Building Codes Hierarchy Reference

Why this matters

Trades work under a hierarchy of codes - national, state, and local - that govern almost every aspect of construction. The codes themselves are written by ICC, NFPA, and other standards organizations; they're adopted (often with amendments) by states and AHJs. Knowing which code applies, which edition is in effect, and where the customer's jurisdiction fits is the difference between a code-compliant install and a failed inspection.

The major model codes

ICC (International Code Council) family:

• IBC (International Building Code): general building structure, fire safety, occupancy. Commercial primary.
• IRC (International Residential Code): one and two-family dwellings up to 3 stories. Residential primary.
• IMC (International Mechanical Code): HVAC, mechanical equipment, ductwork in commercial; references IRC for residential.
• IPC (International Plumbing Code): plumbing in commercial; references IRC for residential plumbing.
• IECC (International Energy Conservation Code): building envelope, HVAC efficiency.
• IEBC (International Existing Building Code): existing-building modification.
• IGCC (International Green Construction Code): green building.
• IFC (International Fire Code): fire prevention.
• IECC, IPMC (Property Maintenance), IZC (Zoning): various.

Updated on 3-year cycle. Current as of writing: 2024 edition (2024 IBC, IRC, etc.).

NFPA (National Fire Protection Association) standards:

• NFPA 70 (NEC, National Electrical Code): electrical wiring and equipment. The bible of electrical work.
• NFPA 54 (National Fuel Gas Code, NFGC): gas piping and appliances.
• NFPA 13 (Sprinkler systems standard): fire sprinkler installations.
• NFPA 72 (National Fire Alarm and Signaling Code): fire alarm systems.
• NFPA 101 (Life Safety Code): occupancy / egress requirements.
• NFPA 70E (Standard for Electrical Safety in the Workplace): arc flash, electrical PPE.
• NFPA 90A/B (Air Conditioning): mechanical ventilation systems.
• NFPA 25 (Inspection / Testing / Maintenance): fire protection systems.
• NFPA 855 (Energy Storage Systems): batteries.

Updated on cycles varying from 3-5 years.

Other relevant standards bodies:

• UPC (Uniform Plumbing Code): alternative to IPC, adopted by some states (especially Western US). Published by IAPMO.
• ICC and IAPMO are the two major model code publishers for plumbing.
• OSHA (Occupational Safety and Health Administration): workplace safety; federal.
• ANSI standards: voluntary consensus standards, often referenced by codes.
• ASHRAE Standards: mechanical, energy efficiency. 90.1 (commercial energy), 62.1 (ventilation), 188 (Legionella).

How codes get adopted

Model codes are published by ICC, NFPA, IAPMO, etc. They are NOT enforceable until a jurisdiction adopts them.

Adoption pathway:

1. Federal: OSHA, EPA regs apply directly. Workplace safety, refrigerant handling.
2. State: legislature or state code body adopts model codes, often with state-specific amendments.
3. County/City: local AHJs adopt state code, sometimes with local amendments.
4. Local AHJ: building department interprets and enforces.

Latest edition is not necessarily in effect. A jurisdiction might enforce 2018 IRC even though 2024 has been published. Always check.

How to find what code applies

Step 1: Identify the AHJ (Authority Having Jurisdiction).

• Typically the city or county building department
• Sometimes a specialized authority (state plumbing board, electrical board)

Step 2: Ask the AHJ which edition is in effect.

• "What edition of the IRC do you enforce?"
• Get the year (2018, 2021, 2024)
• Get any local amendments

Step 3: Verify with the AHJ's website or by phone.

Step 4: Reference the specific code for the work being done.

State-by-state variations

Some highlights of which states use which:

IPC vs UPC:

• IPC adopted: most Eastern and Southern states
• UPC adopted: most Western states (California, Oregon, Washington), some Midwest
• Both adopted (different jurisdictions within state): a few

NEC adoption:

• All 50 states use NEC as baseline
• Cycle adopted varies: most enforce NEC 2020 or 2023; California sometimes 1-2 cycles behind
• Local amendments add or modify (Chicago has notoriously strict amendments)

Some jurisdictions don't enforce model codes:

• Some unincorporated rural areas have minimal or no code enforcement
• Some industrial sites have their own enforcement
• Federal property has federal enforcement

How codes are organized

Most codes are organized by chapter, with topical breakdowns:

IRC organization (residential code):

• Chapter 1: Administration
• Chapters 2-5: General Building (foundations, framing, roofs)
• Chapter 11: Energy Conservation (IECC integration)
• Chapters 24-25: Mechanical
• Chapters 27-31: Plumbing
• Chapter 32-43: Electrical (NEC integration)

NEC organization (electrical):

• Chapter 1-4: General requirements, installation
• Chapter 5: Special occupancies
• Chapter 6: Special equipment
• Chapter 7: Special conditions
• Chapter 8: Communications
• Chapter 9: Tables (conduit fill, conductor cross-section)

IPC organization (plumbing):

• Chapter 1: Administration
• Chapter 3: General regulations
• Chapter 6: Water supply
• Chapter 7: Sanitary drainage
• Chapter 9: Vents

When codes conflict

Common scenarios:

• Manufacturer instructions vs code: manufacturer instructions generally prevail when they exceed code (per "approved equipment" clauses)
• Federal vs state: federal takes precedence
• State vs local: state typically prevails, but local can be more stringent
• Conflicting code sections: AHJ interprets

When in doubt: ask the AHJ. Their interpretation is what gets the permit.

Permits and inspections

Permit required for:

• Most new construction
• Major renovations
• HVAC equipment replacement (most jurisdictions)
• Electrical service upgrade
• Plumbing fixture additions (most jurisdictions)
• Roofing replacement (varies)
• Structural modifications

Permit NOT required for:

• Maintenance / repair-in-kind
• Minor work (varies; check local definitions)
• Small electrical replacements (also varies)

Inspection types:

• Rough inspection: verify framing / wiring / piping before drywall
• Final inspection: verify completed work before occupancy / certificate of occupancy
• Pre-occupancy inspection: in some jurisdictions before customer can occupy

Failing an inspection means rework. Pulling a permit and following code prevents the rework AND protects the customer at sale time (unpermitted work depresses home value, may be revealed at inspection during sale).

References

• ICC (International Code Council) - model code publisher
• NFPA (National Fire Protection Association) - NEC and life-safety codes
• IAPMO - UPC and related model codes
• ASHRAE Standards - mechanical and energy
• State licensing boards - adoption status
• UpCodes (upcodes.com) - convenient online code reference
• Mike Holt Enterprises - NEC training and reference