Strip footings: continuous concrete footings for load-bearing walls
Strip footing dimensions, trench mesh, concrete grade, and articulation joint rules for Australian residential builders. AS 2870 and Housing Provisions 4.2.15 verified.
Ask Chalkline about this →TL;DR
Strip footings are continuous concrete beams cast in a trench under every load-bearing wall: the primary footing type for masonry construction on Class A, S, and M sites per AS 2870:2011 and ABCB Housing Provisions Part 4.2. Minimum depth runs from 300 mm on Class A for clad frame up to 900 mm on Class M for full masonry. The wall construction type (clad frame, masonry veneer, full masonry) determines the table you use: full masonry loads are about double clad frame loads, and the footings reflect that. Trench mesh laps a minimum of 500 mm at joins. H, E, and P sites fall outside the Housing Provisions tables: they need a structural engineer working directly to AS 2870.
When you do this
Strip footings are formed and poured after:
- Bulk earthworks and site cut are complete
- Soil report has confirmed the site class
- Engineer’s drawings (for H, E, P sites) or DTS table selections are confirmed
- Subgrade is prepared and inspected at the required hold point
Strip footings precede slab-on-ground work. On a project with a suspended slab or a stiffened raft, the strip footing IS the edge beam system. On masonry veneer or full masonry houses with a concrete floor, the strip footing is a separate discrete element under each leaf of masonry.
Who’s involved
| Role | Responsibility |
|---|---|
| Structural engineer | Required for H, E, P sites; provides drawings and concrete spec |
| Geotechnical engineer | Soil report, site classification |
| Builder | Programme, hold point management, concrete ordering |
| Concretor | Trench preparation, formwork, reo placement, concrete pour and finish |
| Building certifier | Pre-pour inspection hold point; cannot pour until cleared |
Steps
-
Confirm site class from soil report. The site class is on the geotech report. Class A, S, and M are within the Housing Provisions DTS tables. Class H1, H2, E, and P require engineering under AS 2870 directly. Never pick a DTS table without a confirmed soil report on a reactive clay site.
-
Select the footing dimensions from the correct table. For Class A, S, and M sites, use the Housing Provisions Part 4.2.15 tables matching your site class and wall construction type (see table below). For H, E, P sites, use the engineer’s drawings.
-
Excavate trenches to depth. Set out trench lines from the building grid. Excavate to the minimum depth from the table, measured from natural or finished subgrade. The base of the trench must be on stable, undisturbed soil. Soft spots or fill require engineering sign-off before proceeding.
-
Prepare subgrade. Compact the trench base. On reactive sites, minimise the time the trench is left open: open trenches on clay absorb moisture and degrade bearing capacity. Pour within 24 to 48 hours of excavation on Class M sites where possible.
-
Set reinforcement. Place trench mesh or bar as specified. Minimum concrete cover: 40 mm to unprotected ground, 30 mm to a membrane (Housing Provisions clause 4.2.11, verified 2026-05-10). Lap trench mesh 500 mm minimum at joins per Table 4.2.11b of the Housing Provisions (verified 2026-05-10, ABCB Housing Provisions Part 4.2). Use bar chairs to maintain cover to the base; do not rest reo on loose soil or rubble.
-
Install side slip joints at articulation locations. At any location where an articulation joint in the masonry wall above aligns with the footing run, install a side slip joint: a double layer of polyethylene sheeting at the sides of the footing (Housing Provisions Table notes 4.2.15a/b/c, verified 2026-05-10). The side slip joint allows the footing to accommodate minor differential movement without constraint cracking. Do not place the polyethylene under the full footing base; it goes at the sides only.
-
Book the pre-pour inspection. The certifier must inspect the trench, subgrade, reo placement, and cover before the concrete truck arrives. This is a mandatory hold point. Do not pour without clearance.
-
Place concrete. Minimum N20 grade (20 MPa at 28 days), maximum 20 mm aggregate, nominal 100 mm slump per Housing Provisions clause 4.2.10 (verified 2026-05-10, ABCB Housing Provisions Part 4.2). Do not add water to the mix on site. Vibrate to consolidate around reinforcement. Strike off level.
-
Cure. Cure per the concrete specification: minimum 7 days moist curing. On hot days, cover with hessian and water or curing membrane. Do not allow the footing to dry out rapidly; this causes surface crazing that can propagate into structural cracking on reactive sites.
-
Install DPC before brickwork. A damp-proof course is placed on top of the cured footing before the first brick course. The DPC must be at least 150 mm above adjacent finished ground level per Housing Provisions Part 5.7.3.
Tolerances and acceptance
| Aspect | Requirement | Source |
|---|---|---|
| Footing depth (D) | Meets the minimum per site class and construction type table (see below) | Housing Provisions 4.2.15 |
| Footing width (B) | Meets the minimum per table | Housing Provisions 4.2.15 |
| Concrete grade | N20 minimum (20 MPa at 28 days) | Housing Provisions 4.2.10 |
| Trench mesh lap | 500 mm minimum at all splices | Housing Provisions Table 4.2.11b |
| Concrete cover to ground | 40 mm unprotected; 30 mm to membrane | Housing Provisions 4.2.11 |
| Level | Footing level within tolerance stated on engineer’s drawings or within +/- 5 mm across run where engineer not specified | Workmanship standard |
Workmanship tolerances for finished footing level relative to datum are subject to HIA Guide values. Per current HIA Guide to Materials and Workmanship pending HIA member access. [HIA-073]
Footing dimensions: Housing Provisions 4.2.15 tables
All dimensions verified 2026-05-10 against ABCB Housing Provisions Part 4.2.
Class A sites (Table 4.2.15a)
| Construction type | Min. depth D (mm) | Min. width B (mm) | Trench mesh (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 | 3-L8TM |
| Full masonry | 300 | 400 | 3-L8TM |
Class S sites (Table 4.2.15b)
| Construction type | Min. depth D (mm) | Min. width B (mm) | Trench mesh (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 |
Class M sites (Table 4.2.15c)
| Construction type | Min. depth D (mm) | Min. width B (mm) | Trench mesh (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 | 3-L12TM |
| Full masonry | 900 | 400 | 4-L12TM |
Notes:
- Depth D is measured from the underside of the footing to the underside of the DPC or floor slab, not from finished ground.
- Internal footings must be the same proportions as external footings and must run continuously from external footing to external footing (Housing Provisions 4.2.15 table notes).
- Side slip joints (double polyethylene at footing sides) are required at articulation joint locations in the masonry above.
- For H1, H2, E, and P sites: these tables do not apply. Engineering under AS 2870 is required.
Construction types: what they mean on site
| Term | What it means |
|---|---|
| Clad frame | Timber or steel frame with non-masonry external cladding (weatherboard, fibre cement sheet, metal cladding). Lower wall loads. |
| Masonry veneer | Loadbearing frame clad with a single outer leaf of brick or block. Frame carries the floor/roof; masonry is non-structural cladding. The footing under the masonry leaf is a strip footing; the frame may sit on a separate pad or slab element. |
| Articulated masonry veneer | As above, but with articulation joints at maximum centres per AS 3700:2018 and NCC Housing Provisions Part 5.6.8, allowing each panel of masonry to move independently. Articulated walls attract less restraint load; deeper footings not needed. |
| Full masonry | Double-leaf external walls: masonry carries the structural load. Internal walls also masonry. The footing must carry significantly higher loads. Full masonry on Class M requires a 900 mm deep footing. |
| Articulated full masonry | Full masonry with articulation joints at the required centres. Reduces footing depth requirement versus unjointed full masonry. |
Common holds
| Hold | Why it happens | Fix |
|---|---|---|
| Soft spot at trench base | Clay moisture, undetected fill, tree root zone | Deepen trench to competent material or get engineering sign-off for treatment |
| Reo failing cover inspection | Bar chairs missed, mesh sagging, soil contaminating cover | Re-set and re-inspect before pour |
| Wrong construction type selected from table | Builder uses clad frame table for masonry veneer construction | Use correct table row; add depth if already excavated to wrong depth |
| Concrete ordered at wrong grade | Sub-N20 mix specified | Do not pour; reorder correct grade |
| No DPC height above ground | Ground level raised after footing poured (paving, landscaping, fill) | DPC must be minimum 150 mm above finished adjacent ground; re-evaluate if landscaping changes the level post-pour |
Documents needed
- Soil report (confirming site class)
- Engineer’s drawings (mandatory for H, E, P sites; advisory for Class M where engineer is engaged)
- Concrete delivery docket (confirming N20 grade and batch details)
- Inspection sign-off from certifier (pre-pour hold point)
- Concrete test cylinders or NATA slip (where specified by engineer)
References
- Australian Building Codes Board, ABCB Housing Provisions 2022, Part 4.2 Footings, slabs and associated elements. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/4-footings-and-slabs/part-42-footings-slabs-and-associated-elements (verified 2026-05-10).
- Australian Building Codes Board, NCC 2022 Volume Two, Part H1 Structure, Clause H1D4. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/h-class-1-and-10-buildings/part-h1-structure (verified 2026-05-10).
- Standards Australia, AS 2870:2011 Residential slabs and footings. https://store.standards.org.au/product/as-2870-2011 (verified 2026-05-10, paywalled).
Related
- AS 2870:2011, the Australian Standard for residential slab and footing design, covering all site classes
- Slab on ground construction, the full slab sequence from subgrade through to pre-pour inspection and curing
- Footing, plain-English definition
- Trench mesh, the reinforcement product used in strip footings
- Damp-proof course, installed on the cured footing before brickwork
- Articulation joint, the masonry control joint that triggers side slip joints in the footing below
- Reo (steel reinforcement), bar and mesh specifications for concrete work
See also
- Soil report (geotech), what the soil report contains and how to read the site class
- Stiffened raft slab, the most common residential slab system, which incorporates strip-footing-style edge beams
- Masonry veneer, explains the wall construction type behind the masonry veneer row in the tables
- Cavity masonry, double-leaf masonry wall type
- NCC 2022 Volume Two, where H1D4 sits and how the Housing Provisions are called up
- AS 3700:2018 masonry structures, masonry standard setting articulation joint spacing above strip footings
- Waffle pod slab, the reactive-site alternative on H1/H2 sites where strip footings alone are insufficient
Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency: confirm Housing Provisions Part 4.2.15 tables remain current at ABCB website.