How much concrete do I need for a 10×10 patio?
For a 10' × 10' patio at standard 4" thickness: 33.33 cubic feet, or about 1.24 cubic yards. Add 10% waste, you'll need to order 1.5 cu yd (the typical minimum truck order) or roughly 62 bags of 80 lb concrete. Ready-mix is usually more economical at this size — bagged concrete becomes labor-intensive.
How many bags of concrete do I need per cubic yard?
Per cubic yard (27 cubic feet): 45 bags of 80 lb (each yields 0.6 cu ft), 60 bags of 60 lb (each yields 0.45 cu ft), or 90 bags of 40 lb (each yields 0.3 cu ft). 80 lb bags are the most cost-effective and labor-efficient per cubic yard, but 60 lb bags are easier to handle if you're working solo.
Why round up to nearest 0.5 cubic yard?
Ready-mix trucks typically deliver in 0.25 or 0.5 cu yd increments. You can order 1.5, 1.75, 2.0 cu yd — not 1.36 cu yd. Always round UP because running short during a pour creates a "cold joint" that's structurally weaker. Excess concrete can be poured into temporary forms for splash blocks, stepping stones, or just spread thin on disposal area.
How thick should my concrete slab be?
Patios and walkways: 4 inches. Driveways for cars: 4-5 inches. Heavy vehicles or RV parking: 6 inches. Garage floors: 4 inches (5-6" if heavy equipment). Foundation slabs: 4-6 inches per code. Pool decks: 4 inches. Going thinner risks cracking under load; going thicker wastes concrete. Always check local building codes for foundation requirements.
How long until concrete is fully cured?
Initial set: 24-48 hours (light foot traffic only). 50% strength in 7 days. 90% strength in 28 days (the standard "design strength" measurement). Full cure: months. Keep concrete moist during the first 7 days for best curing — drying out too fast weakens it. Avoid vehicle traffic for at least 7 days, ideally 28. Sealing improves long-term durability.
Do I need rebar in concrete?
For most slabs over 4 inches thick, yes. Rebar (typically #4, 1/2" diameter) on 12-18" grid prevents structural cracking. For thinner slabs (sidewalks, patios), wire mesh or fiber-reinforced concrete may suffice. For driveways and foundations, rebar is standard. Foundations, columns, and walls always need rebar — building code typically mandates this.
Why does concrete crack?
Concrete shrinks slightly as it cures (about 1/16" per 10 feet). Without control joints (cut grooves at planned crack locations), random cracks form. Other causes: insufficient curing moisture, expansion/contraction from temperature, settling subbase, overloading. Some cracking is normal and cosmetic. Cut control joints every 8-10 feet, 1/4 the slab thickness deep. Sealing prevents water infiltration of any cracks.
Bagged vs ready-mix: which is cheaper?
Per cubic yard, ready-mix usually wins for 1+ cu yd projects. Example: 1 cu yd of ready-mix = ~$185. Same yard in 80 lb bags = 45 × $7 = $315. Below 0.5 cu yd, bags often win because of short-load fees on ready-mix delivery (typically $50-150 surcharge). The crossover is generally around 1 cu yd, but factor in your labor — mixing bags is exhausting.
What's the difference between concrete and cement?
Concrete is the finished material; cement is one ingredient. Concrete = cement + aggregate (sand and gravel) + water. Cement is the binding agent (typically Portland cement). When people say "cement driveway" they really mean concrete. Pure cement is much weaker and only used for things like grout. Bagged "concrete mix" already contains cement, sand, and gravel — just add water.
Can I pour concrete in cold or hot weather?
Cold (under 40°F): risky without precautions. Concrete must stay above freezing for 24-72 hours after pouring. Use cold-weather mix with calcium chloride accelerator, insulating blankets, and warm water. Hot (above 90°F): concrete dries too fast and weakens. Pour early morning, use cool water, add retarders, mist surface during curing. Spring and fall are ideal pouring conditions.
How heavy is concrete?
Standard concrete weighs about 150 lb per cubic foot (4,050 lb per cubic yard, or about 2,400 kg/m³). So that 1.5 cu yd patio order weighs about 6,000 lb — heavier than most cars. Concrete is heavy because of dense aggregate. Lightweight concrete (with pumice or expanded clay) weighs 90-115 lb/cu ft and is used for upper floors and roof slabs in commercial construction.
Do I need a permit?
Depends on location and project type. Usually required: foundations, structural slabs, retaining walls over 4 feet, work near property lines, new construction. Usually not required: replacing existing slabs of same size, small patios, sidewalk repairs. Always check with your local building department. Skipping required permits can affect insurance claims, future home sales, and result in fines.
