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• IBC 602.4

  Type IV

  • Type IV uses mass timber or noncombustible elements meeting Table 601 via 703.2; IV-A, IV-B and IV-C need noncombustible protection per 703.6 and 722.7; CLT labeled to ANSI/APA PRG 320. Above 12 stories or 180 ft, exit and hoistway enclosures are noncombustible.

  Works withIBC 703.2IBC 703.6IBC 722.7IBC 2304.11IBC 2303.1.4

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.1

  Type IV-A

  • IV-A elements are protected per 602.4.1.1 to 602.4.1.6.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2

  Type IV-B

  • IV-B elements are protected per 602.4.2.1 to 602.4.2.6.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.3

  Type IV-C

  • IV-C elements are protected per 602.4.3.1 to 602.4.3.6.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.4

  Type IV-HT

  • Heavy timber: noncombustible exterior walls with interior elements of solid or laminated timber or SCL, sized per 2304.11, without concealed spaces unless 602.4.4.3 is met.

  Works withIBC 2304.11

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.1.1

  Exterior protection

  • Outside faces of mass timber exterior walls need at least 40 minutes of noncombustible protection; wall coverings noncombustible except low-heat-release WRBs.

  Works withIBC 722.7.1

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.1.2

  Interior protection

  • All interior mass timber faces are protected per 703.3.

  Works withIBC 703.3

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.1.3

  Floors

  • Floors need at least 1 in of noncombustible material above the mass timber; undersides protected.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.1.4

  Roofs

  • Interior roof surfaces are protected; Chapter 15 coverings go outside.

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• IBC 602.4.1.5

  Concealed spaces

  • Concealed spaces hold only plenum-rated services and follow 718; combustible construction forming them is protected.

  Works withIBC 718IMC

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.1.6

  Shafts

  • Shafts follow 713 and 718, with both faces of mass timber protected.

  Works withIBC 713IBC 718

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.1

  Exterior protection

  • Outside faces of mass timber exterior walls need at least 40 minutes of noncombustible protection.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.2

  Interior protection

  • Interior mass timber faces are protected as this section requires.

  Works withIBC 703.3

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.3

  Floors

  • Floors need at least 1 in of noncombustible topping; undersides protected unless exposure is allowed.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.4

  Roofs

  • Interior roof surfaces are protected; in nonoccupiable spaces fully protected as concealed spaces.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.5

  Concealed spaces

  • Concealed spaces hold only plenum-rated services and follow 718.

  Works withIBC 718

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.6

  Shafts

  • Shafts follow 713 and 718 with both faces protected.

  Works withIBC 713IBC 718

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.3.1

  Exterior protection

  • Exterior faces of combustible walls need at least 40 minutes of noncombustible protection.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.3.2

  Interior protection

  • Interior mass timber may be left exposed.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.3.3

  Floors

  • Floor finishes per 804 may go on the floor construction.

  Works withIBC 804

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.3.4

  Roof coverings

  • Chapter 15 roof coverings are allowed.

  Works withIBC Chapter 15

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.3.5

  Concealed spaces

  • Concealed spaces hold only plenum-rated services; combustible construction forming them gets 40 minutes of protection.

  Works withIBC 718

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.3.6

  Shafts

  • Shafts, hoistways and exit enclosures get 40 minutes of protection inside and out.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.4.1

  Fire-retardant-treated wood in exterior walls

  • FRT wood framing and sheathing is allowed in exterior walls rated 2 hours or less.

  Works withIBC 2303.2

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.4.2

  Cross-laminated timber in exterior walls

  • CLT at least 4 in thick is allowed in exterior walls rated 2 hours or less, faced with 15/32-in FRT sheathing, ½-in gypsum or noncombustible material.

  Works withIBC 2303.1.4

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.4.3

  Concealed spaces

  • Concealed spaces must be sprinklered, filled with noncombustible insulation, or lined with ⅝-in Type X gypsum.

  Works withIBC 718IBC 903.3.1.1

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.4.4

  Exterior structural members

  • Heavy timber columns and arches may be used outside where fire separation distance is 20 ft or more.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.1.2.1

  Protection time

  • Noncombustible protection must contribute at least 80 minutes.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.2.1

  Protection time

  • Noncombustible protection must contribute at least 80 minutes.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.2.2

  Protected area

  • Some mass timber may be exposed: ceilings up to 100% of the unit or fire area's floor area, or walls up to 40%, or a mix per Equation 6-1; freestanding columns and beams are unrestricted.

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• IBC 602.4.2.2.3

  Mixed unprotected areas

  • With both exposed walls and ceilings: (ceiling exposed ÷ allowed) + (wall exposed ÷ allowed) ≤ 1.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

• IBC 602.4.2.2.4

  Separation distance between unprotected mass timber elements

  • Exposed mass timber walls must be at least 15 ft apart along the floor.

  International Building Code, 2024 · Chapter 6, Types of ConstructionRead the full text (opens UpCodes in a new tab)

Searches all 4,276 IRC 2024 sections, 5,532 IBC 2024 sections and defined terms (Chapters 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33 so far) and each city's local rules as they are added. Section numbers and titles from the International Residential Code and International Building Code, 2024 editions, copyrighted by the International Code Council; the IRC's electrical chapters (34 to 43) follow NFPA 70, the National Electrical Code. Requirements are summarized in our words (IRC Chapters 3 to 43, IBC Chapters 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33); read the full text at the link on each result. Local values come from each city's published documents.