Footings transfer the load of a structure into the ground. Whether you're building a house, an addition, a deck, a retaining wall, or a fence, the footing is what keeps everything from settling, shifting, or sinking. Getting the concrete right — the right mix, the right volume, and the right amount of overage — is critical.

What PSI Do Footings Need?

Most residential footings are poured at 3,000 PSI. For heavier loads — multi-story structures, commercial buildings, or areas with poor soil bearing capacity — 3,500 to 4,000 PSI is appropriate. Always check your local building code and any engineered drawings before ordering.

• 3,000 PSI — standard residential footings, decks, additions
• 3,500 PSI — heavier residential loads, two-story additions
• 4,000 PSI — commercial footings, engineered structures

Calculating Cubic Yards for Footings

Footings are typically rectangular in cross-section. To calculate volume: multiply the length (ft) × width (ft) × depth (ft), then divide by 27.

For spread footings (individual column pads), calculate each pad separately and add them together. Don't forget to include any grade beams or thickened edges.

Why You Always Need Extra

Footing trenches are dug by machine or hand — they're never perfectly uniform. The bottom may be uneven, the walls may slough in, and the actual dimensions often vary from the plan. A trench that's supposed to be 16 inches wide may be 18 inches in places. These variations add up fast.

Always add a minimum of 10% overage to your footing calculation. On longer runs or in areas with loose or rocky soil, 15% is safer. Running out of concrete mid-footing is a serious problem — you'll have a cold joint at the stopping point, which is a structural weakness and a potential code violation.

Footing Depth and Frost Line

In the Charlotte, NC area, the frost depth is relatively shallow (typically 6–12 inches), but footings for permanent structures still need to be below the frost line and into undisturbed soil. Check with your local building department for the required depth — it varies by structure type and jurisdiction.

Rebar in Footings

Most structural footings require rebar. Typical residential continuous footings use two runs of #4 rebar placed horizontally, 3 inches from the bottom of the form. Spread footings may require a rebar mat. Your engineer's drawings or local code will specify the requirements — don't skip the steel.

Placement Tips

• Wet the trench before pouring in hot weather to prevent rapid moisture loss
• Use a vibrator to consolidate the concrete around rebar and eliminate voids
• Strike off the top of the footing level — it's the reference plane for everything above
• Protect from rain for the first 24 hours; cover with plastic if needed

UNO Concrete delivers footing mixes to job sites across the Charlotte metro. Give us your footing dimensions, rebar layout, and pour date — we'll calculate the right volume, recommend the right mix, and get it there on time.