Tall wall mid height blocking.

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Author Message David G. Axt, CCS, CSI ,SCIP Senior Member Username: david_axt Post Number: 1367 Registered: 03-2002 Posted on Tuesday, July 22, 2014 - 01:40 pm:    My client is questioning the following information in my Section 061000 Rough Carpentry. "Provide continuous horizontal blocking at midheight of partitions more than 96 inches high, using members of 2-inch nominal thickness and of same width as wall or partitions." This language is straight out of MasterSpec. The architect said the structural engineer and contractor do not think that this blocking is necessary. The blocking will add cost to the project. I searched the IBC and could not find any information. It might be in NDS or ASCE 7 publication but I do not have them handy. Does anyone know where this requirement comes from? David G. Axt, CCS, CSI, SCIP Specifications Consultant/Web Publisher www.localproductreps.com Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 673 Registered: 10-2007 Posted on Tuesday, July 22, 2014 - 02:25 pm:    Blocking may be needed for fire blocking in the wall. The NDS does not appear to require this blocking. The structural engineer would be the one to evaluate the structural considerations. David G. Axt, CCS, CSI ,SCIP Senior Member Username: david_axt Post Number: 1368 Registered: 03-2002 Posted on Tuesday, July 22, 2014 - 02:44 pm:    Mark, Thank you for your response. I checked the 2012 IBC and could not find mid height wall requirements for either fire blocking or draft stopping. I am very puzzled on this blocking requirement. David G. Axt, CCS, CSI, SCIP Specifications Consultant/Web Publisher www.localproductreps.com Wayne Yancey Senior Member Username: wayne_yancey Post Number: 670 Registered: 01-2008 Posted on Tuesday, July 22, 2014 - 02:48 pm:    This blocking is also used to provide edge support for sheathing and gypsum board installed perpendicular to the framing. It will also help keep the studs straight and plumb. Ignore the last comment if the wall framing uses engineered lumber. Seems like a reasonable standard of care. Lynn Javoroski FCSI CCS LEEDŽ AP SCIP Affiliate Senior Member Username: lynn_javoroski Post Number: 1858 Registered: 07-2002 Posted on Tuesday, July 22, 2014 - 03:43 pm:    Agreed that this would be a standard of care; another "master spec" states this: "Provide framing and blocking members as indicated or as required to support finishes, fixtures, specialty items, and trim" as a general statement, and supplements that with language regarding specialty items, fireblocking, etc. It doesn't address wood framing, though, which is where this requirement is stated. It makes good sense, since more than 96 inches probably means substantially more height and the wallboard might be applied horizontally to maximize use and minimize waste. and you'd want the edge supported. It's almost a no-brainer. If the wall is 100 inches, maybe it's not needed; but I still want to be sure that edges of wallboard are supported. How many walls are over 96 inches? And how far over? Decide if it's worth the battle. Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1249 Registered: 03-2003 Posted on Tuesday, July 22, 2014 - 03:55 pm:    The only thing I could find is in Section 2308.9.9 (2012 IBC), which requires bridging when sheathing or wall coverings are not applied to both sides and the height-to-least-thickness ratio exceeds 50. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com spiper (Unregistered Guest) Unregistered guest Posted on Tuesday, July 22, 2014 - 05:28 pm:    I assume this is for wood stud partitions and not steel stud partitions (which I believe would not require the horizontal bridging, assuming the studs are the proper gauge, spacing, etc). Years ago when I worked construction over my summer breaks from school I was always told that this blocking was installed in taller walls to resist twisting of the wood studs. They were placed mid-span and not necessarily at potential gyp. bd. seams. It was typically installed in a staggered pattern so you could end nail them in place thru the 2x4s. In this fashion every other block is 1 1/2" off from the adjacent block so it would not provide edge support for horizontal gyp. board. I am not sure if the information I got was accurate but that is what I was told. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 674 Registered: 10-2007 Posted on Tuesday, July 22, 2014 - 08:07 pm:    Metal stud walls need bridging more than do wood walls. They just normally provide it in different ways. Justatim Senior Member Username: justatim Post Number: 60 Registered: 04-2010 Posted on Wednesday, July 23, 2014 - 07:17 am:    The traditional horizontal blocking, I understand was also an effort to have the whole wall work more as a membrane, so that localized loads/deformations, such as a heavy TV mount, will be distributed to more than one or two studs. You never know how an occupant will eventually use the wall. spiper (Unregistered Guest) Unregistered guest Posted on Wednesday, July 23, 2014 - 12:21 pm:    To expand on my first comment: I was always told that the blocking was installed to resist the twisting of the wood studs to avoid nail pops, cracked seams, etc. The contractor didn't initiate the blocking requirements but they provided it on taller walls because they felt that it helped save them the expense of call backs. We typically did it on walls over 10'-0" but I am not sure why it was decided that 10'-0" was the magic number. Back in the day we always nailed the gyp. bd. and nail pops where a big issue for the contractors. Screw attachment may have solved, or at least diminished, a lot of these problems. John Bunzick, CCS, CCCA, LEED AP Senior Member Username: bunzick Post Number: 1584 Registered: 03-2002 Posted on Wednesday, July 23, 2014 - 03:18 pm:    Yes, the blocking is both to resist twisting warp, and also to pull the studs into a more planar condition. Studs are not perfectly straight, so this helps make a better wall, aesthetically. Good carpenters will set studs with all natural cambers in one direction, but you can't count on that. In addition to all of that, it seems to me the blocking will also help strengthen the wall and help it resist flexure by transmitting forces to adjacent studs better than WB. Mark, I'm sure, will advise if I'm off-base on that. David G. Axt, CCS, CSI ,SCIP Senior Member Username: david_axt Post Number: 1369 Registered: 03-2002 Posted on Wednesday, July 23, 2014 - 07:47 pm:    Everyone brings up good point here! Thanks. Can anyone point me to a standard that dictates the mid-height blocking? David G. Axt, CCS, CSI, SCIP Specifications Consultant/Web Publisher www.localproductreps.com Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 675 Registered: 10-2007 Posted on Wednesday, July 23, 2014 - 08:40 pm:    I believe the 10'-0" requirement had to do with fire/draft stops. While blocking will help share load between studs I believe it is limited in how effective it is. I believe that plywood or OSB that is continuous over the stud is more effective in this regards. I do not believe that there is any standard requiring mid height blocking for 2x4 and 2x6 studs. My guess is that the 96" was introduced based on a perception of good practice. Since there is no documented basis available it makes it hard to change. In these situations individuals are putting forth a lot of guesses. This is why all sorts of weird requirements are in master specifications.