| Author |
Message |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 177
Registered: 08-2004
| | Posted on Thursday, April 10, 2008 - 12:11 pm: |    |
The Gypsum Assoc's recommendations for control joints refer to "partitions". Does anyone know if the same recommendations apply to INTERIOR CMU walls that are furred out w/gypsum board? |
Marc C Chavez
Senior Member
Username: mchavez
Post Number: 294
Registered: 07-2002
| | Posted on Thursday, April 10, 2008 - 12:43 pm: | |
not officially but wouldn't the furring essentially introduce the movement/expansion-contraction that the association was talking about anyway?
That being said I've seen many a wall that goes way beyond the requirements, with no cracks but then again my hind-end has not been on the line for it. |
Richard Howard, AIA CSI CCS LEED-AP
Senior Member
Username: rick_howard
Post Number: 168
Registered: 07-2003
| | Posted on Thursday, April 10, 2008 - 01:07 pm: | |
Joints in the furred gypsum should be at the same location as joints in the substrate. Control joints in masonry will be at closer spacing than needed for gypsum board, so that will determine the spacing. |
Robin E. Snyder
Senior Member
Username: robin
Post Number: 178
Registered: 08-2004
| | Posted on Thursday, April 10, 2008 - 01:39 pm: | |
Lets assume, for discussion purposes... that there aren't any movement joints in the CMU wall. |
Anonymous
| | Posted on Thursday, April 10, 2008 - 02:27 pm: | |
Then the CMU wall is only between 20 and 25 feet long. |
Richard Howard, AIA CSI CCS LEED-AP
Senior Member
Username: rick_howard
Post Number: 169
Registered: 07-2003
| | Posted on Thursday, April 10, 2008 - 03:41 pm: | |
Ah-ha! The difference between the theoretical and the practical.
I am on the third floor of a five-story spec office building. I can turn around in my chair and see a drywall partition that is about 65 feet long without a single control joint and there are no cracks either. However, if I walk around to the other side of the office, there is a wall that is 75 feet long and it has developed a nice straight vertical crack about 20 feet from one end.
What I don't know, is if the extra ten feet is the problem or if something else is going on behind the wall that is contributing to the crack. I suspect it is the latter.
Now, to answer your hypothetical question, I would be willing to take a chance with a large expanse of furred gypsum board over something substantial, such as CMU on a slab on grade, rather than drywall on steel studs on a suspended slab, which I know will deflect a whole lot more. If the joints in the panels had the stronger setting-type taping compound and all-purpose finishing compound, I would be even more comfortable. |
George A. Everding, AIA, CSI, CCS, CCCA
Senior Member
Username: geverding
Post Number: 417
Registered: 11-2004
| | Posted on Thursday, April 10, 2008 - 04:03 pm: | |
The age of the CMU also is important. Concrete masonry arrives on the jobsite as big and as wet as it will ever be, and continues to shrink as it cures. This drying shrinkage is independent of any temperature related shrinkage. You can expect about 1/2" of shrinkage in 100 feet of wall.
The 10 series NCMA TEK bulletins (10-1, 10-2, etc.) do a nice job of explaining. |
Wayne Yancey
Senior Member
Username: wayne_yancey
Post Number: 36
Registered: 01-2008
| | Posted on Thursday, April 10, 2008 - 04:13 pm: | |
If the gypsum board is installed over hat-shaped furring channels fastened to the CMU, place a control joint in the gyp board over the CJ in the CMU.
Recommend using 250S125-18 studs stud furring set in bottom and top tracks, no fastening to the CMU. 250S125-18 studs will permit install of junction boxes, something hat-channels will not do. |
Mark Gilligan SE, CSI
Senior Member
Username: mark_gilligan
Post Number: 49
Registered: 10-2007
| | Posted on Friday, April 11, 2008 - 01:43 am: | |
The key parameters are whether the CMU is grouted and reinforced and what are the joint spacings. If the block wall is grouted and reinforced there should be no need to joint the gypsum board except at joints in the wall.
In California where the practice is to fully grout the block and reinfore it with a moderate amount of horizontal reinforcing vertical joints are typically omitted with no problem. In this context CMU walls are similar to concrete walls.
The problems that lead to the recommendations for vertical joints were related to ungrouted and lightly reinforced or unreinforced walls. These tyes of walls essentially dont exist in California in new construction. |
4specs.com Home Page