed steel members. The Steel Stud Manufacturers' Association (SSMA) information states that their members' products comply with AISI specifications. Therefore, studs manufactured by SSMA members and complying with the given dimensions (MSG/thickness and width only) per the UL assembly are acceptable. Another thing to keep in mind is that UL is not the only source for fire-resistance-rated construction. The IBC includes many generic assemblies in Table 702.1(2), and it isn't specific on flange or flange return dimensions. Additionally, in Footnote "o" of Table 720.1(2), it states that the generic assemblies in GA-600 are also permitted; and they aren't specific in flange or flange return dimensions, either. In my opinion, there are no code problems with "non-UltraSteel" studs. Ronald L. Geren, AIA, CSI, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 670 Registered: 03-2003 Posted on Friday, September 05, 2008 - 12:13 pm:    Colin, thanks for correcting me (us). Apparently I received some bad info from the Dietrich rep at the 2006 CSI Show. Mark, you bring up some good points. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 95 Registered: 01-2008 Posted on Friday, September 05, 2008 - 01:22 pm:    Dimpling the flanges of steel studs is not new. Up to and including the 1980s interior light gage, nonloadbearing studs were dimpled (not to the extent of UltraSteel) to catch the screws to prevent the screws from walking. Over time manufacturer's eliminated the dimples. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 950 Registered: 03-2002 Posted on Friday, September 05, 2008 - 02:25 pm:    Mark: Dietrich's website claims that they have tested screw retention, and that it is higher than with standard studs. They say this is because the shape of the dimples engages more threads than with the flat sheet of standard studs. http://www.dietrichmetalframing.com/ultrasteel/benefits.asp Also, their website, and their ES Evaluation report, state specifically that they are approved for interior non-load bearing walls. No mention of load-bearing assemblies or exterior use. Mark Gilligan SE, CSI Senior Member Username: mark_gilligan Post Number: 84 Registered: 10-2007 Posted on Saturday, September 06, 2008 - 12:29 pm:    I believe that Dietrich's literature emphasizes those characteristics that make their product look good and does not expend the same effort on those aspects where their product doesn't shine. The emphasis in the link is on pull-out capacity of the screw. In other situations we are more concerned about the shear capacity which will be limited by the side of the screw pushing against the edge of the sheet. Dimpling would not improve this limit state and might actually result in a lower cpacity. This is likely not a problem for your typical interior partition but there are situations where this could be a concern. This is a classic case where we need to learn to get beyond the hype of a new product. It also appears that this marketing literature is aimed to architects and contrctors who do not necessarily have the background to identify the limitations of the claims. I also believe that some sub-contractors are substituting Ultrsteel studs for conventional studs in load bearing situations without asking permission.