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You are reading: Understanding FRLs: Fire-Resistance Levels

Understanding FRLs: Fire-Resistance Levels

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Key Insights

An FRL or Fire-Resistance Level is a term often used in construction and fire protection and commonly incorrectly written and interpreted.  FRL’s are an important metric used when describing the required passive fire protection rating to a buildings compartments and and key structural elements.  

Understanding FRLs are crucial to ensure the compliant design and construction of various building types in Australia.

What is an FRL? 

An FRL is defined in both the National Construction Code (NCC) and the Australian Standard (AS1530.4) as:

‘…the grading periods in minutes determined in accordance with Schedule 5, for the following criteria: structural adequacy, integrity and insulation, expressed in that order.’

In simple terms, this reading describes how long a building will stay up (structural adequacy), not let any fire or hot gases through (integrity) and stop heat from passing through (insulation). 

An FRL is expressed in the following format: X (minutes) / Y (minutes) / Z (minutes). X, Y and Z represent the number of minutes (from 0 – 240) a particular part of the building’s element is able to resist fire. FRLs are expressed in intervals of 30 minutes, with the maximum being 4 hours or 240 minutes.

 

The National Construction Code (NCC)

The NCC is Australia’s primary set of technical design and construction provisions in construction, specifying the minimum standards required for the safety, health, amenity, accessibility and the sustainability of certain buildings. The NCC specifies the requirements that each class of building component requires to ensure it is safely designed and constructed. 

The NCC’s Fire Resistance Performance Standards detail building requirements pertaining to their structural stability,  fire spread stopping capability, behaviour of included elements, conditions for safe evacuation and required service and emergency equipment. These requirements must be satisfied in order to achieve compliance, which can be done by a Deemed-to-Satisfy Solution (DTS) a Performance Solution, or combination of both.

  • Deemed-to-Satisfy describes using specified products which have been tested in accordance to AS1530.4 and have a corresponding report from an accredited testing laboratory to verify the product’s validity
  • Performance Solution describes the provision of additional information required from a certified structural or fire engineer, in the absence of an existing product certification or report, surrounding how the proposed system will satisfy the NCC requirements

 

What comprises an FRL?

The three metrics responsible for forming an FRL reading, as defined by the NCC are:

  1. Structural Adequacy: the ability to maintain stability and adequate load bearing capacity as determined by AS 1530.4.
  2. Integrity: the ability to resist the passage of flames and hot gases specified in AS 1530.4.
  3. Insulation: the ability to maintain a temperature on the surface not exposed to the furnace below the limits specified in AS 1530.4.

 

Structural Adequacy

This applies only to load bearing systems, with failure occurring at the time the tested material collapses or when the maximum rate of deflection exceeds prescribed limits. This reading is relevant to:

  • Load bearing fire rated walls
  • Load bearing fire rated floor systems
  • Load bearing shafts
  • Structural steel

In addition to the class of the building, an FRL is also determined by factoring in the structure’s spanning height/length, thickness and which edges are restrained.  

For non load bearing structures, this first portion of the FRL reading will be represented by a ‘-’. For example, the FRL for a non-loadbearing external wall of a Class 6 building that is between 1.5 to 3m will have an FRL reading of -/180/120.

What is an FRL? - Promat

 

Integrity

The aim of integrity is to ensure that no openings or gaps form that can allow flames or hot gases to escape through. Integrity failure can occur during testing when:

  • Flames are observed on the non-fire side for a period greater than 10 seconds
  • If a created gap exceeds a certain, specified distance
  • If a cotton pad, placed on a crack or opening for 30 seconds, glows or flames

The Integrity component of an FRL relates to structures such as walls, floors, windows, doors and frames as well as service penetrations.  

What is an FRL? - Promat

Insulation

Insulation pertains to the temperature that fire protection products reach when exposed to fire. Thermocouples, which measure temperature, are placed in certain locations on the specimen, with the locations varying depending on what is being tested. The failure criteria can be one of two ways:

  • The average temperature rise of certain thermocouples exceeds 140oK
  • Any individual thermocouple exceeds a temperature rise of 180oK.

These three components of an FRL are measured against the number of minutes a test runs before exceeding the failure criteria. The number of minutes recorded is then rounded down to the nearest segment of minutes for FRLs set out by the building code. This means that during a load bearing wall test, if the element was recorded to achieve 176 minutes of structural adequacy, this would be rounded down to the 120 minute segment, despite being only four minutes away from the 180 minute FRL achievement.

What is an FRL? - Promat

 

Service Penetration FRLs

The FRL of an element will also determine the FRL required for any service penetrations that element is exposed to. Fire protection to service penetrations is often an over-thought, but should be considered in the early phases of project design, to maintain the specified FRL of a structure. Failure to implement the correct FRL to a service penetration will negate the FRL of an element, regardless if correct measures had been applied to the element in the first place. 

The correct fire stopping solution for service penetrations will depend on many factors, but it is integral to ensure you are utilising the same brand of products used for the element in question and recommended to select products that have been tested and assessed in line with the test to AS1530.4 

Service penetrations FRLs do not require structural adequacy, and will therefore be represented with a ‘-’ as the first number of the FRL. 

Fire Stopping Solutions for Service Penetrations by Promat

Fire Stopping Solutions for Service Penetrations by Promat

 

Understanding Your Requirements

Designing and building structures that comply with the NCC is paramount for reducing risks and losses. Architects, Designers, Engineers, Builders and other stakeholders must have a thorough understanding of the requirements set out by the NCC when developing a fire safety design. Your fire safety requirements will be determined by the class of building according to the NCC, with factors such as the function of the building, its height, floor areas, fire load, evacuation time and occupant characteristics being considered.

Working with a certified, experienced professional early in your design phase is crucial to ensuring your project is compliant. Intimate, up-to-date knowledge of Australian Codes and Standards is required to ensure both your passive fire protection solution and products used are certified compliant and align with your building class. 

Leveraging the experience of a professional is important when designing, building, refurbishing, maintaining and repairing your site.  Considering a compliant fire protection system in the early phases of your project design works to ensure you have an optimal, pro-active solution, reduce costly rectifications, ensure compliance and reduce both safety and financial risk to your people and project.

 

Specification of PROMAT Certified Products 

Progressive Materials specify, supply and stock certified passive fire protection products, used to achieve required FRLs in a variety of industries and building types. We are the technical consultants and distributors of the PROMAT Fire Protection product range, which have been used in Australia for over 25 years on numerous high-value sites and projects. 

Our expert team work with Architects, Designers, Builders, Engineers and sub-contractors to recommend solutions and specify products required to help you achieve compliance. We offer passive fire protection products to achieve structural protection, fire compartmentation and fire stopping objectives. We also offer formal Passive Fire Protection CPD Training, conducted by industry experts designed to keep you up-to-date with the latest developments in the industry. Learn more here

Browse our passive fire protection product range or contact us to learn more or speak with a technical expert about your upcoming project. 

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