Pad footing
Pad footing is an isolated reinforced concrete pad under a single concentrated load: a post, pier or column. Sized to bearing capacity under AS 2870.
Ask Chalkline about this →A pad footing is an isolated reinforced-concrete pad cast under a single concentrated load such as a column, a deck post, a verandah pier, or a stump on a pier-and-beam floor system. The pad spreads the point load over an area of bearing soil large enough that the soil pressure remains within its allowable capacity. Pad footings are designed under AS 2870:2011, Residential slabs and footings (verified 2026-05-15) for site classifications A, S and M, or under site-specific engineering for higher reactivity (H1, H2, P) and for higher-load applications.
Typical residential dimensions (Class A or S site, deck post or verandah pier, normal load):
| Element | Typical value |
|---|---|
| Plan size | 450 x 450 mm to 600 x 600 mm |
| Depth | 450 to 600 mm |
| Reinforcement | Trench mesh top and bottom, or N12 bar cage where engineered |
| Concrete strength | N20 (most residential), N25 for higher loads |
| Cover to reinforcement | 50 mm bottom, 40 mm sides |
Heavier loads (a steel UB column from a goalpost portal, a multi-storey corner post) require pad sizes set by the structural engineer, not from AS 2870 tables.
Where pad footings are used in residential construction:
- Pier-and-beam floors: a pad under each pier.
- Detached deck or pergola posts: a pad below each post.
- Carport columns.
- Verandah posts on a re-stumping job.
- Internal columns under a beam supporting a wide span (alterations and additions).
- Stair-landing post supports on split-level builds.
Pad vs strip vs raft footings:
- A strip footing is a continuous beam below a loadbearing wall.
- A raft footing is a slab covering the building footprint.
- A pad concentrates the design at a single point, sized by the engineer to the load and to soil bearing capacity.
Common defects on pad footings:
- Pad cast on disturbed fill rather than natural ground: bearing capacity overstated.
- Pad not deep enough below the frost line or seasonal moisture zone (relevant in cool inland sites).
- Reinforcement omitted under the misapprehension that small pads do not need it.
- Post fixing detail (e.g. galvanised post anchor) not cast into the pad at the right elevation.
Also known as: spread footing (loose); column footing; isolated footing.
Category: Structure.
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Last updated: 2026-05-15. Verified: 2026-05-15. Quarterly review for currency.