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IBC Chapter 6 — Types of Construction

Updated Mar 25, 2026

Five construction types (I-V) defined by fire-resistance ratings of structural elements: Type I (noncombustible, highest rated) through Type V (wood frame, lowest rated).

Section 602: Construction classification. Type I: noncombustible throughout, structural elements fire-rated. Type IA: structural frame 3-hr, bearing walls 3-hr, floor 2-hr, roof 1.5-hr. Type IB: structural frame 2-hr, bearing walls 2-hr, floor 2-hr, roof 1-hr. Type II: noncombustible, Type IIA: 1-hr structural, Type IIB: 0-hr. Type III: exterior noncombustible, interior any material. Type IIIA: 1-hr interior, Type IIIB: 0-hr. Type IV: heavy timber or mass timber. Section 602.4: Mass timber includes CLT, glulam, NLT, DLT, SCL with minimum dimensions. Type IV-A: 3-hr mass timber with noncombustible protection. Type IV-B: 2-hr. Type IV-C: 2-hr exposed. Type IV-HT: traditional heavy timber. Type V: structural elements of any material. Type VA: 1-hr rated, Type VB: 0-hr.

TAGS

IBC construction-type fire-resistance noncombustible mass-timber heavy-timber

DETAILS

types

["IA","IB","IIA","IIB","IIIA","IIIB","IV-A","IV-B","IV-C","IV-HT","VA","VB"]

code year

2024

code system

IBC

code section

Chapter 6

RELATED KNOWLEDGE

IBC 903.2.1 — Group A Occupancies (Sprinkler Requirements)

Automatic sprinkler system required throughout buildings with Group A occupancy where fire area exceeds 5,000 square feet, or overall building area exceeds 12,000 square feet, or occupant load of the fire area exceeds 300.

IBC 903.2.7 — Group M Occupancies (Retail Sprinkler Requirements)

Automatic sprinkler system required in Group M (mercantile) occupancies where fire area exceeds 12,000 square feet or building is more than three stories above grade.

IBC 903.2.11.3 — Buildings 55 Feet or More in Height

Automatic sprinkler system required throughout buildings with a floor level having an occupant load of 30 or more that is located 55 feet or more above the lowest level of fire department vehicle access.

IBC 1015.1 — Exit and Exit Access Doorways Required

Two exits or exit access doorways required from any space where occupant load exceeds the table values. Spaces with occupant load exceeding 500 require a minimum of 3 exits. Spaces exceeding 1,000 require 4 exits.

IBC 1017.2 — Exit Access Travel Distance

Maximum travel distance from any point in a building to an exit shall not exceed 200 feet unsprinklered or 250 feet sprinklered for most occupancies. Specific occupancies have modified limits.

IBC Table 601 — Fire-Resistance Rating Requirements

Specifies minimum fire-resistance ratings for structural elements based on construction type (Type I through V). Type IA requires 3-hour rated structural frame, 2-hour floors, and 1.5-hour roof.

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