The Ghost of Building Codes Past: 50 Years of Code Evolution

The other day I was rummaging through a closet looking for something I never found, and instead I discovered something that was, a long time ago while I was in architecture school, my second-most-used reference book. It wasn’t about architectural history, or design theory, or building technology. It was the 1970 edition of The BOCA Basic Building Code [1]. In the mid-1970s, instructors at the Illinois Institute of Technology’s College of Architecture had the crazy notion that architecture students should understand building codes and use them when designing their projects. Everyone was required to buy a copy of BOCA. And what, some of you may be asking, is BOCA?

For much of the 20th century, three organizations published model building codes: the Building Officials and Code Administrators published the BOCA Basic Building Code, the Southern Building Code Congress International published the Standard Building Code (SBC), and the International Conference of Building Officials published the Uniform Building Code (UBC). Local jurisdictions adopted these codes on a mostly regional basis: north-central and northeastern jurisdictions tended to adopt BOCA, southeastern jurisdictions preferred the SBC, and western and some north-central jurisdictions went with the UBC.

All that changed in 1994, when the three code organizations joined forces to create the International Code Council and develop a single national model code. The final editions of the three “legacy” codes—the SBC, BOCA, and the UBC—were published in 1994, 1996, and 1997, respectively. They were replaced by the International Building Code (IBC), first published in 2000 and revised every three years since [2]. Most states, counties, and cities adopted the IBC, usually with modifications [3].

Finding the old BOCA book sent me down memory lane to my college years, but it also made me wonder how obsolete it might be. After all, a lot of stuff has changed over the past 50 years. In 1970, all architectural drawings were made by hand, all models were physical objects, and you needed to know a programming language such as Fortran to use computers―mainframe computers, that is, not personal ones, which didn’t exist yet.

Outside of architecture, cigarette smoking was allowed almost everywhere, including airplanes; the Interstate Highway System was still under construction; and push-button telephones were just starting to replace rotary-dial phones (and all telephone handsets were tethered to their phones by curly wires).

So I assumed building codes must have changed too. To find out how much, I compared the 1970 BOCA with the 2018 IBC.

The first thing I noticed was BOCA’s size and weight. BOCA is a compact book, with 493 pages, 9? inches by 6 inches by 1? inches thick, and weighing two pounds. The 2018 IBC is a giant in comparison, with 752 pages, 12? inches by 11? inches by 3? inches thick, and weighing more than seven pounds. With more than three times BOCA’s weight, the IBC must have a lot more stuff. Right?

Well, of course it does. Many topics covered in the IBC aren’t mentioned in BOCA, including atriums, accessibility, delayed egress, carbon monoxide alarms, climate zones, common paths of travel, covered mall buildings, foam plastic insulation, fuel cell power systems, helipads, intumescent fire-resistant coatings, low-energy power-operated doors, photovoltaic panels, and wheelchair spaces.

On the other hand, the 1970 BOCA included things we won’t find in the 2018 IBC [4], such as drive-in movie theaters, cast steel (“All castings shall be free of injurious blow holes.” I should hope so.), flammable film (more than three pages devoted to it [5]), and spiral slide fire escapes (sounds like fun!).

Another obvious difference between 1970 and 2018 was BOCA’s lack of metric units of measure. It wasn’t until 1975 that Congress passed the Metric Conversion Act, which effectively changed nothing, but it did create the United States Metric Board, which disbanded in 1982 after having accomplished nothing. Then, suddenly, in 1988, Congress passed the Omnibus Foreign Trade and Competitiveness Act, which required federal agencies to use the metric system by the end of 1992. For architects, the most significant result is that wine is sold in 750 ml bottles. [6]??????????

The IBC labels its occupancy groups in a logical, easy-to-remember way (A for assembly, B for business, E for education, etc.). BOCA chose an odd, seemingly random approach. BOCA’s Group A was high hazard, Group B was storage, and Group E was business. For the mercantile, institutional, and residential occupancies, IBC uses Groups M, I, and R, while BOCA used Groups C, H, and L. BOCA had no group for educational occupancies (IBC’s Group E); it lumped it into its assembly occupancy (labeled “Group F,” of course). Subgroup F-4 includes “all buildings used as churches, schools, colleges, and for similar educational and religious purposes.”

High-rise buildings as we know them had been around for at least a hundred years before 1970, yet the 1970 BOCA had no special requirements for them. The IBC devotes three pages (and as we know, IBC’s pages are two and a half times bigger than BOCA’s) to requirements for high-rise buildings. These include fire sprinkler systems, emergency systems (such as smoke detection, fire alarm, and standpipes), and fire service access elevators.

To calculate the number of occupants in a building, the IBC gives us 38 categories of occupancy loads. People’s lives must have been much simpler in 1970, because BOCA had only 12, and three of them were for various types of mercantile uses. All institutional uses were thrown into one category, with 150 square feet per occupant.

The way stair and door widths are calculated has changed. The IBC’s method is straightforward: For doors and stairs, provide 0.2 inches and 0.3 inches, respectively, for each occupant. Thus, if 150 people need to exit through a stair enclosure, the door has to be at least 30 inches wide (actually, 32 inches wide, the minimum width for most doors) and the stair has to be at least 45 inches wide.

BOCA’s method was far less precise. It was based on a “unit of exit width” of 22 inches (supposedly the width of a man’s shoulders) and a half unit of 12 inches. Doors and stairs were sized by the number of occupants allowed per unit of exit width, e.g., for business occupancies protected by sprinklers, 112.5 people per unit of exit width for doors and 75 people for stairs. Thus, 150 occupants would need a door of one-and-a-half exit units, or 36 inches, and a stair of two exit units, or 44 inches.

Tread and riser dimensions have also changed. In 1970, you could have 7?-inch-high risers in business occupancies and 7?-inch-high risers in assembly and institutional occupancies. Today, seven inches is the maximum for all three occupancies. While risers have gotten smaller, treads have grown. Treads could be as small as 10 inches for business, assembly, and institutional occupancies; today, 11 inches is the minimum. Does this mean people’s feet are getting bigger? Apparently they are. A recent study [7] shows that average shoe sizes have increased by two sizes over the past four decades. [8]

Guards at stairs used to be much lower and more open. Because BOCA’s guards [9] were a minimum of 30 inches above the stair nosings (compared to today’s 42 inches), and handrails?were from 30 to 33 inches above the nosings, guards and handrails could be and often were the same element [10]. Regarding openness, you could have as much as 10 inches between intermediate longitudinal rails and 6 inches between vertical balusters. Today, a sphere larger than four inches in diameter cannot pass between any two intermediate rails or balusters.

Here’s something I don’t expect to see in codes anymore: In certain fire districts, “all roof coverings shall be of asbestos, … asbestos felt, … or similar noncombustible … materials.” And “where warm air ducts pass through combustible floors, the surrounding space shall be tightly fitted with asbestos cement.” And a list of exterior veneers including “asbestos shingles” and “asbestos cement boards.” And “ducts and vents shall be constructed of … asbestos cement or other approved … materials.” Today’s architects are so terrified of the A-word that even my typing it the nine times in this paragraph made me uncomfortable. Yet, the 2018 IBC still talks about asbestos-cement boards and asbestos shingles (Table 1404.2) and asbestos in low-hazard storage (Section 311.3), as well as in several other places.

These nine items are hardly a comprehensive study of how building codes have evolved in 50 years; they are just nine significant ones that caught my attention. Smaller ones include the use of escalators as means of egress (BOCA allowed it for some occupancies, while IBC explicitly prohibits it) and the IBC’s allowance of longer travel distances to exits.

What are the lessons I learned from this code comparison? First, that not all code changes result in safer buildings, nor are they intended to. Changing occupant group designations just made the code more rational, and the revised way to calculate door and stair widths makes more sense than using exit units; neither of these changes affected safety. Many other code changes respond to changing technology, such as photovoltaic panels and intumescent coatings, or to new design challenges, such as atriums and covered malls.

Second, that the code changes that do improve safety are often the result of learning from tragedies and catastrophic building failures. For example, most if not all serious high-rise fires have occurred in buildings (or parts of buildings) that either weren’t sprinklered or had the sprinkler system temporarily deactivated [11]. As a result, the IBC now requires all high-rise buildings to be sprinklered. Similarly, I suspect that guard heights were increased because people were accidentally falling over the lower guards, and that risers were shortened because people were stumbling on the higher ones.

And third, that a lot of code provisions haven’t needed to change. For example, the minimum headroom in stairs remains 6'-8" (or, as BOCA quaintly puts it, “six and two-thirds (6-2/3) feet”) and the occupant load for courtrooms is still 40 square feet per occupant. Apparently, in the past 50 years, neither criterion has proven to be enough of a problem to warrant a change. Even slightly more stringent requirements, such as increasing the stair headroom to, say, 7'-0" (because people have been growing taller) or increasing courtroom occupancy loads to 30 square feet per occupant (because, I don’t know, people are getting skinnier?), would affect sizes of stairs and building floor-to-floor heights, and result in costlier buildings without making the buildings safer.

My dear old 1970 BOCA may not be useful in designing buildings anymore, but it is a good reminder that building codes are constantly evolving for many reasons: They are being made easier to use, they are keeping up with changing technology, and they are finding the appropriate balance between life safety and building cost.

Follow the author on Twitter @bill_schmwil.

Footnotes:

[1] What was Reference Book #1? Architectural Graphic Standards. It also cost more money than I had ever spent on a book.

[2] The IBC didn’t become the national building code. The U.S. Constitution leaves things such as building codes (and architects’ licenses) to the states, so the federal government hasn’t the authority to impose a national building code. And the National Fire Protection Association, which has been around since 1896 and has been publishing its Life Safety Code (under a variety of titles) since 1927, decided to produce its own model code, and in 2002 published NFPA 5000. This code is as comprehensive as the IBC, but is in many ways different. California briefly toyed with the idea of adopting it as the basis of the California Building Code, but in the end went with the IBC. NFPA 5000 is used in many countries, making it possibly more “international” than the IBC.

[3] Chicago was one of the last holdouts. In 2019, after 70 years of using its own quirky building code, the city has approved a major IBC-based overhaul, which will take effect in 2020.

[4] As near as I can tell, that is.

[5] And for good reason. Nitrate film, or nitrocellulose, was the material used for motion picture film from the industry’s beginnings until the early 1950s. It was able to capture great images―Citizen Kane and Gone with the Wind were shot with it―but it had the annoying tendency to burst into flame when subjected to heat from, say, a projection lamp. Nitrate film’s combustibility was a plot element in the movie Cinema Paradiso. In 1948, Eastman Kodak introduced cellulose triacetate, a far more stable film, and it replaced nitrate by 1951.

[6] The 1993 BOCA, the next-earliest edition available to me, has metric dimensions in parentheses.

[7] https://www.independent.co.uk/life-style/health-and-families/features/why-our-feet-are-getting-bigger-9481529.html

[8] A more likely reason for increased tread widths is that 7?" or 7?" risers are just not comfortable for most people to use. An old rule-of-thumb formula—24" ≤ 2R+T ≤ 25" (which was included in some building codes, such as the 1994 SBC)—provides a comfortable relationship between riser height and tread width. The rule of thumb dictates that, to stay within the 24"–25" range, as risers decrease, treads must increase. Thus, shorter risers may have had more to do with wider treads than people’s average foot size.

[9] “Guard” is the right term, not “guardrail.” Even in 1970, BOCA knew that, but most of us (including me) still habitually say “guardrail.”

[10] This resulted in elegant stair designs with all the railing elements meeting perfectly at every landing. To see classic examples of this, check out any Mies-designed building with a lobby stair. Say what you want about his buildings, but the guy knew how to design stairs.

[11] A notable example happened in 1991 in Philadelphia. One evening, a fire broke out on the 22nd floor of the 38-story One Meridian Plaza, across the street from the historic City Hall. By the time the fire department arrived the fire was already out of control. For 19 hours, the fire kept moving up, one floor at a time. The fire didn’t stop until it reached the 30th floor, which was the first floor protected by sprinklers.