Footings sit in damp soil for the life of the building, out of sight. The cement for them should be chosen for that life, not for how fast it sets.
Cement Types for Foundations
| Type | Strengths below ground | When to choose |
|---|---|---|
| PPC | Dense, low permeability, good sulphate resistance, lower heat | Ordinary soils — the common choice |
| PSC | Very good sulphate and chloride resistance | Aggressive or saline soils, near drains |
| OPC 43/53 | High early strength | Where specified, or a tight schedule |
The Grade and Detailing
| Item | Typical requirement |
|---|---|
| Concrete grade | At least M25 (moderate exposure) |
| Water-cement ratio | Not more than 0.50 |
| Cover | 50 mm |
| PCC bed | M10–M15 under the footing |
Curing Below Ground
Footings are often backfilled within days, before they have cured. Keep them wet — covered with wet hessian, or flooded where the pit allows — for at least 7 days with OPC and 10 with PPC before backfilling.
How Much Cement?
The foundation and plinth stage typically uses about a fifth to a quarter of a house's cement — around 80–100 bags for a 1,000 sq ft house. Buy it as one fresh lot.
The Short Version
PPC for most foundations, PSC for aggressive soils, OPC where specified — in M25, with 50 mm cover, cured properly before the soil goes back.
