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Rough Opening for Hollow Metal Frames

Rough opening size, kd frame: Take the nominal door width and add 2" and the nominal door height and add 1". Keep in mind that on a 3070 door, the nominal measurements are 3'0" x 7'0" while the actual measurements are 2' 11 3/4" x 6' 11 1/8". Using a 3070 door as an example, the rough opening size for a kd frame would be 38" x 85". This will allow the frame to wrap the wall 1" on all 3 sides so the RO can be a bit bigger but remember that the drywall must extend at least 1/2" into the frame at fire rated openings.

Rough opening size, kd frame cased open: Take the nominal door width and add 1 1/2" and the nominal door height and add 3/4" . Keep in mind that on a 3070 door, the nominal measurements are 3'0" x 7'0" while the actual measurements are 2' 11 3/4" x 6' 11 1/8". Using a 3070 door as an example, the rough opening size for a kd cased open frame would be 37 1/2" x 84 3/4".

Rough opening size, welded frame: Take the nominal door width and add 4 1/2" and the nominal door height and add 2 1/4". Keep in mind that on a 3070 door, the nominal measurements are 3'0" x 7'0" while the actual measurements are 2' 11 3/4" x 6' 11 1/8". Using a 3070 door as an example, the rough opening size for a welded frame would be 3' 4 1/2" x 7' 2 1/4". Since the standard face on a hollow metal frame is 2", the outside dimensions of a 3070 frame will be 3'4" x 7'2" so this RO dimension will give you 1/4" of "play" on all 3 sides. If you are installing a welded frame into a fire rated stud wall, remember that the drywall will have to extend at least 1/2" into the frame so you can not simply butt the drywall up to the frame at fire rated openings.