By Terry Kastner, Executive Director | Northwest Wall and Ceiling Bureau
It seems that many of us would prefer to use the Composite Wall Heights Tables rather than the Non-Composite Wall Heights Tables when selecting our framing members. Typically, the framing members shown in the Composite wall table can achieve greater limiting wall heights than the Non-Composite Tables. That may seem fine, but we should understand exactly what a Composite Wall is and how it must be constructed before we use those tables.
All of the cold-formed metal manufacturers have similar charts and tables that provide the performance capabilities of their framing members, and all of the CFM manufacturers’ catalogs provide a Composite and Non-Composite Wall tables for determining the Limiting Height for each stud size.
We generally believe that a composite wall has drywall that extends full height on both sides of the wall and a non-composite wall may not.
All of the CFM Manufacturers have a note similar to the Composite Assemblies below.
COMPOSITE ASSEMBLIES:
Use Composite limiting height data when walls are sheeted with gypsum board on both flanges of the stud for the full height of the wall. Composite limiting height data meets 2012 and 2015 IBC's and was tested and analyzed using the most recent version of AC86.
Composite Wall Limiting Heights:
Table Notes
AND/OR
The problem with the Composite Tables is that as long as the CFM Manufacturers Framing System catalogs and their third party ES Report states that the heights were determined using ICC-ES AC-86, the wall must be constructed with the gypsum board installed in the vertical orientation, without any seams, and the gypsum board must be fastened around the entire perimeter including the head track, regardless of the type of top track. “Seamless” means that the wall must be no taller than the longest available panel of gypsum board. Again, this is the same for all manufacturers, and the composite language for all is the same.
If your wall can be constructed with gypsum board installed the full height of the partition, in the vertical orientation, to both sides of the partitions, screw-fastened around the entire perimeter of the gypsum panels, including the top track, then you can use the composite wall tables to determine the proper stud. But, if you cannot install the gypsum panels in the vertical orientation, or you cannot screw the gypsum panel to the top track, or the height of the partition necessitates stacking gypsum panels, then you do not have a composite wall and should use the Non-Composite Wall Tables.
For example, if you have a wall that is 14’6” in height and you want to use a 3-5/8 stud, 24” o.c. with a L240 and 5psf, the Composite Wall table states that you can use a nonspecific 362 33EQD type stud which will achieve a 14’10” height. But, because the standard maximum length of gypsum panels is 12’, you cannot create a composite wall because you will have a joint or seam at 12’. So, you have a non-composite wall. If you go to the non-composite wall for the same stud, you may see that the limiting height maximum for that stud in the Non-Composite Table is only 12’11”, not 14’10”.
The inspector, seeing that the stud you are using is not appropriate for the height of the wall, would/could make you install the studs 16” o.c., which would achieve a 14’9” limiting height, rather than your planned 24” o.c. Or, if you had already framed and rocked the walls before the inspector realized that the studs or spacing was undersized, I am not sure what an inspector from any municipality would require, but it would at least be to have the walls engineered to see if the if the stud you used can meet the height requirement. In this case, you had better go back to the CFM manufacturer’s engineer to see if they can help you. Good luck!
So, I would advise all of our contractors to be aware of the requirements when using the Composite Wall Tables, take the proper and conservative approach and use the Non-Composite Limiting Wall Heights Table. Or, if you are going to use the Composite Table, call an engineer for the manufacturer to ensure that the stud you are planning to use is appropriate for the conditions.
All of the cold-formed metal manufacturers have similar charts and tables that provide the performance capabilities of their framing members, and all of the CFM manufacturers’ catalogs provide a Composite and Non-Composite Wall tables for determining the Limiting Height for each stud size.
We generally believe that a composite wall has drywall that extends full height on both sides of the wall and a non-composite wall may not.
All of the CFM Manufacturers have a note similar to the Composite Assemblies below.
COMPOSITE ASSEMBLIES:
Use Composite limiting height data when walls are sheeted with gypsum board on both flanges of the stud for the full height of the wall. Composite limiting height data meets 2012 and 2015 IBC's and was tested and analyzed using the most recent version of AC86.
Composite Wall Limiting Heights:
Table Notes
- Allowable composite limiting heights are calculated using ICC-ES AC86-2012.
- No fasteners are required for attaching the stud to the track.
- Stud end bearing must be a minimum of 1 inch.
- Composite limiting heights are based on a single layer of 5/8" type X gypsum board installed in the vertical orientation to both sides of the wall over full height using minimum No. 6 Type S Drywall screws spaced a maximum of 12" oc for studs at 24" spacing, and 16" oc for studs at 16" and 12" spacing.
AND/OR
- Allowable composite limiting heights are calculated using ICC-ES AC86-2010. The ¹/3 stress increase for strength was not used.
- The gypsum board must be applied full height in the vertical orientation to each stud flange and installed using minimum #6 Type S drywall screws, per ICC-ESR2507 Section 4.2. and per IAPMO-UER 0313.
- No fasteners are required for attaching the stud to the track.
- Stud and bearing must be a minimum of 1".
- Galvanizing to be G40 minimum for 10 PSF or less, and G60 minimum for greater than 10 PSF lateral loads.
The problem with the Composite Tables is that as long as the CFM Manufacturers Framing System catalogs and their third party ES Report states that the heights were determined using ICC-ES AC-86, the wall must be constructed with the gypsum board installed in the vertical orientation, without any seams, and the gypsum board must be fastened around the entire perimeter including the head track, regardless of the type of top track. “Seamless” means that the wall must be no taller than the longest available panel of gypsum board. Again, this is the same for all manufacturers, and the composite language for all is the same.
If your wall can be constructed with gypsum board installed the full height of the partition, in the vertical orientation, to both sides of the partitions, screw-fastened around the entire perimeter of the gypsum panels, including the top track, then you can use the composite wall tables to determine the proper stud. But, if you cannot install the gypsum panels in the vertical orientation, or you cannot screw the gypsum panel to the top track, or the height of the partition necessitates stacking gypsum panels, then you do not have a composite wall and should use the Non-Composite Wall Tables.
For example, if you have a wall that is 14’6” in height and you want to use a 3-5/8 stud, 24” o.c. with a L240 and 5psf, the Composite Wall table states that you can use a nonspecific 362 33EQD type stud which will achieve a 14’10” height. But, because the standard maximum length of gypsum panels is 12’, you cannot create a composite wall because you will have a joint or seam at 12’. So, you have a non-composite wall. If you go to the non-composite wall for the same stud, you may see that the limiting height maximum for that stud in the Non-Composite Table is only 12’11”, not 14’10”.
The inspector, seeing that the stud you are using is not appropriate for the height of the wall, would/could make you install the studs 16” o.c., which would achieve a 14’9” limiting height, rather than your planned 24” o.c. Or, if you had already framed and rocked the walls before the inspector realized that the studs or spacing was undersized, I am not sure what an inspector from any municipality would require, but it would at least be to have the walls engineered to see if the if the stud you used can meet the height requirement. In this case, you had better go back to the CFM manufacturer’s engineer to see if they can help you. Good luck!
So, I would advise all of our contractors to be aware of the requirements when using the Composite Wall Tables, take the proper and conservative approach and use the Non-Composite Limiting Wall Heights Table. Or, if you are going to use the Composite Table, call an engineer for the manufacturer to ensure that the stud you are planning to use is appropriate for the conditions.
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