FAQ’s

Modifications are only eligible when referenced and described in both the third-party certification and the manufacturer’s published instructions.

SDI recommends type A, both A40 and A60, over type G due to the superior primer adhesion qualities. A60 is superior to A40 for rust inhibiting.

SDI Technical Data Series 100 has been republished as an ANSI Standard, A250.8.In addition, please see our Technical Data Series 112 “Zinc-Coated Standard Steel Doors and Frames.” The difference in the A and G designations are explained. Table 1 of that document gives coding designations for A40, A60, G60 and G40.

Some Architectural Specifications require steel frames to be back-coated with a “bituminous” product for corrosion protection and sound control. The term “bituminous” is defined as an asphalt or tar material obtained as a residue from heat refined petroleum. For years it was not recommended by the Steel Door Institute for frames to be factory back-coated due to issues with packaging, shipping and handling. This procedure was more effectively accomplished at the jobsite by the contractor or appropriate trade immediately prior to installation of the frame.

Modern materials now offer manufacturers the opportunity to back-coat frames with a more user and environmentally friendly product. Some of these coating s are VOC (Volatile Organic Compounds) free and do not present the handling issues common to bituminous products. Today, multiple SDI manufacturers offer the option of factory back-coated frames which utilize these newer materials.

Per SDI-100-1991 the cores were listed as follows:
A – Kraft Honeycomb
B – Polyurethane
C – Polystyrene
D – Unitized Steel Grid
E – Mineral Fiberboard
F – Vertical Steel Stiffeners

These are now archaic references and should be treated as such.

The type of frame is up to the specifier’s discretion. To answer the question directly, knock down (K-D) frames are not standard for all openings, as many are specified as welded frames.

All frames shall be stored under cover. Assembled frames shall be stored vertically. The units shall be placed on at least 4″ (102 mm) high wood sills or in a manner that will prevent rust or damage, even if they are galvanized or primed. The use of non-vented plastic or canvas shelters that can create a humidity chamber shall be avoided.

The Department of Defense created the referenced document to provide a minimum level of protection from blast forces from acts of terrorism. The door assemblies offered by SDI members are specifically engineered and certified for these applications, with a wide variety of blast resistant capabilities. In order to supply the correct door assemblies, you will need to know the PSI/MSEC value (pounds per square inch / millisecond). This is a value that has been calculated by a blast consultant, and would be expressed as a numerical value, i.e. 50 PSI/MSEC. The higher the value the more blast force the opening is designed to withstand. Matching that value to a manufacturer’s certification will allow you to select the correct door, frame, glazing and hardware configuration.

Note: There are many other blast resistant specifications in addition to UFC 4-010-01. Please also keep in mind that the version of the specification is critical, particularly with the UFC 4-010-01 specification.

Yes, the primary focus of the Department of Defense’s Unified Facilities Criteria is to protect against injury from architectural glazing, so many SDI member companies have certifications for doors with glasslights.

There is nothing in the standards that prohibit veneers, but they would have to be documented within the manufacturer’s certification to ensure that they pose no hazard to the building’s occupants.

To properly specify the desired blast resistance for a door assembly, the following information needs to be provided:

  • Peak blast pressure — such as 5 psi.
  • Either the blast duration (e.g., 60 milliseconds) or blast impulse (e.g., 150 psi-msec).
  • Direction of blast pressure loading (i.e., either seated or unseated).
  • Acceptable level of post blast event damage: typically limited to Response Categories I, II or III. In general terms, these ratings correspond to (I) no permanent damage, (II) permanent damage but the door remains operable, and (III) more severe damage with the door being inoperable after the blast.

The ability to fire rate STC and blast doors would be specific to each manufacture and it is recommended that you contact a quality manufacturer for their specific listing. Follow this link to a listing of SDI manufacturers to ensure you are supplied a top quality door.

No, they are not the same, but they are both related to the construction of tornado shelters. FEMA 361“Design and Construction Guidance for Community Safe Rooms” is a guidance document, but FEMA does not regulate building construction. ICC 500 “Standard for the Design and Construction of Storm Shelters” is written by the International Code Council® and is referenced in the International Building Code in all Editions since 2009.

Many SDI manufacturers have single swing doors that are 4’0” x 8’0″, and pairs that are 8’0″ x 8’0″, listed with the Florida Building Commission. Special sizes are also permitted by the code to be analyzed by a Registered Design Professional if they fall outside of existing approvals.

As a general rule, the closer a building is located to the coastline, the higher wind speeds it is expected to experience. The wind speed and debris impact zones for Florida are defined by a map that is found within the Florida Building Code.

Hurricane resistance ratings are expressed in pounds-per-square-foot (PSF) values, and unlike fire ratings, there are no standard increments. In addition to the PSF values, they are either listed with or without “missile” impact ratings. In this instance, a missile refers to a 2 x 4 piece of lumber weighing 9 lbs. that is fired at the door at 35 miles-per-hour. A door assembly must withstand 3 impacts in order to have a missile impact listing. A typical door listing would be expressed as;

  • Design Pressure Rating +75/-65 PSF
  • Large Missile Impact – Yes

This listing indicates that the door assembly is rated for 75 PSF when loaded against the stops of the frame, and 65 PSF when loaded away from the stops of the frame

Some manufacturers have options for aesthetic finishes on these doors, but due to the severity of the testing requirements, almost all tornado shelter doors are very heavy-duty steel designs.

Yes, SDI members offer door assemblies certified to FEMA 361. These openings must be tested and installed as a system including the hinge, door, frame, anchors and latching hardware. The architect or specifier should investigate the doors available that would satisfy the requirements for those openings.

Openings, specifically hardware, have been tested to comply with FEMA 320 and 361 that have the bottom bolt engaging into the hardware rabbet of the frame. This eliminates the bottom rod engaging into the floor and can be single acting function that would comply with ADA requirements.

There are many variables that would determine the proper STC value, including the physical proximity of the office building to the airport. To ensure that the specification is properly developed, an acoustic consultant should be engaged to determine the Outdoor / Indoor Transmission Class (OITC) values.

STC ValueRatingDescription
50-60ExcellentLoud sounds heard faintly or not at all
40-50Very GoodLoud speech heard faintly, but not understood
35-40GoodLoud speech heard but hardly intelligible
30-35FairLoud speech understood fairly well
25-30PoorNormal speech understood easily and distinctly
20-25Very PoorLoud speech audible

No, we recommend that the door selection be made on the basis of the STC value that has been specified. Multiple door core types may be capable of achieving the specified value, and can be documented by Certificates available from the manufacturer.

OITC stands for Outdoor-Indoor Transmission Class and is a measure of the ability of a building material or product’s ability to retard sound transmission. It is similar to STC, but it is not the same. As the name indicates, OITC is a measure of sound transmission from the external environment into the building envelope. Testing to establish an OITC value utilizes ASTM E-1332 Standard Classification for the Determination of Outdoor–Indoor Transmission Class. This standard uses a range of frequencies lower than the STC testing, to more closely replicate the sounds of rail and vehicular traffic.

STC stands for “Sound Transmission Class”, a measure of the extent to which sound is prevented from being transferred from one area to another. The higher the STC value, the less sound transferred from one area to another.

The STC scale is a logarithmic progression, meaning that a jump of 3 points in an STC rating equates to a doubling in a door’s ability to prevent sound transmission. Acoustical doors are tested as an assembly comprised of the door, frame, hinges, and sound sealing system. See SDI 128 for more information.

The following chart illustrates the sound retardant performance associated with a range of STC values.

Most manufacturers conduct acoustic tests with grout filled frames to optimize the lab performance. Acoustic performance will be reduced on frames over STC 40 when grout or sound retarding material is eliminated.

TC is a single number rating that indicates the sound transmission loss over a defined range of frequencies of a door assembly between adjacent closed rooms. Higher values equate to better sound reduction performance.

Decibels dB, are used to express the intensity of a sound wave. Examples of decibels levels are:

  • 100-120 Deafening industrial machinery, jet engines
  • 80-100 Very loud cocktail party, boom box
  • 60-80 Quiet speech
  • 20-40 Faint soft whisper, recording studio
  • 0-20 Very faint acoustical laboratories, deep caves

STC ratings would be specific to each manufacturer and design, typical higher range ratings are between 50 and 55.

STC rated doors are generally supplied with a label that is either Mylar or metal, but the products are not listed like fire doors by agencies such as Underwriters Laboratories or Warnock Hersey. Labels are for manufacturer and rating identification purposes only.

Typically, doors with higher STC ratings have increased cost, weight and lead time.

Where the doors are fire rated, these clearances are regulated by NFPA 80, “Fire Doors & Other Opening Protectives”. The clearance between the door and frame shall be a maximum of 1/8″. The clearance between the meeting edges of pair of doors shall be 3/16″. The clearance from the bottom of the door to the bottom of the frame should be a maximum of 3/4″. The clearance between the face of the door and the stop shall be 1/16″. See SDI 100 A250.8-2.1.8 for complete specifications.

While the clearances of non-fire rated openings are not regulated by the Building or Fire Code, they typically will follow the same values as a rated door.

Refer to ANSI 250.8 paragraph 2.1.8 entitled “Design Clearance” and the subparagraphs underneath that. Those paragraphs specifically and clearly delineate and define the design clearances for between the door and the frame, between the meeting edges of pairs of doors, and the clearance measure from the bottom of the door to the bottom of the frame.

If a metal door has a gap between the meeting edges of a door pair that is greater than 3/16″ (1/8″ plus the 1/16″ tolerance), can the deficiency be overcome by applying a metal astragal?

If grouting is done properly it will not cause any issues with the frame. It will actually improve the sound deadening qualities. Unfortunately, thin pumpable slurry is often used and the excess water in it causes rust. Grout should always be hand troweled, never pumped.

For fire rated openings, you should verify with the frame manufacturer that if a bituminous coating is used to protect the steel frame against any corrosive effects of the grout its use will not negate the fire protection rating.

Grouting will not make a properly anchored frame any sturdier. In fact, drywall slip-on frames have passed fire and hose stream tests, cycle tests, and even impact tests with only anchoring.

No. Grouting should never be specified for drywall construction. When grout is drying, the moisture only has two places to go. The first is into the drywall, which weakens it. This could hinder the frame’s integrity or ability to retain anchors. The other place the moisture could go is into the hardware or the bottom of the frame, which may result in rust.

The final step in installing any frame is to double check for plumb and square before installing the door. Refer to SDI-122 for details.

Architects using hollow metal door and window frames on exterior openings sometimes incorrectly assume that frames are watertight. In fact, most seams in hollow metal frame construction are not welded nor sealed, unless by the painter. Many specifiers now write their specifications to include some of the following:

  • Full continuous TIG welds on all hollow metal frame joints, including both horizontal and vertical mullions. (Note: Not every shop is capable of TIG welds.)
  • Mullion construction with both joints of the two-piece mullion turned to the interior.
  • Continuous nailing flashing flanges on all framed construction with plaster to allow integral watertight flashing of the building paper to the nailing flange.

There are a small number of contract hardware and hollow metal distributors that have the capability to manufacture frames.

The distributor welds the frames in most cases. Many of them can modify doors and cut in glass light units as well. Distributors are often involved in fire labeling programs too, allowing them to label the door and frame.

Yes, ANSI A250.11 provides recommended erection instructions for steel frames. Please reference SDI-122 to troubleshoot an issue with a frame that has already been installed

It depends on a variety of factors such as the condition of the wall, reinforcements, and frame. You will also want to verify the gauges of the door and frame are compatible, and also that the hinge and strike locations match.

It is best to inquire with the door supplier for fire rated openings.

Most manufacturers can provide a Z-shaped anchor located just above the strike in the strike jamb.

The U.S. Green Building Council Leadership in Energy & Environmental Design (LEED) Green Building Rating System aims to improve occupant well-being, environmental performance and economic returns of buildings using established and innovative practices, standards and technologies.

Steel construction materials, including hollow metal doors and frames, typically generate credits in green building certification programs and reduce the building’s carbon footprint.

Materials & Resources Credit 4: Recycled Content intends to increase demand for building products that incorporate recycled content materials, thereby reducing impacts resulting from extraction and processing of virgin materials. Steel building products contribute positively toward points under Credits 4.1 and 4.2:

Credit 4.1 (1 point) “Use materials with recycled content such that the sum of post-consumer recycled content plus one-half of the pre-consumer content constitutes at least 10% (based on cost) of the total value of the materials in the project.”

Credit 4.2 (1 point) “Use materials with recycled content such that the sum of post-consumer recycled content plus one-half of the pre-consumer content constitutes at least 20% of the total value of the materials in the project.

Yes. All steel doors-honeycomb core, polystyrene core, polyurethane core and steel-stiffened core – are recyclable.

On the contrary, steel doors can be up to four times more energy efficient than wood doors. Steel doors and frames allow minimal air infiltration which results in less energy loss between the door’s interior and exterior surfaces. Steel is dimensionally stable and when properly designed, can provide an exceptionally tight building envelope for less air loss and better HVAC efficiency over time.

Steel is an infinitely reusable material without any loss of function, durability or quality. At the end of their useful life, about 88% of all steel products and nearly 100% of structural steel beams and plates used in construction are recycled into new steel products.

USGBC LEED, Materials & Resources, Section 5.1 and 5.2 provide the guidelines for the 500 mile minimum requirement. The guidelines expand beyond the location of the manufacturer to include where the materials were extracted and processed. Most architects agree that this is the most difficult credit to achieve due to the nature of the global economy.

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.

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.

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 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.

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 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

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 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.

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″).

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.

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.

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.

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.

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, 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.

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.

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.

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 gage, and edge construction are design attributes that contribute to the door assembly performance rating.

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.

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.

A quality bituminous coating should be applied to the throat of the frame.

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.

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.

Your specification should be very precise if there are unusual dimensions. For example, if an opening is 5’6” wide and the active leaf is 3’0” then your specification should state the dimensions of both leaves since they are different sizes.

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

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