Q: Can you explain the term “spot-grouting” in the installation of steel door frames in commercial applications?
A: Spot-grouting in cold-formed steel framing and gypsum panel systems relates to the interface between the door frame and an interior partition system. Spot-grouting can be considered archaic—the practice is not used anymore. The intent was to keep the door frame from twisting during the normal operation of the door. The practice has its roots dating back to conventional gypsum plaster systems where the recommendation was to fully grout the door frame with plaster to stiffen the frame. In steel frame gypsum panel systems, it was sometimes specified to fully grout the frames, but in these cases, it was for acoustical reasons.
In fully grouting the frame, a plaster-like material was used to completely fill the void that exists behind the door frame and between the jamb stud of the framing system. Fully grouting the frame reduced the potential for acoustical flanking paths while damping the frame against vibration. Current practice is not with plaster but with high density mineral wool. However, this practice is generally limited to high acoustically performing walls, which employ doors fitted with acoustical gasketing.
The use of spot-grouting was for standard wall installations that used conventional doors. Here the discussion starts with understanding the terminology of the door frame itself. The throat opening of the frame is where the wall assembly fits into the frame. Looking at the profile of the frame, there is the face of the frame, the back bend, then finally the back bend returns. Some profiles do not include the back bend return and in that case, the back bend terminates at the gypsum panel. The face of the frame is what is visible when looking at the installed frame in elevation. The back bend is where the frame returns to the throat opening, and the back bend return is the portion of the frame that returns within the throat opening. The back bend return is then parallel and in very close proximity to the gypsum panel of the wall. The basic intent of the spot-grouting was to keep the frame from rotating and having the back bend return gouge the face of the gypsum panel.
There are two types of frames. The first is where the frame is installed before the wall framing, the second is termed a “knock-down” and is installed after the wall is complete. With either version, the frame must be designed for cold-formed steel framed partitions. The frame installed first comes from the factory with special brackets welded to the frame. The steel jamb studs are then mechanically attached to the bracket in the frame. The ANSI Standard A250-11, Recommended Erection Instructions for Steel Frames, calls for two #6 x 3/8-inch self-piercing tapping screws or steel drill screws per bracket. These brackets are typically located at three locations along both the hinge and strike side of the frame. With the frame installed first, the cold-formed steel framing is then put in place complete with jamb studs and a header. The size of the jamb studs and header is predicated by the size of the opening, the weight of the door, and if the framing is considered structural.
The gypsum panel must extend into the throat opening of the frame a prescribed distance. That distance can be a half-inch, which is required in fire-resistant installations. This is dictated in NFPA 80, Standard for Fire Doors and Other Opening Protectives. Spot-grouting then means a small amount of chemically setting joint compound is applied at the bracket location on the leading edge of the gypsum panel as it enters the throat opening. The joint compound then bonds the bracket to the gypsum panel and the frame. This is done on both sides of the wall and at each bracket location, and the intent is once again to provide added restraint against frame rotation. Certain ANSI standards and door frame manufacturers clearly state that the door frames should not be grouted. Also, if the wall is to be fire resistive or provide an hourly rating, then adherence to NFPA 80 takes precedence.
As mentioned earlier, spot-grouting has become somewhat archaic and is in conflict with recognized door frame standards. A contractor who finds this requirement in architectural specifications should first do some research to ascertain the need. It is recommended to contact the manufacturer of the specified door frame and get a written response on their current recommendation regarding spot-grouting with that particular frame. Prior to any installation, this should be discussed and a resolution made that is acceptable to all parties.
Robert Grupe is AWCI’s director of technical services. Send your questions to grupe@awci.org, or call him directly at (703) 538.1611.
