Frequently Asked Questions

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 and requires a coat of primer.
• Galvannealed steel is basic 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 A50, 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 basic 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 of core 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 a general purpose door 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 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 situations where durability and security are important.
• 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 qualities than honeycomb and steel-stiffened core doors.

The R-values have been updated as a result of a change to the testing method of SDI 113 (Standard Practice for Determining the Steady State Thermal Transmittance of Steel Door and Frame Assemblies). In the previous version of the standard, only a portion of the door was tested. This method does not reflect operable conditions as it doesn’t test the entire door, or the 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.

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 ensured that doors that perform to the specific performance levels outlined in SDI 100 A250.8 will conform 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.

Seamless edge doors are specified primarily for aesthetic considerations. Vertical seam edge doors are the most common because there isn’t any subsequent filling or welding of the seam. Intermittently welded seams, ground smooth and filled, are a common method of producing a seamless-edge door and are an option from many manufacturers. Continuously welded seam doors provide an uninterrupted weld the entire height of the door edge with no added filler material. .

The fire rating of a door is determined from Table 715.4 of the International Building Code® (2009). In most cases, the door carries a rating less than that of the wall because it is assumed there will be no fuel-load (furniture, fixtures, storage) in front of the door. NFPA 80 stipulates that unused doors be removed and the opening filled with wall construction equivalent to the rated wall.

Labeled hardware is permitted to be used on any brand of fire door, provided that door is properly listed and labeled for that hardware application. For instance, a door listed and labeled for single-point locks cannot be fitted with panic or fire exit hardware. A door specifically listed and labeled for this hardware application must be used.

Where required by the code, smoke and draft control doors must be tested and listed in accordance with UL 1784. This is not a Steel Door Institute standard, but all SDI members do provide products compliant with UL 1784.

Only third party certification services can change the label after field inspection. An inspector has the right and authority to request that frames be broken out of walls or doors and be cut open to expose their contents as part of a re-certification assessment.

Yes. Fusable link louvers with a maximum size of 24” x 24” can obtain up to 90 minute fire labels.

Yes, NFPA 80 allows the drilling of specific holes for the application of hardware. No other modifications are allowed.

You may paint over an embossed label on a door or frame, unless prohibited by the specification.  However, it is never permissible to paint over a Mylar® label or applied metal label for a door or frame.  The reason is that once a label is painted over it is impossible to discern the label information. 

Every fire door must have a latching device, so you cannot remove a lock or latch from a labeled door and maintain the rating. Where a non-essential piece of hardware has been removed, the remaining holes must be filled with the same material as the door itself.

Any modification to a fire door may negate the rating. Generally speaking, a cosmetic repair of a fire rated assembly with non-flammable body putty is permissible. 

Full scale fire room experiments have shown that these forces generally result in a sort of equilibrium once the fire is fully developed where negative pressure in the room relative to the outside exists in the lower part of the room and positive pressure exists in the higher levels. The area where these two zones meet is known as the “Neutral Pressure Plane”. This plane is generally horizontal and the pressure in the room becomes increasingly more positive the higher it is measured above this plane and more negative with increasing distance below the neutral pressure plane.
In the case of fire door tests, there has been a substantial change over the last several years in recognition of the need to make tests more closely simulate the type of pressure profile that is felt to be a good representation of the way fires actually behave. It has been recognized that the level of pressure difference is less critical than the fact that it exists and tends to drive a flow of hot gases and flames out of the fire area. SDI 118-05 tests for both neutral and positive pressure.

Generally they are not required.  However, gaskets are required in smoke and draft control areas if such a requirement is adopted by local authority.

They must have a minimum of approved hinges, a listed and labeled self-latching device and a labeled self or automatic-closing device.

Generally speaking, no, but the requirement is a function of the individual manufacturers’ listing. Intumescent products are typically used for a smoke and fire barrier on wood doors and are activated by heat. Given the basic properties of steel (e.g. it expands when exposed to heat), sealants are not required on steel doors.

The required hourly rating will dictate the approved glass lites available. All glass used in fire rated doors must be listed glass, and be either 1/4" wire or other listed material. Basic guidelines on glass are as follows:

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.

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 performance over time.

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

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.”

ANSI A250.8 paragraph 4.2.2 addresses the grouting of frames.  The Steel Door Institute does not recommend grouting of frames, since often contractors will mix the grout into a pumpable solution, as opposed to the optimal consistency which is hand troweled.  Pumpable grout solutions contain too much moisture and can contribute to rusting of the frame from the inside out.  It is also important to note that grouting of frames is NOT required for fire-rated frames.

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 the gap at the bottom of a metal door is more than 3/4”, can the deficiency be overcome by adding an automatic door bottom or a metal astragal-like strip to the bottom edge of the 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.

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.

You are correct.  Bituminous coating adds an additional barrier for inhibiting rust.  Bituminous coating is applied to frames.

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 withdrawn and should no longer be used.  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.

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.

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 that sound can be transferred from one area to another. The STC scale is a logarithmic progression, meaning that, for instance, a jump of 3 points in an STC rating equates to a doubling in a door's ability to prevent sound transmission. Sound retardant doors are tested as a unit together comprised of the door, frame, hinges, and sound sealing system. See SDI 128-09 for more information. The following chart illustrates the sound retardant performance associated with a range of STC values.

Yes, SDI members do offer doors to FEMA 361.  Tornado resistant doors are not considered a standard product; they must be tested as a system including the hinge, door, and lock sets.  An architect/specifier should investigate the doors available that would satisfy the requirements for those openings. 

There are multiple levels of forced entry resistant standards; specifications may also require bullet resistant standards.  SDI does not have forced entry standards, which usually require a systems test.  ASTM has forced entry resistant standards; see their website for details.  Some SDI member companies manufacture doors to  various forced entry levels.