Building Construction Types

Fireproofing and Construction Types

Fireproofing thickness is dictated by a variety of factors, mainly the size of the steel being protected, the product being installed, and the required hourly rating. This required hourly rating of a building is dictated by its construction type, this hourly number indicates the amount of time the installed passive fire protection system can withstand a standard fire test.

The following is a list of the various construction types and the required hourly rating on various construction elements.

TYPE I-A–Fire Resistive Non-combustible (Commonly found in high-rise buildings and Group I occupancies).

3 Hr. Exterior Walls*
3 Hr. Structural Frame
2 Hr. Floor/Ceiling Assembly 1 ½ Hr. Roof Protection

TYPE I-B–Fire Resistive Non-Combustible (Commonly found in mid-rise office & Group R buildings).

2 Hr. Exterior Walls*
2 Hr. Structural Frame
2 Hr. Ceiling/Floor Separation 1 Hr. Ceiling/Roof Assembly

TYPE II-A–Protected Non-Combustible (Commonly found in newer school buildings).

1 Hr. Exterior Walls
1 Hr. Structural Frame
1 Hr. Floor/Ceiling/Roof Protection

TYPE II-B–Unprotected Non-Combustible (Most common type of non-combustible construction used in commercial buildings).

Building constructed of non-combustible materials but these materials have no fire resistance.

TYPE III-A–Protected Combustible (Also known as “ordinary” construction with brick or block walls and a wooden roof or floor assembly which is 1 hour fire protected).

2 Hr. Exterior Walls*
1 Hr. Structural Frame
1 Hr. Floor/Ceiling/Roof Protection

TYPE III-B–Unprotected Combustible (Also known as “ordinary” construction; has brick or block walls with a wooden roof or floor assembly which is not protected against fire. These buildings are frequently found in
“warehouse” districts of older cities.)

2 Hr. Exterior Walls*
No fire resistance for structural frame, floors, ceilings, or roofs.

TYPE IV–Heavy Timber (also known as “mill” construction; to qualify all wooden members must have a minimum nominal dimension of 8 inches.)

2 Hr. Exterior Walls*
1 Hr. Structural Frame or Heavy Timber Heavy Timber Floor/Ceiling/Roof Assemblies

TYPE V-A–Protected Wood Frame (Commonly used in the construction of newer apartment buildings; there is no exposed wood visible.)

1 Hr. Exterior Walls
1 Hr. Structural Frame 1 Hr. Floor/Ceiling/Roof

TYPE V-B–Unprotected Wood Frame (Examples of Type V-N construction are single family homes and garages. They often have exposed wood so there is no fire resistance.)

Share your thoughts