Classification of fire resistance in construction

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Fire resistance is the ability of a passive fire protection system or material to withstand a standard fire resistance test.

Fire resistance (FRR), on the other hand, is classified as the time, in minutes or hours,

that building materials or assemblies have withstood standard exposure to fire.

Under specified test conditions.

Characteristics of Fire Resistance Ratings (FRR)

FRR is a measure of the fire resistance of a material or assembly, determined by performing standardized fire tests and calculations.

There is also a Fire Rating Level (FRL), which is defined as the test result obtained after a fire resistance test has been performed.

Although FRR and FRL are used interchangeably,

FRR is the required design fire resistance value specified by a fire design engineer.

While the latter is the actual test value achieved after performing the test.

The FRR of building materials or systems is also specified by ASTM E119 or in accordance with Section 703.3.


Classification of fire resistance in construction
Classification of fire resistance in construction


The test sample is subjected to rigorous testing under controlled conditions to infer the corresponding FRR.

These exposure conditions may not match the real-world environments in the buildings.

The fire resistance rating of a building element depends on the following factors:

  1. FRL or product test results.
  2. The type of construction material used to make the item.
  3. The location of the element and its proximity to other building elements during a fire for example, it can be floors, ceilings, columns, walls or beams.
  4. The presence of non-combustible components near the building element.

How is FRR measured?

In order to determine the rates of resistance of materials to fire in a matter of hours,

the fire sets are installed in a temperature-controlled propane furnace,

and the temperature is increased over a specified period of time in accordance with the standards laid down in ASTM and Materials Standard E119

“Test Methods for Fire Tests of Materials Building and its materials.

This relationship between time and temperature is called the standard temperature-time curve.

Based on the time it takes for a particular material or structure to fail during a fire, fire ratings are calculated.

It is measured from when the element failure occurred,

this does not necessarily mean that the element was destroyed at that point.


Classification of fire resistance in construction
Classification of fire resistance in construction


The FRR of a substance is measured based on three criteria:

  1. Structural sufficiency: This is a stability test where the material continues to bear loads for the duration of the test.
  2. Integrity: This stage measures the ability of the material to remain intact without cracks or fissures when it catches fire.
  3. Insulation: This stage measures the material’s ability to slow down the spread of heat from one side to the other.

Suppose the design requirement for a material or system is FRR of 90, in this case, it means that the material must resist fire in three ways.

Stability, safety, and isolation, each for 90 minutes.

After testing, the FRL rating is represented by three numbers giving the time in minutes for each criterion, ie stability, safety and insulation.

In the following format _ / _ / _. For example, FRL with a value of 90/90/90.

If no FRL value is obtained, the standards with a lower value are refined to obtain a higher fire resistance rating.


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