The three most common steel types are cold rolled steel, galvanneal steel, and galvanized steel. Cold rolled steel, suitable for most interior applications, is uncoated steel with a factory applied coat of primer. Galvannealed (A40) steel is carbon steel coated with an iron-zinc alloy. It provides excellent corrosion protection when combined with a coating of quality prime paint and is adequate for most interior and exterior applications. SDI recommends use of the A Series, both A40 and A60, for primer adhesion. A60 is superior to A40 for inhibiting rust. SDI does not recommend the G series because of inferior primer adhesion properties. Galvanized steel is carbon steel treated with a full zinc alloy. It provides superior rust protection but has poor adhesion properties for prime or finish paint.
Archives: FAQs
Are steel doors always ordered with the latch prepared on the center of the edge?
All hollow metal doors are manufactured as two pans with an edge seam. Some are made with an offset concealed edge seam, which is 1/4″ from the push side of the door. This is suitable for the commonly specified mortise locks and mortise exit devices that have 1-1/4″ faceplates, and are automatically centered when abutted to the 1/4″ edge seam. (1/4″ 1-1/4″ 1/4″ = 1-3/4″).
Where is the recommended location of the electric hinge?
A hollow metal door manufacturer can locate the prep for an electric hinge at most any location a customer would desire. As the load bearing capacity of the reinforcement is reduced to accommodate the additional holes for the wiring, the middle location on a 3 hinge door would be recommended. The third hinge down on a 4 hinge door would be the recommended location. These locations also closely match the level of the strike.
What is the industry standard for weeps at the bottom of an exterior door with vertical stiffeners and mineral fiber insulation?
There is not an industry standard on weep holes. They are not required and not all manufactures incorporate such a configuration in their doors. If a manufacturer should determine that some sort of drain needs to be part of the door construction, how they accomplish that is up to them—whether by designing it into the door or by drilling holes/slots after manufacturing. A sealed flush cap on the top of the door should be requested if the opening is expected to be located in an area where moisture is expected (e.g. – exterior opening). Some holes in the bottom of the door are used by manufacturers to suspend the doors during coating operations.
What is the industry standard on exterior steel doors and water resistance?
SDI 127H contains information on water penetration. In summary, door assemblies are not manufactured to be watertight. Seals and thresholds are required to ensure water resistance of the opening assembly in normal environmental conditions. In situations where water penetration is a concern, the contractor must seal all joints that are exposed to the elements after the frame assembly is installed. Whenever possible, it is strongly recommended that glass and glazing be installed on the exterior rabbet of the frame assembly.
Is there likelihood of “dimpling” on the faces of a steel reinforced door?
Yes, whenever metals are welded there is significant heat involved, potentially resulting in surface imperfections. Most steel doors have the majority of the welding done on the hinge and lock edges in order to minimize imperfections on the faces.
How can “dimpling” caused by welding be avoided?
The most common method to minimize aesthetic imperfections is the utilization of projection welding versus spot welding. Both are forms of resistance welding, but projection welding utilizes a formed projection on one piece to localized the weld current and minimize the resulting imperfection. While this technique will minimize the imperfections, all welding tends to leave some degree of surface imperfection. More information can be found in the Aesthetics section of A250.8 Appendix B.
Does the door core selection have any effect on mitigating weld “dimpling”?
Yes, doors specified with vertically steel stiffened cores are prone to some level of surface imperfection due to the internal stiffeners being welded to the face sheets. Doors intended for more aesthetic applications should avoid vertically steel stiffened cores in lieu of a laminated polystyrene, honeycomb or polyurethane core.
Stud manufacturers are adding ribs and texture to provide equal deflection criteria, but are thinner on the web portion of the stud that the anchor is pressing against. Is this thin section dimpling/bending when the weight of the door swings and puts pressure on the anchors?
Transfer of door loads to wall studs may cause local buckling of the wall stud if the stud gage is too light. Additional jamb anchors will spread the load more evenly on the wall stud.
With the advent of equivalent gage studs, does the reduced metal thickness affect pressure fit anchors?
Reduced metal thickness may contribute to local buckling of the stud depending on the door weight and location of the performance enhancing features in the wall stud. Flange stiffening grooves and web embossments will resist local buckling if properly located.