Is the /- 3/64” tolerance on door width determined from the nominal or net dimension of the door leaf?

The /- 3/64” tolerance is applicable to the manufacturer’s net dimension. The net dimension may vary depending upon the manufacturers’ design, i.e. beveled hinge and lock edge, beveled lock edge, square hinge edge, or square hinge and lock edge. For a manufacturer with a beveled hinge and lock edge design, the math would look like this: A door is ordered at a nominal width of 3’0”; The net width of that door will be 35 13/16” The 3/64” tolerance means it can be 35 55/64” (widest) The – 3/64” tolerance means it can be 35 49/64” (narrowest) Even at the narrowest dimension, it would still be within the NFPA 80 tolerance of 1/8” on both sides—36.000 minus .125 (x 2) equals 35 3/4”. In SDI-117, figure E in section 5.1 the dimensions are based on the NET door width. In figure B of section 4.2 there are the dimensions and tolerances for the frame.

If the gap between the meeting edges of a pair of hollow metal doors is greater than 3/16” (1/8” plus the 1/16” tolerance), can the deficiency be overcome by applying a metal astragal? How about with fire rated doors?

For non-rated pairs of doors, there is no specific code requirement for a maximum meeting edge clearance. The end user or architect may approve clearances greater than 3/16”, but should consider the effect on security and appearance. For rated openings, the 3/16” meeting edge clearance is measured from the “pull” or “wide” side of beveled doors. The 3/16” is the maximum clearance allowed per NFPA 80, regardless of the use of a flat bar astragal. Listed wrap-around metal edges may be an option and should be installed in accordance with the edge or door manufacturer’s listing. The meeting edge clearance between double egress pairs of doors, measured from one side only, may potentially exceed 3/16” since the measurement would be from the “pull” side of one door to the “push” side of the other door. In this case, an allowance should be made for the degree of bevel.

What is the acceptable gap between leaves on a pair of exterior steel doors?

The clearance between the door and frame shall be a maximum of 1/8″ for both single swing and pairs of doors. Refer to section 2.1.8 in A250.8 for clearances for meeting edges and undercuts for non-rated and fire rated applications. Since these are exterior doors, an open gap is not recommended and weather-stripping should be provided to seal the perimeter and meeting edge of the opening