Why building codes exist and how they work

Every building a construction manager delivers has to satisfy a set of minimum legal requirements for safety, health, accessibility and energy use. Those requirements are collected in building codes and the regulations that sit around them. A code does not tell an owner what to build or how beautiful it should be. It sets the floor below which no building may fall, so that the people who use it, the people next door and the firefighters who may one day enter it are protected whether or not they ever see the drawings. This first lesson explains why codes exist, how they are written, how they become law and how a construction manager uses them day to day.

The lessons that follow work through the code system in your country, permits and inspections, occupancy and construction type, fire separation, egress, fire protection, accessibility, structural and energy requirements, zoning and environmental approvals, and finally a code review of a small building. You do not need to memorize clause numbers. You do need to know how the documents are organized, which questions a code asks about every building, and how to find and apply the answer for the edition that governs your project.

A short history of building regulation

Rules about how to build are as old as cities. The Code of Hammurabi, written in Babylon nearly 4,000 years ago, punished builders whose houses collapsed and killed the owner. Medieval and early modern cities banned thatched roofs and required masonry party walls after great fires; London's rebuilding acts after the Great Fire of 1666 are the classic example. In North America, fires in wooden cities drove the first modern ordinances. Chicago burned in 1871, Boston in 1872, Saint John in 1877 and Toronto in 1904, and each disaster brought new rules on fire walls, roof coverings and the use of brick and stone.

Twentieth-century tragedies shaped many of the rules still in force. The Triangle Shirtwaist Factory fire in New York in 1911 killed 146 garment workers trapped behind locked doors and led to requirements for unlocked exits, outward-swinging doors and sprinklers. The Iroquois Theater fire in Chicago in 1903 and the Cocoanut Grove nightclub fire in Boston in 1942 shaped exit signs, panic hardware and limits on revolving doors. Hotel fires, collapses under snow and wind, and earthquakes added structural and fire protection requirements. Many sentences in a modern code can be traced back to a specific loss of life.

In the United States, three regional model code organizations grew up in the twentieth century: BOCA in the Northeast and Midwest, ICBO in the West and SBCCI in the South. In 1994 they joined to form the International Code Council (ICC), which published the first International Building Code in 2000. The ICC now publishes a family of model codes on a three-year cycle, and almost every state and large city bases its building regulations on them.

What codes are for

Codes protect people who cannot protect themselves by inspecting a building. A tenant cannot check the fire rating of the wall behind the drywall, and a shopper cannot see whether the roof was designed for the local snow load. Codes put those decisions in the hands of qualified designers and public officials, and they set the same minimum for every building of the same type. The main objectives are similar in both countries.

• Safety: limiting the probability that people will be injured by fire, structural failure, falls, electrical shock or other hazards in and around the building.
• Health: providing adequate air quality, sanitation, light, protection from moisture and control of noise between dwellings.
• Accessibility: making buildings usable by people with disabilities, including people who use wheelchairs, have low vision or are hard of hearing.
• Fire and structural protection of the building and neighboring property, so that a fire or failure in one building does not spread to another.
• Energy and water efficiency, now a core objective in both countries as governments set climate targets.

A code is a minimum standard. Owners may build to higher standards, and many do for durability, insurance, comfort or marketing reasons. A construction manager should never present code compliance as a mark of high quality; it means only that the building meets the legal minimum on the day the permit was issued.

Prescriptive and performance requirements

Code requirements come in two broad forms. A prescriptive requirement states exactly what must be provided: a stair riser no higher than a certain dimension, a wall with a stated fire-resistance rating, a guard of a stated height. Prescriptive rules are easy to apply and inspect, but they may not suit unusual designs. A performance requirement states what the building must achieve, such as limiting the spread of fire to the compartment of origin for a given time, and leaves the designer to show how. Performance rules allow innovation but require more analysis and more judgment from the official who approves them.

The International Building Code is mainly prescriptive, but Section 104.11 (Section 104.2.3 in some editions) allows the building official to approve alternative materials, design and methods of construction when the proposed design is satisfactory and at least equivalent to what the code prescribes in quality, strength, effectiveness, fire resistance, durability and safety. Research reports, such as ICC Evaluation Service reports, and engineering analysis are the usual evidence. The ICC Performance Code and NFPA 101's performance-based option provide formal frameworks for performance-based design.

Model codes, adopted codes and referenced standards

A model code is a document written by an expert body for governments to adopt. On its own it has no legal force. It becomes law when a government passes an act, regulation or ordinance that adopts it, usually with amendments. The legally binding document is the adopted code, and the edition that governs a particular project is normally the one in force on the date the permit application is made, subject to transition rules. Construction managers must always confirm which edition and which amendments apply; reading the latest model code when an older adopted edition governs is one of the most common professional errors.

Codes also adopt other documents by reference. Rather than repeat the full requirements for, say, sprinkler installation, concrete design or the testing of fire-rated assemblies, a code names a standard and an edition, and that standard becomes part of the code for the purposes of the referenced provision. A typical building therefore has to comply with dozens of standards that are never printed in the code itself. The edition named in the code governs, even if a newer edition of the standard has been published.

Common standards referenced in the I-codes include ACI 318 for concrete, AISC 360 for steel, the AWC National Design Specification for wood, ASCE 7 for structural loads, NFPA 13 for sprinklers, NFPA 72 for fire alarms, ASTM E119 for fire-resistance testing, ICC A117.1 for accessibility and NFPA 70, the National Electrical Code, for electrical installations.

Who uses the code

Codes are written for designers, officials and builders, and each uses them differently. Architects and engineers apply the code during design and certify that their drawings comply. Building officials review the drawings, issue permits and inspect the work. Fire officials enforce the fire code once the building is occupied. Contractors and trades build according to the approved drawings and the code requirements that apply to their work, such as stair geometry, firestopping and guard heights. Owners are ultimately responsible for keeping the building in compliance throughout its life.

A construction manager sits in the middle of this network. You will rarely design a code-compliant building yourself, but you will plan the permit schedule, coordinate inspections, catch site changes that affect compliance, manage substitutions of rated products, answer questions from officials and ensure that the as-built building matches what was approved. When a change on site affects a fire rating, an exit or an accessible route, you need to recognize it and route it back to the designers before it is built.

In the United States, states license architects and engineers, and most require a licensed design professional to seal drawings for commercial buildings above a size threshold. Building officials, plans examiners and inspectors are usually certified by the ICC, and many states require ICC certification for code officials. Contractors are licensed by states or cities, and some trades, such as electricians and plumbers, need their own licenses.

Reading a code

Building codes have a consistent structure, and learning it saves hours. Every code begins with administrative provisions explaining scope, application, definitions and how the code is enforced. The definitions matter more than beginners expect: words such as story, building area, grade, exit and fire separation have precise meanings, and a requirement can change completely depending on whether a space is defined as a floor area, a mezzanine or a story. Italic type, or a marker in electronic versions, usually shows that a word is defined.

When you look up a requirement, start with the scope of the part or chapter, check whether the building or space falls within it, read the requirement with its exceptions, then follow every cross-reference. Many provisions say what applies except in a stated case. Others are triggered only when a building is above a stated height or area, or when it is sprinklered. Write down the edition, article or section number and the exact wording you relied on, because a later reviewer will ask.

The International Building Code is organized in chapters. Chapter 1 covers scope and administration and Chapter 2 definitions. Chapters 3 to 6 cover occupancy, special uses, building height and area and types of construction. Chapters 7 to 10 cover fire-resistance-rated construction, interior finishes, fire protection systems and means of egress. Chapter 11 covers accessibility, Chapters 12 to 15 interior environment, energy, exterior walls and roofs, and Chapters 16 to 23 structural design and materials. Later chapters cover elevators, special construction, safeguards during construction and referenced standards. Sections are numbered by chapter, so Section 1017 is in Chapter 10 and deals with exit access travel distance.

Codes, standards, guidelines and best practice

Not every document on a construction site has the force of law. Codes and the standards they reference are mandatory where adopted. Manufacturers' installation instructions are often made mandatory by the code or by a product listing, and installing a rated product contrary to its listing can void its rating. Owner standards and specifications are contractual: they bind the contractor through the contract but are not enforced by the building official. Guidelines, design guides and best-practice documents are advisory. A construction manager must keep these categories straight, because the consequences of departing from each are different: a code violation can stop the work, a specification departure is a contract issue, and ignoring a guideline may only be poor practice.

Insurance requirements add another layer. Insurers and their engineering bodies, such as FM Global, publish data sheets that often exceed code requirements for sprinklers, roof attachment or flood protection. If the owner's insurer requires them, they become contract requirements, and a construction manager should identify them early because they affect cost and schedule.

Why the code changes

Codes are revised regularly to respond to new research, new products, new construction methods, losses from fires and disasters and changing public policy. Recent editions in both countries have added or expanded requirements for energy efficiency, mass timber construction, accessibility, protection from radon and, increasingly, resilience to climate hazards such as flooding, wildfire and extreme heat. Construction managers benefit from following code changes because they affect cost, scheduling of permits and the products that may be used. Lesson 12 explains how code changes are proposed and approved, and how you can take part.