Question 1

How much money can I save by pouring my own concrete slab?

Accepted Answer

DIY concrete saves you the labour portion of the cost — typically 40–50% of total installed price, or $2–$5/sqft. For a 10×12 shed pad (120 sq ft), DIY total cost is $400–$600 (materials + rental) vs $600–$1,200 contractor installed — savings of $200–$600. For a 20×20 patio, DIY total might be $1,000–$1,600 vs a contractor price of $2,000–$4,000 — savings of $1,000–$2,500. The catch: quality is highly dependent on your finishing skill and the timing of the pour.

Question 2

How many bags of concrete do I need for a 10×10 slab?

Accepted Answer

A 10×10 ft slab at 4-inch thickness requires 1.23 cubic yards of concrete. At 0.6 cubic feet per 80 lb bag (and 27 cubic feet per cubic yard), that's 1.23 × 27 / 0.6 = 55.4, so approximately 56 bags of 80 lb concrete mix. Add 10% waste = 62 bags. At roughly $7.00 per bag at Home Depot, materials cost approximately $435. Plus gravel base, form lumber, and tool rental, total DIY project cost is $600–$900.

Question 3

Can a beginner pour their own concrete slab?

Accepted Answer

Yes — for small pours (under 100 sq ft, like a shed pad or AC unit base). The keys to DIY success: (1) Proper gravel base (4-inch compacted) — don't skip this; (2) Correct water-to-mix ratio — too much water weakens the concrete; (3) Screed while concrete is wet, float before it stiffens, edge before it sets; (4) Have everything set up before opening the first bag — concrete waits for nobody; (5) Have 1–2 helpers for anything over 50 sq ft.

Question 4

What are the most common DIY concrete mistakes?

Accepted Answer

The seven most common DIY concrete mistakes: (1) Skipping the gravel base (causes settling and cracking); (2) Adding too much water (weakens concrete by 30%+ per extra quart/bag); (3) No expansion joints (causes random cracking instead of controlled cracking); (4) Finishing too early while bleed water is still on the surface (weakens the top layer); (5) Not curing properly (cover with plastic or wet burlap for 7 days); (6) Under-reinforcing (no mesh or rebar when mesh is appropriate); (7) Pouring in extreme heat without retarder or in extreme cold without accelerator.

Question 5

When should I always hire a contractor?

Accepted Answer

Always hire for: (1) Any foundation work — structural consequences, code-required inspections, engineering required; (2) Any slab over 300 sq ft — timing and finishing a large pour before it stiffens requires an experienced crew; (3) Driveways and garage floors — vehicle loads require proper reinforcement that's difficult to DIY correctly; (4) Cold-weather pours below 40°F — temperature management requires experience; (5) Sloped sites requiring retaining forms; (6) Any pour requiring a building permit inspection before pouring — you need a licensed contractor's name on the permit in most jurisdictions.

Project	Skill Level	DIY Verdict	Est. Savings	Notes
AC unit / generator pad (9–25 sqft)	Beginner	DIY	$150–$300	Ideal first concrete project. Bagged mix, minimal forming.
Small shed pad (80–120 sqft)	Beginner	DIY	$200–$500	Most common DIY pour. Rent a mixer. Need 1 helper.
Medium shed pad / small patio (150–200 sqft)	Intermediate	DIY with prep	$400–$800	Order ready-mix. Timing pressure. Need 2–3 helpers.
Concrete patio (200–400 sqft)	Intermediate	Assisted DIY	$600–$1,500	Do the forming yourself; hire a finisher for the pour and finish.
Driveway (400–800 sqft)	Expert	Hire out	Risk of failure > savings	Expansion joints, timing, vehicle loads. Not recommended DIY.
Garage floor (400–900 sqft)	Expert	Hire out	Risk of failure > savings	6-inch, rebar, large volume, timing critical.
Foundation slab	Professional only	Always hire	Never DIY	Structural, code, inspections. Failure consequences severe.

Tool	Cost	Notes
Concrete mixer rental (3.5 cu ft)	$75–$150/day	For pours up to ~0.5 cu yd / day
Plate compactor rental	$80–$120/day	For gravel base compaction — essential
Bull float (48-inch)	$25–$50 (buy)	For smoothing large slab surfaces
Magnesium hand float	$15–$30 (buy)	Final surface finishing
Concrete edger	$10–$20 (buy)	Rounds the slab edges
Jointing tool (groover)	$15–$30 (buy)	Cuts control joints into fresh concrete
Screed board (2×4, cut to width)	Free	Level the surface — use existing lumber
Safety: gloves, knee pads, eye protection, respirator	$40–$80	Concrete is caustic — skin protection essential
Wheelbarrow	$60–$100 (buy) or borrow	For moving bagged mix and concrete
Curing blankets (rental)	$15–$30/day	Required for cold-weather or hot-weather pours

Factor	Bagged Concrete	Ready-Mix
Best for	Pours under 1 cubic yard	Pours over 1 cubic yard
Cost (concrete only)	$7/bag × bags needed	$120–$200/cu yd + delivery + short-load fee
Timing flexibility	Mix batch by batch at your pace	3–5 hours to place entire delivery
Quality control	Manual mixing; easy to over-water	Consistent factory mix
Equipment needed	Mixer rental ($75–$150/day)	Wheelbarrow + chute access
Typical 10×10 slab (4-inch)	56 bags ≈ $395 materials	1.23 cu yd ≈ $250–$400 + delivery fee

Project	Forming	Pour & Finish	Total (2 people)
AC unit pad (3×3, bagged)	30 min	1 hour	1.5 hours
Shed pad (8×10, bagged)	1–2 hours	2 hours	3–4 hours
Small patio (12×12)	2–3 hours	2–3 hours	5–7 hours
Medium patio (16×20, ready-mix)	3–4 hours	3–4 hours	7–9 hours
Large patio (20×30, ready-mix)	4–6 hours	4–5 hours	9–12 hours + crew of 3

Project	Full DIY	Assisted DIY*	Full Contractor	DIY Savings
Shed pad 10×12	$380–$550	N/A	$700–$1,200	$300–$700
Small patio 12×16	$550–$800	$900–$1,200	$1,200–$2,300	$400–$1,500
Patio 20×20	$900–$1,400	$1,400–$1,900	$2,500–$5,000	$1,100–$3,600

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Labour Time Estimates

DIY vs Contractor Cost Comparison

DIY Concrete FAQ