NCC 2016 Volume One
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Section C Fire Resistance (Verification Methods)

Section C Fire Resistance (Verification Methods)

VERIFICATION METHODS

CV1

Compliance with CP2(a)(iii) to avoid the spread of fire between buildings on adjoining allotments is verified when it is calculated that—

(a)

a building will not cause heat flux in excess of those set out in column 2 of Table CV1 at locations within the boundaries of an adjoining property set out in column 1 of Table CV1 where another building may be constructed; and

(b)

when located at the distances from the allotment boundary set out in column 1 of Table CV1, a building is capable of withstanding the heat flux set out in column 2 of Table CV1 without ignition.

Table CV1
Column 1 Column 2
Location Heat Flux (kW/m2)
On boundary 80
1 m from boundary 40
3 m from boundary 20
6 m from boundary 10
Buildings on adjoining allotments

is a means to verify whether or not a building proposal achieves the requirements of in minimising the risk of fire spreading between buildings on adjoining allotments. A fire in one building should not cause the spread of fire to another building, because such fire spread potentially endangers public safety, health and amenity.

It is not compulsory for a designer to use . The designer has the choice of using:

  • to verify that a proposal achieves ;
  • the Deemed-to-Satisfy Provisions of Part C3; or
  • another means of verifying that will be achieved.

If is used to calculate the level of heat flux, it is important to calculate the level at all the points referred to in . The maximum level is not necessarily at the boundary. The size and shape of the openings will influence the level of heat flux.

Whether a material will ignite from radiant heat depends on the amount of heat and whether an ignition source (such as a spark) is present.

Examples

Examples

The following values give some typical examples of the amount of radiant heat necessary to ignite common materials used in buildings and their construction. Note, these figures should not be taken to be absolute, and may be subject to a range of variables.

  • Timber
    • Ignition in the absence of a spark 35 kW/m2
    • Ignition in the presence of a spark 20 kW/m2
  • Curtain materials
    • Ignition in the absence of a spark 20 kW/m2
    • Ignition in the presence of a spark 10 kW/m2

There are three mechanisms for transferring heat:

Conduction

Conduction is the transfer of heat from one source to the other when they are in contact.

Convection

Takes place when the flames or fire plume carry the heat to another body. Convection includes the carrying of embers from a burning body that can cause ignition of a second body.

Radiation

Radiation is the transfer of heat from one body to another. In essence this involves one body putting out enough heat to heat up another body without any form of contact, either directly or by way of flames or embers.

Radiation is the main mechanism for heat and fire spread between buildings.

By way of techniques developed in the field of physics, it is possible to calculate the amount of heat given off by a burning building. The answer depends on a number of factors, including:

  • the distance from the building;
  • the size and shape of the openings in the building;
  • the temperature of the fire, which will depend on the:
    • size of the fire, and
    • type of materials burning; and
  • the emissivity of any glass in openings in the building. The emissivity is, in comparatively simple terms, a measure of radiant heat reduction through a window opening. The maximum value is 1, but lower figures may be appropriate, depending on such factors as:
    • whether the opening is drencher protected, or
    • whether the opening is a fire window.

CV2

Compliance with CP2(a)(iii) to avoid the spread of fire between buildings on the same allotment is verified when it is calculated that a building—

(a)

is capable of withstanding the heat flux set out in column 2 of Table CV2 without ignition; and

(b)

will not cause heat flux in excess of those set out in column 2 of Table CV2,

when the distance between the buildings is as set out in column 1 of Table CV2.

Table CV2

Column 1 Column 2
Distance between buildings Heat Flux (kW/m2)
0 m 80
2 m 40
6 m 20
12 m 10

CV3

Compliance with CP2 to avoid the spread of fire via the external wall of a building is verified when—

(a)

compliance with CP2(a)(iii) to avoid the spread of fire between buildings, where applicable, is verified in accordance with CV1 or CV2, as appropriate; and

(b)

the external wall system—

(i)

has been tested for external wall (EW) performance in accordance with AS 5113; and

(ii)

has achieved the classification EW; and

(iii)

if containing a cavity, incorporates cavity barriers and these cavity barriers have been included in the test performed under (i) at the perimeter of each floor; and

(c)

in a building of Type A construction, the building is protected throughout by a sprinkler system complying with Specification E1.5 and has—

(i)

sprinkler protection to balconies, patios and terraces, and where overhead sprinkler coverage is not achieved alongside the external wall, sidewall sprinkler heads are provided at the external wall for the extent of the balcony, patio or terrace where overhead sprinkler coverage is not achieved; and

(ii)

for a building with an effective height greater than 25 m—

(A)

monitored stop valves provided at each floor level arranged to allow the isolation of the floor level containing the stop valve while maintaining protection to the remainder of the building; and

(B)

the sprinkler system being capable of providing sufficient flow to serve the design area (assumed area of operation) required by AS 2118.1 for the relevant hazard class on each floor level plus the design area (assumed area of operation) required by AS 2118.1 for the floor level above, except where the former level is—

(aa)

the floor level below the uppermost roof; or

(bb)

any floor level that is wholly below ground; and

(d)

in a building of Type B construction, the building is—

(A)

is protected throughout by a sprinkler system complying with Specification E1.5; or

(B)

has any openings in external walls separated by a slab or other horizontal construction complying with C2.6(a)(iv) as if the building were of Type A construction.

External wall of a building

CV3 is a means to verify whether or not a proposed external wall system achieves the requirements of CP2 in minimising the risk of fire spreading in a building and between buildings via the external walls of the subject building.

It is not compulsory for a designer to use CV3. The designer has the choice of using—

  • CV3 to verify that a proposal achieves CP2;
  • the relevant Deemed-to-Satisfy Provisions; or
  • another means of verifying that CP2 will be achieved

If CV3 is used, an external wall system must also be verified against CV1 or CV2, as well as meeting certain other fire safety measures, including ones specific to buildings of Type A and Type B construction.

Other fire safety measures are imposed in recognition that an external wall system tested to AS 5113 may contain combustible elements that still present a risk that needs to be mitigated in order to minimise the risk of fire spread via the external wall of a building.

The external wall system being tested to AS 5113 must reflect what is proposed to be installed, including cavities, cavity barriers, substrates and fixings. However, the external wall system being tested is not intended to include windows and doors.