| TERM |
DESCRIPTION / DEFINITION |
| AAC |
Autoclaved Aerated Concrete. AAC is manufactured from sand, lime, and cement, to which is added a gas forming agent (water and aluminium paste). Tha aluminium paste reacts with the alkaline elements in the cement and forms hydrogen gas. The liberated gas expands the mixture forming extremely small, finely dispersed air spaces. The product is then shaped and cured under steam pressure in an autoclave. |
| ACR1: |
Axial Capacity Reduction Group 1.
The FRL associated with a system noted ACR1 applies when the timber studs are designed for reduced axial capacity. The reduction for particular studs are:
90 x 45 - 0%
90 x 35 - 0%
70 x 45 - 3%
70 x 35 - 8%
This may be achieved by increasing the design vertical load by the appropriate percentage. |
| ACR2: |
Axial Capacity Reduction Group 2.
The FRL associated with a system noted ACR2 applies when the timber studs are designed for reduced axial capacity. The reduction for particular studs are:
90 x 45 - 0%
90 x 35 - 10%
70 x 45 - 25%
70 x 35 - 35%
This may be achieved by increasing the design vertical load by the appropriate percentage. |
| ACR3: |
Axial Capacity Reduction Group 3.
The FRL associated with a system noted ACR3 applies when the timber studs are designed for reduced axial capacity. The reduction for particular studs are:
90 x 45 - 25%
90 x 35 - 30%
70 x 45 - 40%
70 x 35 - 45%
This may be achieved by increasing the design vertical load by the appropriate percentage. |
| ACR4: |
Axial Capacity Reduction type 4.
The FRL associated with a system noted ACR4 applies when the steel studs are designed for an axial capacity reduced by 5%.
This may be achieved by increasing the design vertical load by 5% |
| ACR5: |
Axial Capacity Reduction type 5.
The FRL associated with a system noted ACR5 applies when the steel studs are designed for an axial capacity reduced by 10%.
This may be achieved by increasing the design vertical load by 10% |
| ACR6: |
Axial Capacity Reduction type 6.
The FRL associated with a system noted ACR6 applies when the steel studs are designed for an axial capacity reduced by 15%.
This may be achieved by increasing the design vertical load by 15% |
| CAC |
Ceiling Attenuation Class is a measure of reduction in sound transmission, via the ceiling space, between two rooms. The measure is similar to that for Rw and STC. |
| Ctr |
Ctr is a “spectrum adaptation term” or adjustment factor to account for low frequency noise. The combination Rw + Ctr is useful for representing noise sources such as rock music, urban road traffic, distant jet aircraft and low speed rail traffic. It reflects the perceived sound reduction through an element subject to these typical urban noises.
Ctr is a negative number so Rw + Ctr will be less than Rw. It is not a constant and varies from system to system. |
| Deflection Limit |
A criterion applied to check the “serviceability” of a partition or ceiling system.
For a non-load bearing partition with “flexible linings” (ie; plasterboard) the BCA requirements for lightweight partitions H/240 (where H = wall height) provides acceptable serviceability.
Example: if wall height is 2700mm calculation is 2700/240 = 11.25mm max. lateral deflection at mid height of wall.
Normally where brittle finishes (ie; tiled bathroom) are applied to the partition the deflection limit is increased to H/360. For shelf loaded walls, the deflection limit is generally increased to H/480 to reduce the secondary effects of the shelf load.
Deflection limits can and do vary depending on the use and function of the building, and there are no prescribed limits for non-fire rated partitions. |
| DOS |
With respect to the Noise Reduction Coefficient of a ceiling system, Depth of System (DOS) is the overall distance from the ceiling lower surface to the top of the ceiling space. |
| Double Span and Continuous Span |
Double Span: Where a single member is supported at three points along its length.
Continuous Span: Where a single member is supported at four or more points along its length ie; a 6m length of furring channel suspended from a Top Cross Rail Grid system
Where double span and continuous span values are stated, the design assumes that all the spans are equal. |
| EFHI |
Early Fire Hazard Indices are expressed in the order: Ignitability, Spread of Flame, Heat Evolved and Smoke Developed. |
| FRL |
Fire Resistance Level (FRL) is the grading period in minutes for the criteria Structural Adequacy, Integrity and Insulation and expressed in that order e.g. 120/90/30. A dash (-) indicates no requirement for that criterion. Eg. -/60/60 means there is no requirement for Structural Adequacy and is used to indicate non-load bearing for a wall.
Isolated columns usually only require Structural Adequacy eg 90/-/- |
| Insulation |
In relation to an FRL, means the ability to maintain a temperature on the face not exposed to the furnace below the limits set in AS1530.4. In a test, this criterion would be exceeded if the average temperature rose more than 140 degrees above the starting temperature. |
| Integrity |
In relation to an FRL, means the ability to resist the passage of flames and hot gases to AS1530.4. In a test, this criterion would be exceeded when an element collapsed or developed cracks |
| Internal Pressure |
The design load applied to the soffit of the ceiling, either upward (uplift) or downward.
Sometimes this pressure may be due to the ceiling being used as a pressurised plenum for mechanical services.
The design load may vary in certain parts of buildings depending upon the exposure the ceiling has to the exterior, such as in factories with large roller doors etc. In these situations the contract specification should be consulted or clarification sought from the project coordinators. The direction of the design load is important so the ceiling requirements for “downstrutting” may be determined. Normally the deflection criteria are relaxed for ceilings subjected to wind loads.
Direct Fix Applications
The 0kPa table has been derived for use in residential type construction, where the ceiling is not directly exposed to the external wind load.
The 0.25kPa and higher wind load tables have been derived for situations where the ceiling is subjected to external wind loads, as would |
| Lateral Pressure |
The design load applied to the face of the wall.
The BCA requirements for lightweight partitions are sufficient for internal partitions in an effectively sealed building – 0.25kPa.
The design load may vary in certain parts of buildings (ie; lift shafts etc) and for certain building classes (ie; Class 9B buildings). Also, the design load may vary due to external wind load exposure, such as in factories with large roller doors etc. In these situations the contract specification should be consulted or clarification sought from the project coordinators. |
| Light Diffusion %(White Product) |
Light Diffusion is a measure of how well reflected light is spread. Low percentages indicate glare may be present at certain angles. Result is for standard white product. |
| Light Reflectance %(White Product) |
Light Reflectance indicates the percentage of light reflected from a product's surface. Result is for standard white product. |
| Ln,w+CI/Ln,w |
Weighted Normalised Impact Sound Level, Ln,w is a measure of noise impact performance of a floor/ceiling. It is determined in a laboratory and measures the impact sound transmitted by a tapping machine.
CI is a spectrum adaptation term to modify Ln,w to simulate foot steps on the floor.
Note that lower Impact Sound values indicate higher performance. |
| NRC |
Noise Reduction Coefficient is a measure of sound absorbed by a material. The single number represents an average of the sound absorption coefficients at 250, 500, 1000 & 200 Hz rounded to 0.05.
Values approaching 1.0 have the highest levels of absorption. |
| R-Value |
R- Value is a measure of thermal resistance of a material, that is the material’s ability to restrict heat transfer. It is the inverse of thermal conductance |
| RISF |
Ceiling systems may be required to provide 60 minutes Resistance to the Incipient Spread of Flame (RISF). This is the resistance of the ceiling membrane to insulate the space between the ceiling and the floor or roof above. This is to limit the temperature rise of materials in this space to a level which will not permit the rapid and general spread of fire throughout the space. |
| Rw |
‘Weighted Sound Reduction Index’ (Rw) is a single number used to rate the effectiveness of a system as a noise insulator. An increase in one Rw unit approximately equals a reduction of one decibel in noise level.
The Rw is determined by comparing the measured sound transmission loss (STL) curves of an assembly to reference Rw contours. Only a limited portion of the STL curve is permitted to fall below the Rw contour. The higher the Rw value the better the performance. |
| Rw/Rw+Ctr |
To present two BCA measures for acoustic rating in the system tables, the form Rw / Rw+Ctr has been used. For example, 59/51 refers to Rw = 59 and Rw+Ctr = 51
Rw, ‘Weighted Sound Reduction Index’, is a single number used to rate the effectiveness of a system as a noise insulator. The higher the Rw value the better the performance.
Ctr is a “spectrum adaptation term” or adjustment factor to account for low frequency noise.
Ctr is a negative number so Rw + Ctrwill be less than Rw. |
| Structural Adequacy |
In relation to an FRL, means the ability to maintain stability and adequate load bearing capacity in accordance with AS 1530.4. In a test, this criterion would be exceeded when an element collapsed or had excessive deflection. |
| Thermal Conductance |
Thermal Conductance is the time rate of heat flow per unit area between two parallel surfaces of a body under steady conditions, when there is unit temperature difference between the two surfaces. |