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4.2
Part 4.2 Footings, slabs and associated elementsPart 4.2 Footings, slabs and associated elements
4.2.2
Site classification
2019: 3.2.4.1
4.2.2
Site classification
2019: 3.2.4.1
The foundations where footings and slabs are to be located must be classified in accordance with AS 2870.
Explanatory information
Explanatory Table 4.2.2 provides a general description of foundation soil types that will assist in the classification of a site. More detailed information, including differentiation between classifications, can be found in AS 2870 or alternatively contact the appropriate authority.
Due to the limitations of this Part, if a site is classified H, E or P then reference must be made to AS 2870 for design and construction information.
Class | Foundation |
---|---|
A | Most sand and rock sites with little or no ground movement from moisture changes |
S | Slightly reactive clay sites with only slight ground movement from moisture changes |
M | Moderately reactive clay or silt sites which can experience moderate ground movement from moisture changes |
H | Highly reactive clay sites which can experience high ground movement from moisture changes |
E | Extremely reactive clay sites which can experience extreme ground movement from moisture changes |
A to P | Filled sites — see AS 2870 |
P | Sites which include soft soils, such as soft clay or silt or loose sands; landslip; mine subsidence; collapsing soils; soils subject to erosion; reactive sites subject to abnormal moisture conditions or sites which cannot be classified otherwise. |
Table Notes
- For Class M, further division based on the depth of expected movement is required.
- For deep-seated movement, characteristic of dry climates and corresponding to a design depth of suction change HS, equal to or greater than 3 m, the classification must be M-D.
- If classification M-D is established due to further division, design of footings and slabs is beyond the scope of the ABCB Housing Provisions and reference must be made to AS 2870 for design and construction information.
4.2.3
Excavation for footings
2019: 3.2.2.1
4.2.3
Excavation for footings
2019: 3.2.2.1
Notes
In New South Wales requirements for shoring and adequacy of excavation works are a prescribed condition of development consent. In addition consent authorities can place specific controls on siteworks associated with the construction of a building, by imposing further conditions of development consent.
Excavation for footings
4.2.4
Filling under concrete slabs
2019: 3.2.2.2
4.2.4
Filling under concrete slabs
2019: 3.2.2.2
Filling placed under a slab (except where the slab is suspended) must comply with the following:
- Filling must be either controlled fill or rolled fill as follows:
- Sand used in controlled fill or rolled fill must not contain any gravel size material and achieve a blow count of 7 or more per 300 mm using the test method described in AS 1289.6.3.3.
- Clay used in controlled fill or rolled fill must be moist during compaction.
-
Controlled fill:
- Sand fill up to 800 mm deep — well compacted in layers not more than 300 mm deep by vibrating plate or vibrating roller.
- Clay fill up to 400 mm deep — well compacted in layers of not more than 150 mm by a mechanical roller.
-
Rolled fill:
- Sand fill up to 600 mm deep — compacted in layers of not more than 300 mm by repeated rolling by an excavator or other suitable mechanical equipment.
- Clay fill up to 300 mm deep — compacted in layers of not more than 150 mm by repeated rolling by an excavator or similar machine.
- A level layer of clean quarry sand must be placed on top of the fill, with a depth of not less than 20 mm.
- A graded stone termite management system complying with Part 3.4 may be substituted for the sand required in (b).
4.2.5
Foundations for footings and slabs
2019: 3.2.2.3
4.2.5
Foundations for footings and slabs
2019: 3.2.2.3
Footings and slabs, including internal and edge beams, must be founded on soil with an allowable bearing pressure as follows:
- Slab panels, load support panels and internal beams — natural soil with an allowable bearing pressure of not less than 50 kPa or controlled fill or rolled fill compacted in accordance with 4.2.4.
- Edge beams connected to the slab — natural soil with an allowable bearing pressure of not less than 50 kPa or controlled fill compacted in accordance with 4.2.4(a)(iii) and extending past the perimeter of the building 1 m with a slope ratio not steeper than 2 horizontal to 1 vertical (see Figure 4.2.5).
- Pad footings, strip footings and edge beams not connected to the slab, must be—
- founded in natural soil with an allowable bearing pressure of not less than 100 kPa; or
- for Class A and S sites they may be founded on controlled sand fill in accordance with 4.2.4(a).
Explanatory information
The foundations of a building are critical to its successful performance. As such, the soil must have the strength or bearing capacity to carry the building load with minimum movement.
The bearing capacity of a soil varies considerably and needs to be determined on a site by site basis. For this to occur, the appropriate people need to be consulted. These people may include a qualified engineer or experienced engineering geologist, or it may be determined by a person with appropriate local knowledge. The minimum bearing capacity (soil strength rating) may depend on the site conditions. The soil may be naturally undisturbed or be disturbed by building work or the like. Where soil is disturbed by building work and the like, the bearing capacity can be dramatically altered. This is typically the case for sloping sites where cut and fill procedures are used. In these situations the soil needs to be consolidated, generally via compaction, to achieve the required bearing capacity.
There are a number of alternatives for working on cut and filled sites. These are described in Figure 4.2.5.
Option 1 of Figure 4.2.5 refers to the controlled fill process which involves the compaction of fill in layers to achieve the bearing capacity described in 4.2.5. The depth of fill for each layer is specified to ensure effective compaction. Fill beyond these depths will need to be installed in accordance with H1D4(1).
Option 2 and 3 of Figure 4.2.5 refer to edge beams that extend through the fill into undisturbed soil which provides the 4.2.5 required bearing capacity. In this situation the fill is essentially only taking the internal slab loads.
4.2.6
Slab edge support on sloping sites
2019: 3.2.2.4
4.2.6
Slab edge support on sloping sites
2019: 3.2.2.4
Footings and slabs installed on the low side of sloping sites must be as follows:
- Slab panels — in accordance with 4.2.5(a).
- Edge beams—
- supported by controlled fill in accordance with 4.2.5(b) (see Figure 4.2.5, Option 1); or
- supported by deepened edge beams or bulk piers designed in accordance with AS 3600 (see Figure 4.2.5, Option 2); or
- deepened (as per AS 2870) to extend into the natural soil level with a bearing capacity in accordance with 4.2.5(b) (see Figure 4.2.5, Option 3); or
- stepped in accordance with AS 2870.
- Edge beams not connected to the slab, pad footings and strip footings — founded in accordance with 4.2.5(c).
- Where an excavation (cut) of the natural ground is used it must be in accordance with Part 3.2.
4.2.7
Stepped footings
2019: 3.2.2.5
4.2.7
Stepped footings
2019: 3.2.2.5
Stepped strip footings must—
- have a base that is horizontal or be sloped at not more than 1:10; or
- be stepped in accordance with one of the methods shown in Figure 4.2.7.
4.2.8
Vapour barriers
2019: 3.2.2.6
4.2.8
Vapour barriers
2019: 3.2.2.6
- 0.2 mm nominal thickness polyethylene film; and
- high impact resistant,
determined in accordance with criteria specified in clause 5.3.3.3 of AS 2870.
- Lap not less than 200 mm at all joints.
- Tape or seal with a close-fitting sleeve around all service penetrations.
- Fully seal where punctured (unless for service penetrations) with additional polyethylene film and tape.
Notes
A range of polyethylene films can be used, including black film and orange film, provided they satisfy the requirements for high impact resistance in accordance with the criteria specified in clause 5.3.3.3 of AS 2870.
Damp-proofing membrane
A continuous damp-proofing membrane must be installed under slab-on-ground construction for all Class 1 buildings and for Class 10 buildings where the slab is continuous with the slab of a Class 1 building as follows—
- Materials: A damp-proofing membrane must be—
- 0.2 mm nominal thickness polyethylene film; and
- high impact resistant with resistance to puncturing and moisture penetration, determined in accordance with criteria specified in clause 5.3.3.3 of AS 2870; and
- branded continuously “AS 2870 Concrete underlay, 0.2 mm High impact resistance” together with the manufacturer’s or distributor’s name, trade mark or code.
- Installation: A damp-proofing membrane must be installed as follows—
- lap not less than 200 mm at all joints; and
- tape or seal with a close fitting sleeve around all service penetrations; and
- fully seal where punctured (unless for service penetrations) with additional polyethylene film and tape.
- The damp-proofing membrane must be placed beneath the slab so that the bottom surface of the slab is entirely underlaid and extends under edge beams to finish at ground level in accordance with Figure 4.2.8.
Damp-proofing membrane
- 0.2 mm nominal thickness polyethylene film; and
- medium impact resistant,
determined in accordance with criteria specified in clause 5.3.3.3 of AS 2870.
- Lap not less than 200 mm at all joints.
- Tape or seal with a close-fitting sleeve around all service penetrations.
- Fully seal where punctured (unless for service penetrations) with additional polyethylene film and tape.
4.2.9
Edge rebates
2019: 3.2.2.7
4.2.9
Edge rebates
2019: 3.2.2.7
Explanatory information
See 4.2.21 for minimum edge beam details. For single skin or framed walls with external cladding, rebates are not required.
4.2.10
Concrete
2019: 3.2.3.1
4.2.10
Concrete
2019: 3.2.3.1
Concrete must comply with the following:
- Concrete must be manufactured to comply with AS 3600; and—
- have a strength at 28 days of not less than 20 MPa (denoted as N20 grade); and
- have a 20 mm maximum nominal aggregate size; and
- have a nominal 100 mm slump.
- Water must not be added to the mix to increase the slump to a value in excess of that specified.
- Concrete must be placed, compacted and cured in accordance with good building practice.
- Concrete in slabs must be adequately compacted, and slab surfaces, including edges, moist cured for 7 days.
- After vertical surfaces are stripped of formwork, slab edges must be finished prior to curing.
- Loading of concrete slabs with stacked materials or building plant must not occur for a minimum of 7 days after pouring although construction of wall frames and setting out brickwork may be undertaken during this period.
- Concrete must not be poured if the air temperature on site exceeds 32ºC unless written instructions from a Professional Engineer are followed.
Explanatory information
- Complete discharge of the concrete from the truck should be made within one and a half hours of initial mixing with water unless a suitable retarder has been specified.
- Compacting concrete by vibration removes air pockets and works the concrete thoroughly around reinforcement, service penetrations etc. and into corners of formwork to increase durability and resistance to termite infestation and salt damp attack. Care should be taken not to over-vibrate. The finishing and curing of slab edges provides an improved edge finish which is resistant to edge dampness.
- Care should be taken when using chemical curing methods, because some products may not be compatible with adhesives used to fix surface finishes to the slab.
Concrete
Concrete must comply with the following:
- Concrete must comply with AS 3600; and—
- have a strength at 28 days of not less than 20 MPa (denoted as N20 grade); and
- have a 20 mm maximum nominal aggregate size; and
- have a nominal 100 mm slump.
- Water must not be added to the mix to increase the slump to a value in excess of that specified.
- Concrete must be placed, compacted and cured in accordance with good building practice.
Explanatory information
- Complete discharge of the concrete from the truck should be made within one and a half hours of initial mixing with water unless a suitable retarder has been specified.
- Compacting concrete by vibration removes air pockets and works the concrete thoroughly around reinforcement, service penetrations etc. and into corners of formwork to increase durability and resistance to termite infestation and salt damp attack. Care should be taken not to over-vibrate. The finishing and curing of slab edges provides an improved edge finish which is resistant to edge dampness.
- Care should be taken when using chemical curing methods, because some products may not be compatible with adhesives used to fix surface finishes to the slab.
4.2.11
Steel reinforcement
2019: 3.2.3.2
4.2.11
Steel reinforcement
2019: 3.2.3.2
- welded wire reinforcing fabric; or
- trench mesh; or
- steel reinforcing bars.
- two strips of 3-L8TM; or
- one strip of 3-L11TM; or
- 3-N12 bars,
not less than 2 m in length and placed at an angle of 45° across the corner such that the centre of the 2 m length is at the location of the internal angle of the slab in accordance with Figure 4.2.11b.
- 40 mm to unprotected ground; and
- 30 mm to a membrane in contact with the ground; and
- 20 mm to an internal surface; and
- 40 mm to external exposure.
- All reinforcement must be firmly fixed in place to prevent it moving during concreting operations.
- Reinforcement must be supported off the ground or the forms by bar chairs made from wire, concrete or plastic.
- When using wire chairs, the minimum concrete cover (see (5)) to the uncoated portion of the chair must be obtained.
- Wire chairs on soft ground or plastic membrane must be placed on flat bases.
- Bar chairs must be spaced at not more than 800 mm centres for steel fabric.
Trench mesh (TM) | Area — mm2 | Reinforcing bar alternative | Trench mesh alternative |
---|---|---|---|
2-L8TM | 91 | 2-N10 or 1-N12 | Not applicable |
3-L8TM | 136 | 2-N10 or 2-N12 | Not applicable |
4-L8TM | 182 | 2-N12 | 2-L11TM |
5-L8TM | 227 | 2-N12 | 3-L11TM |
2-L11TM | 180 | 1-N16 or 2-N12 | 2x2-L8TM |
3-L11TM | 270 | 3-N12 | 2x3-L8TM |
4-L11TM | 360 | 2-N16 | 2x4-L8TM |
2-L12TM | 222 | 2-N12 | 3-L11TM |
3-L12TM | 333 | 3-N12 | 4-L11TM |
4-L12TM | 444 | 4-N12 | 5-L11TM |
Table Notes
- Where necessary, 2 layers of mesh may be used.
- L11TM and L12TM may be replaced by RL1118 and RL1218 mesh respectively.
- L11TM may be replaced by two layers of L8TM.
Reinforcement | Minimum splice | Minimum lap at “T” intersections | Minimum lap at “L” intersections |
---|---|---|---|
Steel reinforcing bars ≤12 mm diameter | 500 mm | Full width across the junction | One outer bar must be bent and continue 500 mm (min) around corner |
Steel reinforcing bars >12 mm to ≤16 mm diameter | 700 mm | Full width across the junction | One outer bar must be bent and continue 500 mm (min) around corner |
Trench mesh | 500 mm | Full width across the junction | Full width across the junction |
Square and rectangular mesh | The two outermost transverse wires of one sheet must overlap the two outermost transverse wires of the other | Not applicable | Not applicable |
Explanatory information: Reinforcement types
Reinforcement types referenced in this clause are described as follows:
- Square mesh is designated in terms of the diameter of each bar and the spacing of consecutive bars. For example, SL62 consists of 6 mm bar at 200 mm spacings.
- Trench mesh is designated in terms of the number of longitudinal bars and the diameter of each bar. For example, 3-L11TM consists of 3 longitudinal bars each of which are 11 mm in diameter.
- Reinforcing bars are designated in terms of the number of bars and the diameter of each bar. For example, 6-N12 consists of 6 bars each of which are 12 mm in diameter.
Explanatory information: Cleaning and placement of reinforcing
In order to obtain a good bond between concrete and reinforcement, the reinforcement should be free of contamination by mud, paint, oils, etc. It is not necessary for the reinforcement to be completely free of rust. Some rusting is beneficial in promoting a good bond as it roughens the surface of the steel. Loose rust, however, must be removed from the reinforcement.
Reinforcement is designed to be in a particular place so as to add strength or to control cracking of the concrete. A displacement from its intended location could make a significant difference to the life or serviceability of the structure.
Supports for fabric reinforcement are provided to prevent the fabric distorting when workers walk on top of it to place the concrete and maintain the correct concrete cover to the fabric.
4.2.12
Footing and slab construction
2019: 3.2.5.1
4.2.12
Footing and slab construction
2019: 3.2.5.1
Footing and slab construction, including size and placement of reinforcement, must be in accordance with the relevant provisions of—
- 4.2.13 for footings for stumps; and
- 4.2.14 for stiffened rafts on Class A, S and M sites; and
- 4.2.15 for strip footing systems on Class A, S and M sites; and
- 4.2.16 for footing slabs on Class A sites; and
- 4.2.17 for footings for single leaf masonry, mixed construction and earth retaining walls; and
- 4.2.18 for footings for fireplaces on Class A and S sites; and
- 4.2.19 for shrinkage control; and
- 4.2.20 for concentrated loads; and
- 4.2.21 for minimum edge beam dimensions; and
- 4.2.22 for recessed areas of slabs.
4.2.13
Stump footing details
2019: 3.2.5.6
4.2.13
Stump footing details
2019: 3.2.5.6
- be designed in accordance with—
- AS 3600; or
- Tables 4.2.13d, 4.2.13e or 4.2.13f; and
- use a minimum 20 MPa concrete as defined in AS 3600.
- designed in accordance with—
- AS 4100; or
- Tables 4.2.13d, 4.2.13e or 4.2.13f; and
- fully enclosed and sealed with a welded top plate; and
- encased in concrete sloping away from the stump and finishing not less than 100 mm above finished ground level; and
- corrosion protected in accordance with Part 6.3.
- AS 1684.2, AS 1684.3, AS 1684.4 or AS 1720.1; or
- Tables 4.2.13d, 4.2.13e or 4.2.13f.
- by a full perimeter masonry base; or
- for concrete stumps — in accordance with AS 3600; or
- for steel stumps — in accordance with AS 4100; or
- for timber stumps — in accordance with AS 1684.2, AS 1684.3, AS 1684.4 or AS 1720.1.
Floor load area (m2) | Dimension (mm) | Roof load area (m2) | ||
---|---|---|---|---|
0 | 6 | 12 | ||
3 | Square pad footing size | 250 x 250 | 300 x 300 | 350 x 350 |
8 | Square pad footing size | 400 x 400 | 400 x 400 | 450 x 450 |
12 | Square pad footing size | 450 x 450 | 500 x 500 | 500 x 500 |
3 | Circular pad footing diameter | 300 | 400 | 400 |
8 | Circular pad footing diameter | 450 | 450 | 600 |
12 | Circular pad footing diameter | 600 | 600 | 600 |
3 | Pad footing depth | 250 | 250 | 250 |
8 | Pad footing depth | 250 | 250 | 250 |
12 | Pad footing depth | 250 | 250 | 250 |
Table Notes
- Load accounted for includes 0.53 kPa permanent floor, 0.92 kN/m permanent wall, 0.4 kPa permanent roof, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations for ULS included are 1.35G and 1.2G + 1.5Q for stumps and G + 0.5Q for pad footings.
- Minimum bearing pressure is 100 kPa for pad footings.
- For pad footings founded on rock, the width or diameter may be reduced by half but not less than 250 mm x 250 mm or 300 mm diameter.
- Stumps are assumed to be braced and simply-supported at both ends with an effective length factor of 1.
- A maximum load eccentricity of length/100 has been accounted for in the stumps.
- A roof load area of “0” must be used for stumps not supporting roof loads.
- The length of wall load allowed for is equal to the square root of the floor area.
Floor load area (m2) | Dimension (mm) | Roof load area (m2) | ||
---|---|---|---|---|
0 | 6 | 12 | ||
3 | Square pad footing size | 300 x 300 | 400 x 400 | 450 x 450 |
8 | Square pad footing size | 450 x 450 | 500 x 500 | 550 x 500 |
12 | Square pad footing size | 500 x 500 | 550 x 550 | 600 x 600 |
3 | Circular pad footing diameter | 400 | 450 | 600 |
8 | Circular pad footing diameter | 600 | 600 | 650 |
12 | Circular pad footing diameter | 650 | 650 | 700 |
3 | Pad footing depth | 250 | 250 | 250 |
8 | Pad footing depth | 250 | 250 | 250 |
12 | Pad footing depth | 250 | 300 | 300 |
Table Notes
- Load accounted for includes 0.98 kPa permanent floor, 0.92 kN/m permanent wall, 0.85 kPa permanent roof, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations for ULS included are 1.35G and 1.2G + 1.5Q for stumps and G + 0.5Q for pad footings.
- Minimum bearing pressure is 100 kPa for pad footings.
- For pad footings founded on rock, the width or diameter may be reduced by half but not less than 250 mm x 250 mm or 300 mm diameter.
- Stumps are assumed to be braced and simply-supported at both ends with an effective length factor of 1.
- A maximum load eccentricity of length/100 has been accounted for in the stumps.
- A roof load area of “0” must be used for stumps not supporting roof loads.
- The length of wall load allowed for is equal to the square root of the floor area.
Floor load area (m2) | Dimension (mm) | Roof load area (m2) | ||
---|---|---|---|---|
0 | 6 | 12 | ||
3 | Square pad footing size | 350 x 350 | 400 x 400 | 450 x 450 |
8 | Square pad footing size | 550 x 550 | 550 x 550 | 600 x 600 |
12 | Square pad footing size | 650 x 650 | 650 x 650 | 700 x 700 |
3 | Circular pad footing diameter | 400 | 450 | 600 |
8 | Circular pad footing diameter | 650 | 650 | 700 |
12 | Circular pad footing diameter | 750 | 750 | 800 |
3 | Pad footing depth | 250 | 250 | 250 |
8 | Pad footing depth | 300 | 300 | 350 |
12 | Pad footing depth | 350 | 350 | 350 |
Table Notes
- Load accounted for includes 0.53 kPa permanent floor, 0.92 kN/m permanent wall, 0.4 kPa permanent roof, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations for ULS included are 1.35G and 1.2G + 1.5Q for stumps and G + 0.5Q for pad footings.
- Minimum bearing pressure is 100 kPa for pad footings.
- For pad footings founded on rock, the width or diameter may be reduced by half but not less than 250 mm x 250 mm or 300 mm diameter.
- Stumps are assumed to be braced and simply-supported at both ends with an effective length factor of 1.
- A maximum load eccentricity of length/100 has been accounted for in the stumps.
- A roof load area of “0” must be used for stumps not supporting roof loads.
- The length of wall load allowed for is equal to the square root of the floor area.
Stump material | Section size (mm) | Floor load area (m2) | Roof load area (m2) | ||
---|---|---|---|---|---|
0 | 6 | 12 | |||
Concrete f’c= 20 MPa | 100 x 100 | 3 | 2500 | 2000 | 1750 |
Concrete f’c = 20 MPa | 100 x 100 | 8 | 1500 | 1500 | 1500 |
Concrete f’c = 20 MPa | 100 x 100 | 12 | 1250 | 1250 | 1250 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 3 | 3000 | 3000 | 3000 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 8 | 3000 | 3000 | 3000 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 12 | 3000 | 3000 | 3000 |
Timber F17 | 100 x 100 | 3 | 3000 | 3000 | 3000 |
Timber F17 | 100 x 100 | 8 | 2500 | 2500 | 2250 |
Timber F17 | 100 x 100 | 12 | 2250 | 2000 | 2000 |
Timber F14 | 100 x 100 | 3 | 3000 | 3000 | 2500 |
Timber F14 | 100 x 100 | 8 | 2250 | 2000 | 1750 |
Timber F14 | 100 x 100 | 12 | 1750 | 1500 | 1500 |
Timber F11 | 100 x 100 | 3 | 3000 | 2500 | 2250 |
Timber F11 | 100 x 100 | 8 | 2000 | 1750 | 1750 |
Timber F11 | 100 x 100 | 12 | 1500 | 1500 | 1250 |
Timber F8 | 100 x 100 | 3 | 3000 | 2500 | 2000 |
Timber F8 | 100 x 100 | 8 | 1750 | 1500 | 1250 |
Timber F8 | 100 x 100 | 12 | 1250 | 1000 | 750 |
Timber F7 | 100 x 100 | 3 | 2500 | 2250 | 1750 |
Timber F7 | 100 x 100 | 8 | 1500 | 1250 | 750 |
Timber F7 | 100 x 100 | 12 | 750 | – | – |
Timber F5 | 100 x 100 | 3 | 2500 | 2000 | 1500 |
Timber F5 | 100 x 100 | 8 | 1250 | 750 | – |
Timber F5 | 100 x 100 | 12 | – | – | – |
Table Notes
- Load accounted for includes 0.53 kPa permanent floor, 0.92 kN/m permanent wall, 0.4 kPa permanent roof, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations for ULS included are 1.35G and 1.2G + 1.5Q for stumps and G + 0.5Q for pad footings.
- Minimum bearing pressure is 100 kPa for pad footings.
- Stumps are assumed to be braced and simply-supported at both ends with an effective length factor of 1.
- A maximum load eccentricity of length/100 has been accounted for in the stumps.
- A roof load area of “0” must be used for stumps not supporting roof loads.
- The length of wall load allowed for is equal to the square root of the floor area.
Stump material | Section size (mm) | Floor load area (m2) | Roof load area (m2) | ||
---|---|---|---|---|---|
0 | 6 | 12 | |||
Concrete f’c = 20 MPa | 100 x 100 | 3 | 2250 | 1750 | 1500 |
Concrete f’c = 20 MPa | 100 x 100 | 8 | 1500 | 1250 | 1250 |
Concrete f’c = 20 MPa | 100 x 100 | 12 | 1250 | 1250 | 750 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 3 | 3000 | 3000 | 3000 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 8 | 3000 | 3000 | 3000 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 12 | 3000 | 3000 | 3000 |
Timber F17 | 100 x 100 | 3 | 3000 | 3000 | 2500 |
Timber F17 | 100 x 100 | 8 | 2500 | 2250 | 2000 |
Timber F17 | 100 x 100 | 12 | 2000 | 2000 | 1750 |
Timber F14 | 100 x 100 | 3 | 3000 | 2500 | 2000 |
Timber F14 | 100 x 100 | 8 | 2000 | 1750 | 1500 |
Timber F14 | 100 x 100 | 12 | 1500 | 1250 | 1000 |
Timber F11 | 100 x 100 | 3 | 3000 | 2250 | 2000 |
Timber F11 | 100 x 100 | 8 | 1750 | 1500 | 1250 |
Timber F11 | 100 x 100 | 12 | 1250 | 1000 | 750 |
Timber F8 | 100 x 100 | 3 | 2500 | 2000 | 1750 |
Timber F8 | 100 x 100 | 8 | 1500 | 1250 | 1000 |
Timber F8 | 100 x 100 | 12 | 1000 | 500 | – |
Timber F7 | 100 x 100 | 3 | 2500 | 1750 | 1250 |
Timber F7 | 100 x 100 | 8 | 1250 | 750 | – |
Timber F7 | 100 x 100 | 12 | – | – | – |
Timber F5 | 100 x 100 | 3 | 2250 | 1500 | 1000 |
Timber F5 | 100 x 100 | 8 | 750 | – | – |
Timber F5 | 100 x 100 | 12 | – | – | – |
Table Notes
- Load accounted for includes 0.98 kPa permanent floor, 0.92 kN/m permanent wall, 0.85 kPa permanent roof, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations for ULS included are 1.35G and 1.2G + 1.5Q for stumps and G + 0.5Q for pad footings.
- Minimum bearing pressure is 100 kPa for pad footings.
- Stumps are assumed to be braced and simply-supported at both ends with an effective length factor of 1.
- A maximum load eccentricity of length/100 has been accounted for in the stumps.
- A roof load area of “0” must be used for stumps not supporting roof loads.
- The length of wall load allowed for is equal to the square root of the floor area.
Stump material | Section size (mm) | Floor load area (m2) | Roof load area (m2) | ||
---|---|---|---|---|---|
0 | 6 | 12 | |||
Concrete f’c = 20 MPa | 100 x 100 | 3 | 1750 | 1500 | 1500 |
Concrete f’c = 20 MPa | 100 x 100 | 8 | 1250 | 1000 | 750 |
Concrete f’c = 20 MPa | 100 x 100 | 12 | – | – | – |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 3 | 3000 | 3000 | 3000 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 8 | 3000 | 3000 | 3000 |
Steel fy = 350 MPa | 100 x 100 x 2.0 | 12 | 3000 | 2750 | 2500 |
Timber F17 | 100 x 100 | 3 | 3000 | 2500 | 2500 |
Timber F17 | 100 x 100 | 8 | 1750 | 1750 | 1500 |
Timber F17 | 100 x 100 | 12 | 1250 | 1250 | 1250 |
Timber F14 | 100 x 100 | 3 | 2500 | 2250 | 2000 |
Timber F14 | 100 x 100 | 8 | 1250 | 1250 | 1000 |
Timber F14 | 100 x 100 | 12 | 750 | 500 | 500 |
Timber F11 | 100 x 100 | 3 | 2250 | 2000 | 1750 |
Timber F11 | 100 x 100 | 8 | 1000 | 1000 | 750 |
Timber F11 | 100 x 100 | 12 | – | – | – |
Timber F8 | 100 x 100 | 3 | 2000 | 1750 | 1500 |
Timber F8 | 100 x 100 | 8 | 500 | 500 | – |
Timber F8 | 100 x 100 | 12 | – | – | – |
Timber F7 | 100 x 100 | 3 | 1750 | 1500 | 1250 |
Timber F7 | 100 x 100 | 8 | – | – | – |
Timber F7 | 100 x 100 | 12 | – | – | – |
Timber F5 | 100 x 100 | 3 | 1500 | 1000 | 750 |
Timber F5 | 100 x 100 | 8 | – | – | – |
Timber F5 | 100 x 100 | 12 | – | – | – |
Table Notes
- Load accounted for includes 0.53 kPa permanent floor, 0.92 kN/m permanent wall, 0.4 kPa permanent roof, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations for ULS included are 1.35G and 1.2G + 1.5Q for stumps and G + 0.5Q for pad footings.
- Minimum bearing pressure is 100 kPa for pad footings.
- Stumps are assumed to be braced and simply-supported at both ends with an effective length factor of 1.
- A maximum load eccentricity of length/100 has been accounted for in the stumps.
- A roof load area of “0” must be used for stumps not supporting roof loads.
- The length of wall load allowed for is equal to the square root of the floor area.
Effective supported areas (m2) | Width of square pad (mm) | Width of circular pad (mm) | Thickness (t) (mm) | Depth (mm) |
---|---|---|---|---|
10 | 400 | 500 | 200 | 400 |
20 | 500 | 600 | 200 | 400 |
30 | 600 | 750 | 250 | 400 |
Table Notes
- The effective area supported by a pad footing is the sum of—
- the supported floor area; and
- the supported roof area (if applicable); and
- half the supported wall area in elevation (if applicable).
- The width or diameter can be reduced to one half the above footings on rock.
- The pad footings must be constructed in concrete.
- Pad footing sizes must also apply to footings supporting roof and floor loads only.
- The foundation must provide an allowable bearing pressure of not less than 100 kPa.
- The excavation must be backfilled with manually rodded tamped soil, or the footing thickness shall be increased by 50 mm.
- Where stump pad footings provide resistance to horizontal or uplift forces, the minimum size of the footing must comply with AS 2870.
- Braced stumps must comply with 4.2.13(5).
- For masonry piers, strip footings complying with 4.2.15 for masonry can be used in lieu of pad footings.
4.2.14
Stiffened rafts Class A, S and M sites
New for 2022
4.2.14
Stiffened rafts Class A, S and M sites
New for 2022
Footing and stiffened raft slabs must comply with—
- For Class A and S sites — Tables 4.2.14a, 4.2.14b and Figure 4.2.14a; and
- For Class M sites — Table 4.2.14c and Figure 4.2.14b.
Type of construction | Depth (D) (mm) | Bottom reinf. | Max. spacing c/l to c/l | Slab fabric |
---|---|---|---|---|
Clad frame | 300 | 3-L8TM | N/A | SL72 |
Articulated masonry veneer | 300 | 3-L8TM | N/A | SL72 |
Masonry veneer | 300 | 3-L8TM | N/A | SL72 |
Articulated full masonry | 400 | 3-L8TM | N/A | SL72 |
Full masonry | 400 | 3-L8TM | N/A | SL72 |
Table Notes
- Internal and external edge beams must be arranged to form an integral structural grid (see clauses 5.3.8 and 5.3.9 of AS 2870).
- A 10% increase in spacings is permitted where the spacing in the other direction is 20% less than that specified.
- Where external beams are wider than 300 mm, an extra bottom bar or equivalent of the same bar size is required for each 100 mm additional width.
- Where a reinforced single leaf masonry wall is constructed directly above and structurally connected to a concrete edge beam, the beam may be reduced to 300 mm wide by 300 mm deep and reinforced with 3–L8TM reinforcement.
- Alternative reinforcement sizes must comply with AS 2870.
- Internal beam details and spacings must comply with Figure 4.2.14a or Figure 4.2.14b.
Type of construction | Depth (D) (mm) | Bottom reinf. | Max. spacing c/l to c/l | Slab fabric |
---|---|---|---|---|
Clad frame | 300 | 3-L8TM | N/A | SL72 |
Articulated masonry veneer | 300 | 3-L8TM | N/A | SL72 |
Masonry veneer | 300 | 3-L11TM | N/A | SL72 |
Articulated full masonry | 450 | 3-L11TM | N/A | SL72 |
Full masonry | 450 | 3-N16 | 5.0 (m) Note 2 | SL82 |
Table Notes
- Internal and external edge beams must be arranged to form an integral structural grid (see clauses 5.3.8 and 5.3.9 of AS 2870).
- A 10% increase in spacings is permitted where the spacing in the other direction is 20% less than that specified.
- Where external beams are wider than 300 mm, an extra bottom bar or equivalent of the same bar size is required for each 100 mm additional width.
- Where a reinforced single leaf masonry wall is constructed directly above and structurally connected to a concrete edge beam, the beam may be reduced to 300 mm wide by 300 mm deep and reinforced with 3–L8TM reinforcement.
- Alternative reinforcement sizes must comply with AS 2870.
- Internal beam details and spacings must comply with Figure 4.2.14a or Figure 4.2.14b.
Type of construction | Depth (D) (mm) | Bottom reinf. | Max. spacing c/l to c/l | Slab mesh |
---|---|---|---|---|
Clad frame | 300 | 3-L11TM | 6.0Note 2 | SL72 |
Articulated masonry veneer | 400 | 3-L11TM | 6.0Note 2 | SL72 |
Masonry veneer | 400 | 3-L11TM | 5.0Note 2 | SL72 |
Articulated full masonry | 500 | 3-L12TM | 4.0 | SL82 |
Full masonry | 850 | 3-N16 | 4.0 | SL92 |
Table Notes
- Internal and external edge beams must be arranged to form an integral structural grid (see clauses 5.3.8 and 5.3.9 of AS 2870).
- A 10% increase in spacings is permitted where the spacing in the other direction is 20% less than that specified.
- Where external beams are wider than 300 mm, an extra bottom bar or equivalent of the same bar size is required for each 100 mm additional width.
- Where a reinforced single leaf masonry wall is constructed directly above and structurally connected to a concrete edge beam, the beam may be reduced to 300 mm wide by 300 mm deep and reinforced with 3–L8TM reinforcement.
- Alternative reinforcement sizes must comply with AS 2870.
- Internal beam details and spacings must comply with Figure 4.2.14b.
4.2.15
Strip footings Class A, S and M sites
New for 2022
4.2.15
Strip footings Class A, S and M sites
New for 2022
Strip footings for Class A, S and M sites must comply with—
- for Class A and S sites — Tables 4.2.15a, 4.2.15b and Figure 4.2.15a; and
- for Class M sites — Table 4.2.15c and Figure 4.2.15b.
Type of construction | D (mm) | B (mm) | Reinforcement (top and bottom) |
---|---|---|---|
Clad frame | 300 | 300 | 3–L8TM |
Articulated masonry veneer | 300 | 300 | 3–L8TM |
Masonry veneer | 300 | 300 | 3–L8TM |
Articulated full masonry | 300 | 400 | 4–L8TM |
Full masonry | 300 | 400 | 4–L8TM |
Table Notes
- All masonry walls must be supported on strip footings.
- Internal strip footings must be of the same proportions as the external footings and run from external footing to external footing. ‘Side slip joints’ consisting of a double layer of polyethylene must be provided at the sides of the footing only.
- Infill floors may be concrete slabs, brick paving, stone flags or compacted and stabilised earth. For concrete slab infill panels, mesh may be required to control shrinkage in slab panels and around openings or restrained regions. Concrete infill slabs must use a minimum of SL62 mesh to control shrinkage (see also 4.2.19).
- Where footings are wider than the specified width, an extra bottom bar or equivalent of the same bar size is required for each 100 mm additional width. If strip footings deeper than those required are used, the reinforcement must be increased to match that specified for the deepened proportions.
- The measurement of Df is greater or equal to D plus 75 mm.
- Alternative reinforcing sizes must comply with AS 2870.
Type of construction | D (mm) | B (mm) | Reinforcement (top and bottom) |
---|---|---|---|
Clad frame | 400 | 300 | 3–L8TM |
Articulated masonry veneer | 400 | 300 | 3–L8TM |
Masonry veneer | 400 | 300 | 3–L8TM |
Articulated full masonry | 400 | 400 | 4–L11TM |
Full masonry | 500 | 400 | 4–L11TM |
Table Notes
- All masonry walls must be supported on strip footings.
- Internal strip footings must be of the same proportions as the external footings and run from external footing to external footing. ‘Side slip joints’ consisting of a double layer of polyethylene must be provided at the sides of the footing only.
- Infill floors may be concrete slabs, brick paving, stone flags or compacted and stabilised earth. For concrete slab infill panels, mesh may be required to control shrinkage in slab panels and around openings or restrained regions. Concrete infill slabs must use a minimum of SL62 mesh to control shrinkage (see also 4.2.19).
- Where footings are wider than the specified width, an extra bottom bar or equivalent of the same bar size is required for each 100 mm additional width. If strip footings deeper than those required are used, the reinforcement must be increased to match that specified for the deepened proportions.
- The measurement of Df is greater or equal to D plus 75 mm.
- Alternative reinforcing sizes must comply with AS 2870.
Type of construction | D (mm) | B (mm) | Reinforcement (top and bottom) |
---|---|---|---|
Clad frame | 400 | 300 | 3-L11TM |
Articulated masonry veneer | 450 | 300 | 3-L11TM |
Masonry veneer | 500 | 300 | 3-L12TM |
Articulated full masonry | 600 | 400 | 4-L12TM |
Full masonry | 900 Note 2 | 400 | 4-L12TM |
Table Notes
- All masonry walls must be supported on strip footings.
- For beams 700 mm or deeper, as specified in the table above, internal footings must be provided at no more than 6 m centres and at re-entrant corners to continue footings to the opposite external footing. Internal strip footings must be of the same proportions as the external footings and run from external footing to external footing. ‘Side slip joints’ consisting of a double layer of polyethylene must be provided at the sides of the footing only.
- Infill floors must only be used for Class A and S sites.
- Where footings are wider than the specified width, an extra bottom bar or equivalent of the same bar size is required for each 100 mm additional width. If strip footings deeper than those required are used, the reinforcement must be increased to match that specified for the deepened proportions.
- The measurement of Df is greater or equal to D plus 75 mm.
- Alternative reinforcing sizes must comply with AS 2870.
- For Class M articulated full masonry and full masonry, internal strip footings must be of the same proportions as the external footing and run from external footing to external footing.
4.2.16
Footing slabs for Class A sites
New for 2022
4.2.16
Footing slabs for Class A sites
New for 2022
Footing slabs for Class A sites supporting the following external wall types must comply with Figure 4.2.16:
- Clad frame.
- Articulated masonry.
- Masonry veneer.
- Articulated full masonry.
- Full masonry.
4.2.17
Footings for single leaf masonry, mixed construction and earth wall construction
2019: 3.2.5.2
4.2.17
Footings for single leaf masonry, mixed construction and earth wall construction
2019: 3.2.5.2
Footings supporting the following external wall types must comply with the equivalent wall construction set out in Tables 4.2.17a, 4.2.17b and 4.2.17c:
- Single leaf masonry.
- Mixed construction.
- Earth wall structures.
Actual construction: external walls | Actual construction: internal walls | Equivalent wall construction |
---|---|---|
Reinforced single leaf masonry | Articulated masonry on Class A and Class S sites, or framed | Articulated masonry veneer |
Reinforced single leaf masonry | Articulated masonry or reinforced single leaf masonry | Masonry veneer |
Articulated single leaf masonry | Articulated masonry | Articulated full masonry |
Actual construction: external walls | Actual construction: internal walls | Equivalent wall construction |
---|---|---|
Full masonry | Framed | Articulated full masonry |
Articulated full masonry | Framed | Masonry veneer |
Actual construction: external walls | Actual construction: internal walls | Equivalent wall construction |
---|---|---|
Infill panels of earth wall construction | Framed earth wall construction | Articulated masonry veneer |
Loadbearing earth wall construction | Loadbearing earth wall construction | Articulated full masonry |
Explanatory information
Tables 4.2.17a, 4.2.17b and 4.2.17c provide solutions for footings that are equivalent to those supporting a wall type that may be different to the actual type included in design documentation. The equivalent wall construction in the right-hand column of each of these tables recognises the types of footing systems suitable to support the actual external wall and internal wall types that may not have a specific solution for supporting footings.
4.2.18
Footings for fireplaces on Class A and S sites
2019: 3.2.5.5
4.2.18
Footings for fireplaces on Class A and S sites
2019: 3.2.5.5
- 150 mm thick for single storey (one trafficable floor and a wall height not more than 4.2 m) construction; and
- 200 mm thick for 2 storey (two trafficable floors and a wall height not more than 8 m) construction; and
- reinforced top and bottom with SL72 mesh; and
- extending 300 mm past the edges of the masonry except for any edge flush with the outer wall.
4.2.19
Shrinkage control
2019: 3.2.5.3
4.2.19
Shrinkage control
2019: 3.2.5.3
Where brittle floor coverings, such as ceramic tiles, are to be used over an area greater than 16 m2, one of the following additional measures must be taken to control the effect of shrinkage cracking—
- the amount of shrinkage reinforcement (steel reinforcement mesh in the slab panel) must be—
- increased to SL92 or equivalent throughout the affected slab area; or
- reinforced top and bottom with sheets of slab mesh throughout the affected slab area; or
- the bedding system for brittle coverings must be selected on the basis of the expected slab movement and the characteristics of the floor covering (including the use of expansion joints etc.); or
- the placement of floor covering must be delayed for not less than 3 months after the concrete has been poured.
4.2.20
Concentrated loads
New for 2022
4.2.20
Concentrated loads
New for 2022
Where a footing or slab supports a concentrated load from a structural steel column, localised thickening must—
- be provided in accordance with—
- for tiled floor and tiled roof, Tables 4.2.20a, 4.2.20b or 4.2.20c; or
- for timber floor and metal roof, Tables 4.2.20d, 4.2.20e or 4.2.20f; and
- be centred under the structural steel column; and
- have SL72 reinforcement with a minimum 50 mm of concrete cover (see Figure 4.2.20).
Localised thickening | Maximum floor load area (m2) | ||
---|---|---|---|
4 | 10 | 16 | |
Square thickening size (mm) | 450 x 450 | 650 x 650 | 850 x 850 |
Thickening depth (mm) | 250 | 350 | 400 |
Table Notes
- Load accounted for includes 0.98 kPa permanent tiled floor, 0.85 kPa permanent tiled roof, 1.16 kN/m permanent wall, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations included are G + 0.5Q for ULS.
- Minimum bearing pressure is 100 kPa for pad footings.
- A roof load area of “0” must be used for footings not supporting roof loads.
- The length of wall allowed for is equal to the square root of the floor area.
Localised thickening | Maximum floor load area (m2) | ||
---|---|---|---|
4 | 10 | 16 | |
Square thickening size (mm) | 650 x 650 | 800 x 800 | 950 x 950 |
Thickening depth (mm) | 350 | 400 | 450 |
Table Notes
- Load accounted for includes 0.98 kPa permanent tiled floor, 0.85 kPa permanent tiled roof, 1.16 kN/m permanent wall, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations included are G + 0.5Q for ULS.
- Minimum bearing pressure is 1000 kPa for pad footings.
- The length of wall allowed for is equal to the square root of the floor area.
Localised thickening | Maximum floor load area (m2) | ||
---|---|---|---|
4 | 10 | 16 | |
Square thickening size (mm) | 750 x 750 | 900 x 900 | 1000 x 1000 |
Thickening depth (mm) | 400 | 450 | 500 |
Table Notes
- Load accounted for includes 0.98 kPa permanent tiled floor, 0.85 kPa permanent tiled roof, 1.16 kN/m permanent wall, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations included are G + 0.5Q for ULS.
- Minimum bearing pressure is 1000 kPa for pad footings.
- The length of wall allowed for is equal to the square root of the floor area.
Localised thickening | Maximum floor load area (m2) | ||
---|---|---|---|
4 | 10 | 16 | |
Square thickening size (mm) | 400 x 400 | 600 x 600 | 750 x 750 |
Thickening depth (mm) | 250 | 300 | 350 |
Table Notes
- Load accounted for includes 0.53 kPa permanent timber floor, 0.4 kPa permanent metal roof, 1.16 kN/m permanent wall, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations included are G + 0.5Q for ULS.
- Minimum bearing pressure is 1000 kPa for pad footings.
- A roof load area of “0” must be used for footings not supporting roof loads.
- The length of wall allowed for is equal to the square root of the floor area.
Localised thickening | Maximum floor load area (m2) | ||
---|---|---|---|
4 | 10 | 16 | |
Square thickening size (mm) | 500 x 500 | 700 x 700 | 800 x 800 |
Thickening depth (mm) | 300 | 350 | 400 |
Table Notes
- Load accounted for includes 0.53 kPa permanent timber floor, 0.4 kPa permanent metal roof, 1.16 kN/m permanent wall, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations included are G + 0.5Q for ULS.
- Minimum bearing pressure is 1000 kPa for pad footings.
- The length of wall allowed for is equal to the square root of the floor area.
Localised thickening | Maximum floor load area (m2) | ||
---|---|---|---|
4 | 10 | 16 | |
Square thickening size (mm) | 600 x 600 | 750 x 750 | 850 x 850 |
Thickening depth (mm) | 300 | 400 | 450 |
Table Notes
- Load accounted for includes 0.53 kPa permanent timber floor, 0.4 kPa permanent metal roof, 1.16 kN/m permanent wall, permanent member self-weight, 1.5 kPa or 1.1 kN imposed floor and 0.25 kPa imposed roof.
- Load combinations included are G + 0.5Q for ULS.
- Minimum bearing pressure is 1000 kPa for pad footings.
- The length of wall allowed for is equal to the square root of the floor area.
4.2.21
Minimum edge beam dimensions
2019: 3.2.5.4
4.2.21
Minimum edge beam dimensions
2019: 3.2.5.4
For footing slabs, the width of the edge beam at the base of the rebate must not be less than 200 mm, except that if R10 or N10 ties at 900 mm spacing (or equivalent) are provided to resist vertical forces, the width of the edge beam at the base of the rebate can be reduced to 150 mm.
4.2.22
Recessed areas of slabs
New for 2022
4.2.22
Recessed areas of slabs
New for 2022
- For recess depths less than or equal to half the nominal slab thickness, the reinforcing mesh must have a minimum lap length of 400 mm measured from the inside face of the recess (see Figure 4.2.22a).
- For recess depths greater than half the nominal slab thickness (see Figure 4.2.22b)—
- top reinforcing mesh must overlap the bottom reinforcing mesh by not less than 400 mm; and
- bottom reinforcing mesh must be two layers of SL72.