Frequently Asked Questions
How are fire resistance ratings for concrete determined?
I am reviewing a change of use request for a client
requiring verification of fire resistance ratings for a concrete
and masonry structure. The local code officials have asked for UL
numbers for the various building components in the structure. I
have contacted UL and have been informed that with the exception
of a limited number of proprietary building systems they have no
listings covering concrete and masonry building component fire ratings.
How are fire ratings established for generic concrete and masonry
building components and where can I locate the relevant information
for this verification process?
A:While UL is a good
source of information for fire safety of products, there is no
requirement for UL numbers regarding concrete and masonry construction
assemblies. Fire ratings for non-proprietary concrete and masonry
construction assemblies are determined based on the end point criteria
established in ASTM E119. This standard specifies the intensity
of the fire, the size of the specimen, and the criteria for determining
the end point of the test.
These criteria require that:
(1) the structure support its design load
throughout the test without passage of flame or hot gases, and
(2) the temperature of the unexposed surface (i.e., the surface
not exposed to the fire) not rise more than 139°C (250°F) as an
average nor 181°C (325°F) at any one point.
Extensive testing over many years led to the development of procedures
to calculate the fire ratings of walls, slabs, beams, and columns
constructed of concrete or masonry. The variables required for these
calculations are unit density of the concrete (unit weight), aggregate
type, and the section thickness for nonflexural
elements. For flexural members the variables are unit density, aggregate
type, section thickness, restraint conditions, and provisions for
clear cover requirements for steel reinforcement.
In addition there are methods for calculating the
fire resistance of flanged, ribbed and undulating sections, hollow
concrete and masonry sections, slabs and walls of multiple layers
of distinctly different concrete materials, multi-wythe
masonry walls, concrete and masonry fire protection assemblies for
steel columns, and the effect of finish materials applied to the
fire exposed side of these assemblies.
More information is available from the following references:
Methods of Determining Fire Endurance of Concrete and Masonry Members—Model
Code-Approved Procedures (SR267) or by calling 800.868.6733.
2) Standard Method for Determining Fire Resistance of Concrete
and Masonry Construction Assemblies, ACI 216.1, available at
www.concrete.org or by calling
3) American Society of Civil Engineers Standard Calculation
Methods for Structural Fire Protection, ASCE 29, available
at www.pubs.asce.org or by