Question 1

How do I calculate concrete for a slab?

Accepted Answer

Multiply length × width × thickness (all in feet). Divide by 27 for cubic yards. For a 10x10 slab at 4 inches: 10×10×0.333÷27 = 1.23 cubic yards.

Question 2

How many bags of concrete for a 10x10 slab?

Accepted Answer

A 10x10 slab at 4 inches thick needs 1.23 cubic yards = 33.3 cubic feet. That's 74 bags of 60lb or 56 bags of 80lb concrete (add 10% waste).

Question 3

How thick should a patio slab be?

Accepted Answer

A standard residential patio should be 4 inches thick for most applications. High-traffic areas or driveways should be 5-6 inches.

Question 4

Do I need rebar in a concrete slab?

Accepted Answer

For patios, wire mesh (6x6-W1.4xW1.4) is sufficient. For driveways or areas with vehicles, use #4 rebar at 18-inch centers.

Question 5

How many bags of concrete per square foot at 4 inches?

Accepted Answer

At 4 inches thick, you need about 0.0617 cubic feet per square foot. That's one 80lb bag (0.60 cu ft) per 9.7 square feet, or roughly 1 bag per 10 sq ft.

Question 6

What is the PSI I need for a residential slab?

Accepted Answer

Most residential slabs call for 3000-4000 PSI concrete. Use 4000 PSI for driveways and areas exposed to freeze-thaw cycles.

Question 7

How long does concrete take to cure?

Accepted Answer

Concrete achieves about 70% of its design strength in 7 days and full strength at 28 days. Keep it moist for the first week.

Question 8

Can I pour a slab in cold weather?

Accepted Answer

Concrete should not be poured when temperatures are below 40°F. Use hot water mixing and insulated blankets if pouring in near-freezing conditions.

Application	Min Thickness	Recommended	PSI
Sidewalk / Walkway	3"	4"	3000
Backyard Patio	3.5"	4"	3000–4000
Residential Driveway	4"	5"	4000
Garage Floor	4"	5–6"	4000
Heavy Equipment Pad	6"	8"	5000

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