NCC Tutor lesson - Understanding fire safety in the NCC

Slide 1

Understanding Fire Safety in the NCC.

NCC Tutor Series.

The focus of this presentation is on the fundamentals of fire safety in buildings, including fire safety terminology and the aims of fire safety provisions in the NCC.

This module is best viewed with a copy of the NCC on hand. To access the NCC, visit abcb.gov.au and register or log in to freely access it.

Slide 2

In this presentation you will learn:

• What causes fire?
• Approach to fire safety in the NCC.
• Key fire safety concepts and terminology.
• Active and passive fire safety measures.

We will also look at some useful resources.

Slide 3

Fire is the product of a chemical reaction and requires three key elements: oxygen, fuel and heat.

The fire triangle diagram presents a key concept that underpins fire suppression methodologies.

The removal or depletion of one of the three fire criteria stops the fire from continuing to burn. A fire will “burn out” when starved of oxygen, fuel or heat, for example when it has used up all the available oxygen or fuel, or when it is cooled to the point that the chemical reaction can no longer take place.

The provisions within the NCC make use of this understanding of what causes fire, and what can suppress it.

Slide 4

Fire safety in the NCC.

Fire is a major threat to life, health, and property, therefore, it must be considered in building design and construction.

The NCC fire safety requirements predominantly focus on:

• the safe evacuation of occupants before exposure to untenable conditions, and
• preventing damage to other buildings, that is minimising the spread of fire from one building to another.

‘Untenable conditions’are conditions in which human life is not sustainable due to prolonged exposure to smoke, heat or toxic gas.

Stopping the combustion process  contributes to fire safety in buildings, however it is not a critical requirement of the NCC.

The NCC also doesn’t facilitate comprehensive property protection. The NCC fire safety provisions do not require that the building is prevented from burning down, only that the occupants can safely evacuate and the fire doesn’t spread to neighbouring buildings.

Regulations addressing fire safety in buildings have been in place for nearly 2000 years. They haveevolvedover that time as a result of:

• learning from experience
• learning from research
• political expediency.

Current fire safety regulations can include measures that were used almost 2000 years ago.

The first major historical fire that lead to regulations being introduced were the Great Fire of Rome in 64AD, whenRome burnt for four days. Once the fire was extinguished, that then Emperor Nero implemented a new urban development plan designed to stop the spread of fire. These included:

• wider open roads
• restrictions on the height of houses
• more space between houses
• requirements to build houses in brick or stone, and
• no common walls allowed.

The second major historical fire was the Great Fire of London in 1666.Embers from a bakery chimney ignited a thatched roof on an adjacent building. London burnt for four days with 80% of buildings destroyed. Subsequently, fire control measures were introduced, including:
 

• hand-held water suppression – buckets and hand pumps
• fire breaks – created by pulling down buildings with hooks and ropes or controlled gunpowder explosions
• requirements to build houses of brick or stone
• wider streets, and
• the introduction of building surveyors to enforce these regulations.

Many of these same measures are essential parts of current fire safety regulations around the world.

Even now, the development of regulations of the built environment to minimise the impact of fire is an evolving process.

Slide 5

We’re going to talk about some key concepts that you need to understand in order to interpret the fire safety provisions of the NCC correctly.

The first of these is Fire-resistance Level, or FRL.  The fire-resistance level of a building element is a measure of how long the element can control or reduce the spread of fire, gases or heat and retain its own structural strength when exposed to fire.

FRL is a graded performance over time of a building element exposed to a test fire. It is measured in minutes and basically states how long a material or form of construction will last when subjected to a fire in a building. The Australian Standard AS 1530.4 is generally used to define a material’s FRL.

An FRL has three parts, each of which measure one aspect of the fire-resistance of an element.

• Firstly, Structural adequacy, which measures its ability to maintain stability and loadbearing capacity when exposed to fire.
• Next is Integrity, which measures how long it can resist the passage of flames and hot gases.
• And finally, Insulation, which measures how long the material can maintain a required minimum temperature on a surface not exposed to fire. That is, how long before other surfaces become too hot as a result of fire on another surface of the material.

If one aspect is not applicable, the FRL will include a dash (--) for that aspect.

For example 90/60/30 means that the material (or form of construction) will be structurally adequate - i.e. hold the load that it is carrying - for 90 minutes. It will maintain its integrity - i.e. will hold its shape or form - for 60 minutes and will insulate against heat from one side to the other for 30 minutes.

FRLs are specified for many materials, elements or assemblies in many different parts of the NCC. For example, in Volume One, they are specified in Sections C, D, E, G and H as well as in the State and Territory Appendices in the Schedules.

Schedule 5 of the various NCC Volumes contains the procedures for determining the FRL of different building elements.

Slide 6

Let’s explore how the FRL works by looking at a few questions.

Question 1: What level of structural adequacy must each opening have?

None of the listed types of openings in a fire wall must have any level of structural adequacy. That is, none of them need to comply with AS 1530.4 to maintain their stability and load bearing capacity in a fire.

Question 2: How (long) must each type of opening maintain a temperature on unexposed surfaces?

Self-closing or automatic closing doors in fire walls must maintain a temperature on unexposed surfaces for at least 30 minutes.

Windows - of any kind - and any other openings in fire walls have no requirement to maintain a temperature on unexposed surfaces for any time.  Although other requirements may apply.

This is the insulation portion of the FRL, i.e. the third value.

Question 3: How long must each type of opening resist the passage of flames and hot gases?

All the listed kinds of openings in a fire wall must resist the passage of flames and gases for at least 60 minutes.

This is the integrity portion of the FRL, i.e. the second value.

Slide 7

The second key concept to understand is fire-source feature. A fire-source feature for a building is a point:

• from which a fire could spread to the building, or
• to which a fire could spread from the building.

This includes the far boundary of a road, river or lake which adjoins the allotment, e.g. an allotment boundary that is on the other side of a street. It can also be the side or rear allotment of the boundary, even if no building or structure is on the adjoining allotment.

A fire source feature can also be an external wall of another building on the same allotment, besides a garage, shed, carport, etcetera.

The definition of external wall is slightly different for Volume One and Volume Two.

Note that as the illustration shows, Class 10 buildings or structures on a block are treated separately and are not included in the definition of a fire-source feature.

Fire-source features need to be identified so that appropriate fire safety measures can be taken to prevent the spread of fire.

Slide 8

Let’s apply both of the preceding concepts, FRLs and fire-source feature, and practice interpreting this information as it appears in the NCC. Consider this excerpt of
Table 3 Type A construction: FRL of building elements.  This is found in NCC Volume One, Specification C1.1 Fire resisting construction.

Question 1: What minimum FRL is required for an external wall in a Class 5, Type A construction building, if the wall is 2 m from a fire-source feature?

The FRL is 120/90/90.

Question 2:  What minimum FRL is required for an external wall in a Class 7b, Type A construction building, if the wall is 1 m from a fire-source feature?

FRL is 240/240/240.

Question 3: What is the relationship between the minimum insulation requirement of an external wall and the distance between the wall and the fire-source feature?

As the distance increases, the minimum requirements for insulation in an external wall of a Type A construction building decreases. The requirement for integrity reduces similarly, but only once the distance reaches more than 3 m. Minimum requirements for structural adequacy remain the same for a wall exposed to a fire-source feature, regardless of how far away that feature is. This holds true for any Class 2 to 9 buildings.

This means that an external, load-bearing wall in a Type A building must be able to maintain its structural stability and load-bearing capacity when exposed to fire or the same minimum time regardless of the closeness of a fire-source feature.

Slide 9

Combustible and non-combustible materials.The third key concept to understand is combustible and non-combustible materials and the differences between the two terms. Let’s look at non-combustible materials. Non-combustible materials, as per the excerpt on the slide, are defined in two parts: For a material; and for construction or part of a building.

Some examples are provided here on this slide.

Examples

• Cement: concrete block and tiles, mortar, cement render
• Stone: Slate roofing, building blocks, paving
• Ceramics: Tiles and fittings
• Metals: Sheet steel, copper, brass
• Glass (especially when tempered)
• Insulation: Some types of fibreglass and rockwool

Now, let’s look at combustible materials.

For the purposes of the NCC, any building material that doesn’t meet the definition of non-combustible is effectively considered combustible.

Like non-combustible materials, combustible materials are also defined in two parts: for a material; and for construction or part of a building.

Obviously for fire safety, a non-combustible material is better. However, not every material or building element is equally exposed to fire. So they don’t all need to provide the same level of protection.

Examples

• Timber: Framing, floors, doors, window frames, weatherboards, beams
• Many kinds of laminated façade or roof panels, especially those containing polyurethane or polystyrene
• Canvas cloth, such as awnings
• Adhesives and fillers
• Petrochemical based plastic and rubber products

Slide 10

Concession: Non-combustible materials.

Now, there’s a concession in the NCC for the use of non-combustible materials. Essentially the concession allows the use of certain combustible materials where a non-combustible material is required in the provisions.

The excerpt on the slide shows the relevant clause in NCC Volume Two, Part 3.7.1.1 General concession – non-combustible materials. There is a similar clause and list in NCC Volume One, Part C1.9(e).

This concession applies to the following types of materials, but is not limited to these materials only. It includes:

• plasterboard
• fibre-reinforced cement sheeting
• pre-finished metal sheeting that may have a combustible surface finish up to 1 mm thick with a spread-of-flame index not greater than 0, and
• some bonded laminated materials.

Slide 11

The fourth and final key concept to understand is fire hazard properties. Fire hazard properties capture the specific properties of a material - or assembly of materials - and how it performs when exposed to fire.

Fire hazard properties provide ratings for how:

• quickly a material - or assembly of materials - will catch fire
• how quickly the fire will spread once alight, and
• how much smoke is produced once that material is on fire.

Fire hazard properties are typically used to measure the performance of linings i.e.floor coverings of wall linings, to determine if they are appropriate for use in buildings.

As shown in the excerpt here from Schedule 3 Definitions, there are different categories of fire hazard properties defined in the NCC – these are in blue italics.  Each of these properties is either a Defined term in the NCC, or it references another section of the NCC. It is important to understand the meaning of each property, how it is derived and what it can be used for.

You need to ensure that the selected products meet these requirements. Generally, this will involve checking the manufacturer’s specifications, and perhaps organising an appropriate test of a material – you can check Schedule 3 for the standard that should be used.

Sometimes it may require the organisation of some kind of appropriate testing. If so, you should check Schedule 3 to ensure you understand which standard must be used. Schedule 6 Fire Hazard Properties also describes requirements for testing assemblies to AS/NZS 1530.3.

Slide 12

Let’s look at some questions to test your knowledge.

A material is what if it does not readily ignite or burn.

• Non-combustible

Building elements that could be exposed to fire are required to meet a minimum what.

• Fire-resistance level (FRL)

A what for a building is any feature from which fire could spread to the building, or to which fire could spread from the building.

• Fire source feature

A building material’s what indicate how that material will behave under specific fire test conditions.

• Fire hazard properties

Slide 13

To achieve fire safety in buildings, the NCC prescribes minimum fire safety requirements.

This is made up of individual elements that in combination form a fire safety system within the building.

A fire safety system may have one or more different elements, each of which could be targeted to one of the four aims listed below.

Active fire safety measures are those that are triggered when exposed to the products of fire such as heat, smoke or toxic gas; or which are manually operated.

Passive fire safety measures are those that do not respond or activate when subjected to fire or fire products. They are measures that are generally built into the building fabric and are focused on fire resistance.

What are active fire safety measures? Activefire safety measures are those that are triggered when exposed to the products of fire such as heat, smoke or toxic gas. This includes examples such as an automated smoke alarm.

Slide 14

Active fire safety measures are also those which are manually or automatically operated. For example, a fire extinguisher on a wall which must be manually operated. A smoke alarm triggers when it senses the presence of smoke.

Examples of active fire safety measures include:

• hose reels
• fire extinguishers
• fire blankets
• smoke alarms
• sprinklers
• break-glass alarms
• emergency lighting, and
• fire fighters/emergency services.

Remember, active fire safety involves exposure to a fire product – like heat or smoke which may precede the start of a flame.

Slide 15

What are passive fire safety measures? Passive fire safety measures are those that do not respond or activate when subjected to fire or fire products.

These measures are focused on fire resistance – they are all about:

• resisting ignition in the first place, and
• preventing the spread of flame if a fire does occur.

They include:

• fire rated walls, roofs, floors, doors, or stairways
• compartmentation- i.e. dividing large spaces into separate fire compartments
• use of non-combustible cladding, and
• providing open space between buildings and potential fire sources. 

They are generally part of the building fabric and are required to have one or more of the following attributes:

• fire-resisting materials
• resistance to the incipient spread of fire
• non-combustibility
• smoke hazard properties
• smoke-proof, or
• solid core.

Slide 16

Fire safety measures in NCC Volume One and Volume Two are designed to allow for safe evacuation and to limit the spread of fire.

However, because the types of buildings and their use across the two Volumes are different, there are some differences in the fire safety provisions. There is no one size fits all approach with any aspect of building design and the same is true for fire safety design.

Volume One covers a broad range of building classifications and uses, so there are different risks associated with fire.

Some building classifications are associated with inherently risky activities, from the point of view of fire, such as manufacturing or laboratory work. Warehouse buildings and other commercial buildings can also store flammable materials, or items that give off toxic smoke. There is an increased risk of fire in these types of buildings, and an increased risk to health and amenity for the occupants and users of the buildings. The fire safety measures required in these classes of buildings reflect that increased risk.

Class 2 to 9 buildings can also be large buildings and multi-storey buildings, which increases the time it takes to evacuate the building in the case of a fire. Fire safety measures need to take into account the need for the occupants to have a longer timeframe to evacuate safely than might be required in a smaller building.

Similarly, in some of these classes of buildings the occupants may be incapacitated, for example in a hospital or residential care home.  When occupants need assistance to evacuate, then evacuation will take longer, so this needs to be considered in the design and construction of fire safety measures.

Additionally, in Class 3 apartment buildings, Class 2 buildings or Class 4 parts of a building, occupants may be asleep at the time the fire occurs, so they need to be alerted to the fire, and given the time to evacuate safely.

Key responses to these fire associated risks in Class 2 to 9 buildings include those listed on the slide

Key Responses

• Fire compartments
• Use of non-combustible materials
• Smoke alarms
• Sprinkler systems
• Range of manual responses – extinguishers, blankets, etc.

NCC Volume Two covers a smaller range of building classifications - predominantly housing -with different risks, but there are still fire risks nonetheless.

Some of the activities that typically take place in Class 1 and Class 10 buildings can cause a fire, for example, cooking which is a common cause of house fires. Other common causes of house fires are:

• outdoor barbeques or other outdoor fires
•  overloading of electrical circuits- too many plugs into one outlet
• smoking, particularly in bed.

Occupants of Class 1 buildings may also be asleep at the time the fire occurs, so they need to be alerted to the fire, and given the time to evacuate safely.

Evacuation can generally be quicker, however because Class 1 buildings tend to be smaller than say a commercial building and only one or two storeys high. So, not as much time is needed to evacuate the building.

Key responses to these fire associated risks in Class 1 and 10 buildings are included and shown here.

Key Responses

• Separation of buildings
• Use of non-combustible materials
• Smoke alarms
• Range of manual responses – extinguishers, blankets, etc.

Slide 17

Other useful resources. There are some ABCB Standards related to fire safety, particularly for NCC Volume One. As with all other referenced documents, these are mandatory.

The ABCB also provides a range of handbooks, that contain non-mandatory guidance information.

Similarly, there are case studies, videos and other resources available from the ABCB website that might be useful to you. These do not contain any mandatory requirements.

Let’s test your knowledge.

Slide 18

What three inputs are needed to sustain a fire?

Oxygen, heat and fuel. All three inputs are required to sustain a fire, so fire safety measures in the NCC are generally targeted towards reducing one or the other of these inputs.

Slide 19

[Question] The fire safety provisions of the NCC are designed to:

• save people from death or injury and save buildings from burning down in a fire, or
• warn building occupants, allow them to evacuate safely and stop a fire from spreading to other buildings or structures
• warn building occupants, allow them to evacuate safely and stop a fire from burning the building down, or
• stop buildings from catching on fire and save people from death or injury.

Take a moment to consider your answer.

Answer: warn building occupants, allow them to evacuate safely and stop a fire from spreading to other buildings or structures

Yes that’s right. The fire safety provisions of the NCC are designed to save lives by allowing occupants to evacuate safely and reduce the spread of fire, but not to prevent the building from burning down.

A building that is on fire remains structurally stable for long enough for occupants to evacuate, and that the conditions within the building allow for safe evacuation. The fire safety measures are not designed to put a fire out or stop it from progressing entirely.

The fire safety provisions also try to reduce the spread of fire from one building to another, but this again means that one building can burn down, as long as the chance of the fire spreading to the neighbouring buildings is reduced.

Slide 20

Let’s summarise the key points of this presentation.

Remember the concept of fire source features? These expose a building to the risk of fire from outside the building. They can also result in fire passing from one building to another.

Appropriate fire safety rated materials and elements must be used for relevant situations or locations. Buildings can also be protected by both active and passive fire safety systems.

Also remember the other key concepts such as fire-resistance levels, non-combustible and combustible materials, and fire hazard properties. These concepts all contribute to the characteristics of different materials and assemblies.

Finally, there is a concession that may allow for the use of some combustible materials where a non-combustible material is normally required.

This brings us to the end of the presentation.

Slide 21

Thank you for viewing this NCC Tutor module. Check out the other NCC Tutor modules available to build your understanding of the NCC.