Frequently Asked Questions
Door and Frame Construction
Steel doors typically lend themselves to a wider selection of builders hardware than do aluminum doors. They also provide more diverse options for fire ratings.
A quality bituminous coating should be applied to the throat of the frame.
Face welding is weld applied only to the face of the frame, usually at the 45 degree joint. The full profile weld is applied to the full contour of the frame at the intersection of the head and the jambs. Since most manufacturers can fire rate their frames knocked down (in 3 pieces), welding is not required and is usually for cosmetic appearance and ease of installation. Since the frame throat is sheltered by a wall on all sides, full profile welding is usually not required.
Galvannealed. Galvanized steel has that spangled look and is often found in weights of G40 and G60. You don’t want to specify it for your steel doors and frames because primer doesn’t adhere very well to it. Specify galvannealed steel at A40 or A60 instead because it offers excellent paint adhesion. In fact, when you specify to ANSI/SDI A250.8 then that’s exactly what you get.
Materials like fiberglass batt, mineral wool, strips of drywall, and acoustic coatings (e.g. Silent Running) may be added to the throat of the frame to improve acoustic performance. Performance may not equal that of a grouted frame.
Maximum Duty doors are listed as Level 4 in accordance with ANSI A250.8 and Physical Performance Level A in accordance with ANSI A250.4. The door core, hardware reinforcement, face gauge, and edge construction are design attributes that contribute to the door assembly performance rating.
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.
Transfer of door loads to wall studs may cause local buckling of the wall stud if the stud gauge is too light. Additional jamb anchors will spread the load more evenly on the wall stud.
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.
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.
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.
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.
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.
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.
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").
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 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.
Steel doors are differentiated by their core, with each type having a different set of properties and performance characteristics. The five most common cores are honeycomb, polystyrene, polyurethane, steel stiffened, and temperature rise.
- A honeycomb core door is used for interior and exterior openings where high thermal insulation is not required.
- Polystyrene core doors are the most commonly specified insulated core and are suitable for applications requiring an R or U factor (a measure of insulating performance).
- Polyurethane core doors provide superior insulating properties and are suitable for exterior openings in cold climates.
- Steel stiffened core doors feature steel ribs in the interior of the door and are ideal for high traffic, non-aesthetic applications.
- Temperature rise core doors are used when a fire resistance rating is required to retard the transfer of heat from one area to another (a stairwell, for instance).
The rough opening dimensions for a standard hollow metal frame are as follows:
- Assumes std. 2" face, butted wall.
- "A" = opening width + 4 1/2"
- "B" = opening height + 2 1/4"
So for a 3’0” x 7’0” door & frame, the rough opening would be 40 1/2" x 86 1/4"
R and U values relate to insulation performance characteristics. The higher the R value, and the lower the U value, the higher the insulating properties of the product. Polystyrene and polyurethane cores have higher insulating properties than honeycomb and steel-stiffened core doors. 1 ¾” thick commercial steel doors will have R values that range from approximately 1.5 to 3.
The R and U values have been updated as a result of a change to the ASTM testing methods of SDI 113 (Standard Practice for Determining the Steady State Thermal Transmittance of Steel Door and Frame Assemblies). In the previous test method only a portion of the door was tested, which does not reflect operable conditions of the door, frame and hardware. The new version of the standard tests the entire assembly, which represents real-world conditions. Architects should only use the numbers from the new thermal performance standard method.
The testing method was updated to enable architects and other design professionals to specify openings using real-world thermal performance data. Knowing the thermal conductivity of a door opening (U-value), allows you to specify according to the desired energy efficiency of a building or any applicable code requirements for the efficiency of the building envelope.
The references cited are from an outdated SDI 100 specification. The new specification, SDI 100 ANSI A250.8, does not contain letter designations for core material. The updated document provides a performance-based standard, such that an architect can be assured the doors will perform to the performance levels outlined in SDI 100 A250.8, regardless of core material. If an architect specifies a particular core material they will be limiting the number of manufacturers that supply that product, and perhaps the variety and styles of doors available to them. That is why it is better to base your choice on performance characteristics.
- vertical seam edge filled, dressed smooth,
- intermittently welded seams, edge filled and dressed smooth, or
- continuously welded seam, dressed smooth?
How do the three options differ?
Seamless edge doors are specified primarily for aesthetic considerations. Edge-filled and dressed smooth doors are treated with a filler material and subsequently sanded smooth and painted. Intermittently welded seam doors, are welded at intervals along the seam, treated with a filler material and subsequently sanded smooth and painted. Continuously welded seam doors provide an uninterrupted weld the entire height of the door edge with no added filler material and subsequently sanded smooth and painted.