NOTE This standard covers hollow metal doors and frames fabricated from steel sheet for commercial, institutional, industrial, and government construction. (1.1)

NOTE It addresses flush, seamless, and embossed steel door faces over honeycomb, polystyrene, polyurethane, temperature-rise, or fiberglass-mineral-wool cores; knocked-down, welded, and slip-on frames; and the full range of duty grades defined by ANSI/SDI A250.8, Levels 1 through 4. Both interior and exterior applications are included, as are fire-rated assemblies with listings up to 3-hour labels, acoustic-rated assemblies, and galvanized and galvannealed substrates. In practice this covers nearly every commercial opening that is not wood or aluminum storefront. (1.2)

NOTE Two parallel North American standards bodies govern hollow metal, and both are legitimate. (1.5)

NOTE The Steel Door Institute (SDI) publishes the ANSI/SDI A250 series; the Hollow Metal Manufacturers Association (HMMA, a division of NAAMM) publishes the HMMA 800 series. The two systems are complementary, not competing — many commercial projects cite ANSI/SDI A250.8 as the primary product standard and use an HMMA guide spec as a section template. This standard adopts the SDI Level system as the practical basis for duty-grade verification and references HMMA documents where they govern installation and hardware location. A given project should hold to one nomenclature throughout to avoid requests for information. (1.6)

NOTE Wood doors, including veneered, solid-core, and composite stile-and-rail wood doors, are covered by Wood Doors and are not within this standard. (1.7)

NOTE Finish hardware — locks, latches, closers, exit devices, hinges, and electrified hardware itself — is covered by Door Hardware; this standard governs only the reinforcement and preparation for that hardware. (1.8)

NOTE Fire-rated vision-panel and sidelite glass is covered by Fire Rated Glazing, and interior glazing partitions and relites not attached to a hollow metal assembly are covered by Interior Glazing. (1.9)

NOTE Projects that bundle doors, frames, and hardware into a single combined package use Doors Frames And Hardware, which coordinates all three; this standard is the hollow-metal-only specification. (1.10)

NOTE Aluminum storefront doors, curtain wall, and non-fire-rated glass frames are outside this standard. (1.12)

NOTE Detention and security hollow metal beyond commercial grade — the heavy-gauge product line governed by ANSI/NAAMM HMMA 863 — is a distinct category and is noted here only as a scope boundary, not detailed. (1.13)

NOTE The ANSI/NAAMM HMMA 860 guide specification was under revision ballot in the 2024-2025 cycle and may supersede HMMA 861; verify the current published edition before specifying. (2.3)

NOTE Fire-rated assemblies shall be labeled by a nationally recognized testing laboratory and shall bear a permanent label identifying the rating and the test standard. (4.3)

NOTE The label is the only field-verifiable evidence that the assembly was tested as a unit. Any field modification that is not within the listing — drilling for unlisted hardware, enlarging a lite, or cutting the door height beyond the listed allowance — voids the label and requires re-listing or replacement of the opening. (4.4)

NOTE Duty grade selected for the opening governs the certified Level, which is validated by physical-endurance testing. (4.5)

NOTE ANSI/SDI A250.8 defines four Levels, and ANSI/SDI A250.4 prescribes the physical-abuse and cycle-endurance test that substantiates a Level claim. Specifying a Level without requiring the A250.4 basis invites under-built submittals that nominally cite the Level but were never tested to it. (4.6)

NOTE The steel substrate and coating shall be selected for the service environment of each opening, not assumed uniform across the project. (5.1)

NOTE Interior dry openings can use cold-rolled steel; interior humid or wet areas and any painted frame benefit from galvannealed steel, which holds paint better and resists corrosion at cut edges; exterior and corrosive-environment openings require hot-dip galvanized steel. Choosing a single substrate for the whole project either over-spends on interior doors or under-protects exterior ones. (5.2)

NOTE Thermal performance shall be specified for exterior openings in heating-dominated climates. (5.6)

NOTE A standard honeycomb-core door provides little thermal resistance. Polystyrene and polyurethane cores raise the assembly U-factor into the 0.35-0.59 BTU/hr·ft²·°F range and are appropriate for exterior openings in climate zones 4 and colder. If a core type is not called out, the fabricator will default to the least costly honeycomb core, and the thermal or acoustic intent is silently lost. (5.7)

NOTE Face-sheet thickness shall be specified as a minimum decimal thickness, not as a gauge number. (6.1)

NOTE Gauge designations are nominal and vary between manufacturers; a "18-gauge" sheet from one mill may be thinner than another's. ANSI/SDI A250.8 and the HMMA standards now express requirements as minimum decimal inch thickness for exactly this reason. Specifying by gauge alone allows an under-thickness substitution to pass review. (6.2)

NOTE Stainless steel hollow metal, when specified for hygienic or coastal applications, shall use Type 304 or Type 316 face sheets over a steel subframe in conformance with the applicable HMMA stainless guide. (6.4)

NOTE Stainless face sheets are used for hospitals, food service, and exposed coastal exteriors where galvanized steel is insufficient. Type 316 is specified where chloride exposure is severe. (6.5)

NOTE Doors shall be 1-3/4 in (44 mm) nominal thickness unless an acoustic, security, or other assembly requires a different thickness. (7.1)

NOTE The 1-3/4 in door is the commercial standard for the overwhelming majority of openings. The 1-3/8 in door is a light residential or closet leaf rarely seen in commercial work; 2 in doors appear in acoustic and high-security assemblies. Selecting a non-standard thickness drives custom frame profiles and longer lead times, so it should be a deliberate choice. (7.2)

NOTE Door face configuration (Model) is primarily aesthetic but affects sound attenuation and is specified by SDI Model. (7.3)

NOTE ANSI/SDI A250.8 defines three Models. Model 1 is full flush, a smooth face with no visible seam. Model 2 is seamless or center-seam, with the face sheets joined at a concealed seam for improved appearance. Model 3 is a stile-and-rail or embossed panel door, with pressed-in profiles that simulate a wood-panel door and is common in schools and public buildings. (7.4)

NOTE Core type shall be specified explicitly for every door, since it governs thermal, acoustic, and fire behavior. (7.9)

NOTE Honeycomb kraft-paper core is the standard interior filler. Polystyrene and polyurethane cores add thermal resistance, and polyurethane also adds structural stiffness. Temperature-rise cores limit the heat transmitted through a stairwell door during a fire. Fiberglass and mineral-wool cores provide acoustic mass. Because the fabricator defaults to honeycomb when no core is named, omitting the core selection is a common and costly error. (7.10)

NOTE Vision lites and louvers shall be located and sized on the shop drawings and shall not exceed the maximum permitted by the assembly's fire listing. (7.11)

NOTE For rated openings, the UL listing caps the maximum lite area and dictates the glazing product. An oversized lite voids the label. Louvers are generally not permitted in fire-rated doors except where specifically listed. Glass for rated lites is specified in Fire Rated Glazing. (7.12)

NOTE Frame type shall be matched to the wall construction, since anchorage and assembly method differ by substrate. (8.1)

NOTE A knocked-down (KD) three-piece frame is field-assembled and is the common choice for new drywall partitions. A shop-welded one-piece frame, with corners welded, ground, and filled, is specified for masonry, concrete, and high-abuse openings. A slip-on drywall frame is applied over finished drywall without rough-in and suits retrofit and light commercial work. Selecting a slip-on or KD frame for a masonry opening, or vice versa, produces anchorage that does not suit the wall. (8.2)

NOTE Frame throat dimension shall be verified against the actual wall assembly thickness, including finishes, before fabrication. (8.4)

NOTE The throat is the dimension across the back of the frame that straddles the wall. A nominal 4-7/8 in frame profile will not fit a 6 in CMU wall, and a single project commonly has several wall thicknesses; verify each condition separately. (8.5)

NOTE Frames installed in masonry shall be grouted solid at hinge and strike locations, at minimum, to resist deflection under hardware and lateral loads. (8.8)

NOTE An un-grouted masonry frame deflects under wall load and door operation, causing the door to bind and the latch to misalign. HMMA 840 requires grout fill at least at the reinforced hardware locations. A high-water structural grout can bow the frame faces. (8.9)

NOTE Doors and frames shall be reinforced, drilled, and tapped at the factory for the hardware in the approved hardware schedule, at the locations of ANSI/NAAMM HMMA 831. (9.1)

NOTE Factory preparation keeps labeled assemblies within their listing. Accepting standard hardware locations blindly leads to field modification of labeled frames, which then require re-inspection. A closer or exit device imposes far higher loads than a passage latch. (9.2)

NOTE Electrified hardware rough-in shall be provided in the hollow metal at the factory, never created by field drilling of a finished or labeled assembly. (9.3)

NOTE Electric strikes, maglocks, electrified hinges, and access-control devices require conduit knockouts, raceways, junction boxes, and through-bolt preparation built into the door and frame. Drilling these in the field after delivery — especially into a labeled assembly — voids the UL listing and damages the finish. (9.4)

NOTE Fire-protection ratings shall be provided where the International Building Code requires opening protectives, and the required rating follows the rating of the wall. (10.1)

NOTE IBC Section 716 prescribes the opening-protective rating for each rated wall or partition. Ratings range from a 20-minute corridor protective, through 45-, 60-, and 90-minute labels, to the 3-hour label required at a fire wall — a rating only hollow metal achieves. A 20-minute assembly is not the same as a fully listed fire door: under NFPA 80 it has different hardware and glazing allowances; treat each rating class as a distinct assembly type. (10.2)

NOTE Fire-rated door assemblies shall be tested and labeled to UL 10C positive-pressure criteria where required by the IBC. (10.3)

NOTE IBC Section 716 requires positive-pressure testing (UL 10C, equivalent to NFPA 252 under positive pressure) for fire doors in corridors and exit stairwells, which is effectively all rated hollow metal in commercial work. The legacy UL 10B neutral-pressure protocol remains valid only for the limited assemblies the code still permits. Positive-pressure listings typically require an intumescent edge seal as part of the listed assembly. (10.4)

NOTE Doors in exit stairwell enclosures shall be temperature-rise rated as required by IBC Section 716. (10.5)

NOTE A standard fire-rated door limits flame and smoke passage but does not limit the temperature of its unexposed face. IBC Section 716 requires exit-enclosure doors to be temperature-rise rated so occupants can pass a door with fire on the far side. The general limit is a maximum 450°F rise at 30 minutes; high-rise buildings require the more stringent 250°F limit. A standard fire label does not include this property, so it must be called out separately. (10.6)

NOTE Sound-rated openings shall be furnished as a complete listed assembly — door, gasketed frame, and seals — because the rating is a property of the assembly, not the door alone. (11.1)

NOTE A bare flush door carries an STC of roughly 28 to 32. An acoustic assembly reaches STC 38 to 42 with a continuous gasketed frame, automatic drop seal, and a mineral-wool or dense core; high-acoustic specialty assemblies reach STC 44 to 48. Specifying an "STC-rated door" without the gasketing and seals delivers none of the rated performance. (11.2)

NOTE Standard door sizes shall be used wherever possible, and oversized leaves shall be flagged as custom. (12.1)

NOTE A 3 ft 0 in (914 mm) wide single leaf at 7 ft 0 in (2134 mm) height is the commercial 80% case. Heights of 8 ft 0 in (2438 mm) are common; anything taller than 9 ft or wider than 4 ft triggers custom fabrication and engineering review, with longer lead times and reinforcement implications. Pairs run 5 ft 0 in to 6 ft 0 in overall. Treating an oversized opening as standard leads to schedule and structural surprises. (12.2)

NOTE Doors and frames shall receive a factory finish appropriate to the substrate and the field finishing intent. (13.1)

NOTE Most commercial hollow metal ships factory-primed for field painting. Where a durable factory finish is wanted, a powder coat or baked enamel is applied. Galvanized exterior assemblies may be primed over the coating or left for a galvanized-compatible field system. The prime coat itself is a tested product, not just paint. (13.2)

NOTE Manufacturer's physical-endurance testing shall substantiate the specified duty Level. (14.1)

NOTE ANSI/SDI A250.4 is the abuse and cycle-endurance test that backs a Level claim. The certification submitted under Quality Assurance is the project's evidence that the furnished product was actually tested to the Level specified, not merely cataloged at it. (14.2)

NOTE Completed fire-rated openings shall be field-inspected and documented per NFPA 80. (14.3)

NOTE NFPA 80 requires acceptance inspection of installed fire-door assemblies, and Authorities Having Jurisdiction increasingly require the inspection records as a condition of the certificate of occupancy. NFPA 80 also establishes the annual inspection regime that the owner must maintain over the life of the building. (14.4)

NOTE Field modifications that would void a fire label, including cutting, drilling, or welding outside the listing, are prohibited. (15.2)

NOTE Installed openings shall be adjusted so the door latches and operates without binding, sticking, or excessive force. (15.3)

NOTE HMMA 840 Section 7 sets the operational acceptance: a properly installed door swings freely through its full arc with hardware engaged. Binding usually traces back to an out-of-plumb or un-grouted frame. (15.4)

NOTE Doors and frames shall be delivered, stored, and handled per ANSI/NAAMM HMMA 840 to protect the finish and prevent rust and distortion. (16.1)

NOTE Hollow metal is easily dented and prone to surface rust if stored in standing water or stacked flat where moisture is trapped. HMMA 840 requires upright storage, off the ground, under cover, with spacers between units for air circulation. (16.2)

NOTE The manufacturer shall warrant the doors and frames against defects in materials and workmanship for the project's specified warranty period. (17.1)

NOTE The warranty covers fabrication and material defects — delamination, weld failure, core separation, and premature corrosion of properly maintained units. It does not cover damage from field modification, abuse, or failure to maintain the finish. (17.2)

NOTE Touch-up materials and selected spare units should be provided so the owner can maintain the openings without re-procurement. (18.1)

NOTE Touch-up paint matched to the factory finish lets the owner address minor field damage immediately, before rust starts. On larger projects, a small stock of spare frames or doors of the most common opening type shortens replacement time after damage. (18.2)