Poured concrete steps
Concrete steps at a front door, patio or garden slope are a common do-it-yourself project. They are heavier than they look: a short flight with a landing can take more than a cubic yard of concrete. Estimating the volume first tells you whether to mix bags yourself or order a truck.
How the volume is calculated
For solid steps poured on the ground, each step is a block from the ground up to its tread. The first step is one riser high, the second two risers high, and so on. With n steps of rise R, run (tread depth) T and width W:
Steps volume = W × T × R × n(n + 1) ÷ 2
A landing at the top, of depth L, sits one riser above the last step:
Landing volume = W × L × (n + 1) × R
Add 5 to 10% for waste, uneven ground and spillage.
Example
Three steps plus a landing, 48 inches wide, with 7-inch risers, 11-inch treads and a 36-inch-deep landing:
- Steps: 48 × 11 × 7 × 6 = 22,176 in³
- Landing: 48 × 36 × 4 × 7 = 48,384 in³
- Total: 70,560 in³ = 40.8 ft³ = 1.51 yd³
- With 10% waste: 1.66 yd³, about 75 bags of 80 lb premix
At that size, a ready-mix truck or a short-load delivery is usually easier than mixing 75 bags by hand.
Building code limits
The International Residential Code, used by most US states, sets these limits for stairs:
| Item | Limit |
|---|---|
| Riser height | 7¾ in maximum |
| Tread depth | 10 in minimum |
| Variation between risers | ⅜ in maximum |
| Handrail | Required for 4 or more risers |
Outdoor steps are more comfortable with risers of 6 to 7 inches and treads of 12 inches or more, and treads should slope about ¼ inch per foot so water drains.
Building tips
- Base: remove topsoil and compact 4 to 6 inches of gravel. In cold climates, steps attached to the house may need footings below the frost line.
- Reinforcement: #3 or #4 rebar or wire mesh reduces cracking; dowel the steps into the existing foundation when allowed.
- Fill: for large stairs, rubble or compacted gravel inside the forms can reduce concrete, as long as it stays well below the finished surface.
- Finish: use a broom finish for grip, round the nosing edges and keep the concrete moist for at least a week while it cures.