Short answer: because the rules say both. Three different requirements cover elevator entrance markings in New York City, and every one of them asks for the marking on both jambs or each side of the frame. A single sign does not satisfy any of them.
We get asked about this, usually phrased as "why is the minimum two". It is not a merchandising decision. Here is each rule.
1. Floor designations, on both jambs
2010 ADA Standards, Section 407.2.3.1, Floor Designation:
"Floor designations complying with 703.2 and 703.4.1 shall be provided on both jambs of elevator hoistway entrances. Floor designations shall be provided in both tactile characters and braille. Tactile characters shall be 2 inches (51 mm) high minimum. A tactile star shall be provided on both jambs at the main entry level."
Two things in there are easy to miss. The floor designation is both tactile characters and braille, not a choice between them. And the star at the main entry level is also on both jambs, so the main egress floor needs a pair like every other floor.
The 2 inch squeeze
This is the detail that catches people ordering from a generic sign supplier. Section 407.2.3.1 sets a minimum of 2 inches for the tactile characters. But Section 703.2.5 sets the general rule for raised characters:
"Character height measured vertically from the baseline of the character shall be 5/8 inch (16 mm) minimum and 2 inches (51 mm) maximum based on the height of the uppercase letter “I”."
A 2 inch maximum, and a 2 inch minimum, applied to the same characters. For an elevator hoistway floor designation that leaves exactly one compliant height. Order a 1 inch character because it looked proportionate and it fails the hoistway rule.
The rest of the character spec
From Section 703.2 and its subsections: raised characters "shall be duplicated in braille complying with 703.3", must be uppercase (703.2.2), sans serif and "not italic, oblique, script, highly decorative, or of other unusual forms" (703.2.3), and raised 1/32 inch (0.8 mm) minimum above their background (703.2.1).
Section 703.3 requires braille to be contracted, Grade 2. Section 703.4.1 puts tactile characters between 48 inches minimum and 60 inches maximum above the finish floor, measured from the baseline of the lowest and highest tactile character respectively.
Our tactile and braille floor designation is made to that spec, any number or letter, star for the main egress floor, and it is sold in pairs because one jamb is not a compliant installation.
2. The star of life, on both jambs, on every floor
This one is New York City rather than federal. 2022 NYC Building Code Section 3002.4.2 covers the elevator sized to take an ambulance stretcher, and requires that it
"shall be identified by the international symbol for emergency medical services (star of life). The symbol shall be not less than 3 inches (76 mm) in height and shall be placed on both jambs of the hoistway entrances on each floor."
Note the last four words. Not the lobby. Each floor. On a twelve storey building that is twelve pairs for one car. Minimum 3 inches high, which is a different size from the floor designation above it, so they are not interchangeable parts.
That is the EMS star of life symbol, also sold in pairs.
3. The fire service helmet, on each side of the frame
2022 NYC Building Code Section 3007.6.5, Fire service access elevator symbol:
"A pictorial symbol of a standardized design designating which elevators are fire service access elevators shall be installed on each side of the hoistway door frame on the portion of the frame at right angles to the fire service access elevator lobby."
The same section adds that the symbol "shall be not less than 3 inches (76 mm) in height" and that "the helmet shall contrast with the background, with either a light helmet on a dark background or a dark helmet on a light background." The design itself is fixed by Figure 3007.6.5 in the code.
That is the firefighter symbol. Also a pair, also 3 inches minimum, also a different size rule from the floor designation.
So what does one elevator actually need
Per hoistway entrance, meaning per floor, per car:
- Two floor designations, tactile plus braille, characters exactly 2 inches, on both jambs. Every floor. The main entry level gets the star character.
- Two star of life symbols, 3 inches minimum, on both jambs, on every floor, if that car is the stretcher elevator under Section 3002.4.2.
- Two fire service helmet symbols, 3 inches minimum, on each side of the frame, if that car is a fire service access elevator under Section 3007.
Which is why the minimum on these three products is 2 and the step is 2. Buying one is buying half an installation.
What this article does not tell you
Whether your specific car is the designated stretcher elevator, or a fire service access elevator, is a question about your building's approved plans and its occupancy, not about signage. Sections 3002.4.2 and 3007.1 set out when each applies, and your architect, your elevator contractor or the inspector who cited you will know which your car is. We are not going to guess it from a product page.
If you already know what you need, every price and volume break is published. If you do not, the Code Finder narrows it, or send a photo of the jamb on WhatsApp.