Pouring a concrete slab involves eight steps: mark and excavate, build forms, add compacted gravel base, place reinforcement, mix and pour concrete, screed level, finish the surface, and cure for 28 days. For a 10×10 ft patio with bagged concrete, budget a full day with two people.
Materials List (10×10 ft Slab, 4-inch Thick)
| Item | Quantity | Notes |
|---|---|---|
| 80-lb concrete bags (Quikrete) | 62 bags | 33.3 cu ft + 10% waste |
| Crushed stone (#57) | ~0.7 yd³ | 4-inch base layer |
| 2×4 lumber | ~40 linear ft | Form boards |
| Stakes | 16–20 | 2-ft wood or metal stakes |
| Wire mesh (6×6-W1.4) | 2 sheets | 5×10 ft each; overlapped at seams |
| Mesh chairs | 12–16 | Supports mesh at mid-depth |
| Screed board | 1 | 2×4, 12 ft long |
| Release oil or plastic | 1 can/roll | For form boards |
Use the concrete calculator to adjust quantities for your exact slab dimensions.
Step 1: Mark the Area and Check for Utilities
Call 811 at least three business days before any digging. Once utilities are marked, stake out your slab perimeter with string lines. Check for square by measuring both diagonals — they must be equal. Verify that the grade slopes away from any structures at 1–2% (1/4 inch per foot minimum) so water drains off the finished slab.
Step 2: Excavate
Dig out the marked area to a depth of 7–8 inches below finish grade: 4 inches for the gravel base + 4 inches for the concrete slab. Remove all organic material (roots, sod, debris). Compact the native soil with a plate compactor ($80–$120/day rental) or heavy hand tamper.
Step 3: Build Forms
Stake 2×4 boards along the perimeter. The top of the forms sets the finish elevation of the slab, so level them carefully. Use a 4-foot level on the form tops; adjust stakes until level is achieved, or set the desired slope for drainage. Coat the inner face of the forms with vegetable oil or form release spray so they strip cleanly after the pour.
Step 4: Add the Gravel Base
Spread 4 inches of compacted crushed stone (#57 or crusher run) inside the forms. Compact in 2-inch lifts with a plate compactor. Check that the gravel surface is 4 inches below the top of the forms. Add more material in any low spots and re-compact.
Step 5: Place Reinforcement
For a patio, lay 6×6-W1.4/W1.4 wire mesh sheets inside the forms, overlapping seams by 6 inches. Place mesh chairs every 4 feet to hold the mesh at mid-slab depth (about 2 inches from the bottom). For a driveway or garage floor, use #3 rebar at 18-inch centers instead. See rebar-vs-wire-mesh for guidance on which to use.
Critical: Mesh left on the ground gets pushed down during the pour, where it contributes almost nothing. Chairs must keep it at mid-depth.
Step 6: Mix and Pour
With bagged concrete: Mix to the consistency of oatmeal — no puddles on top, workable without cracking. Use a rented drum mixer (about $50/day) for large quantities; a 5-gallon bucket and drill works for amounts under 10 bags. Pour from the farthest corner of the forms outward, filling in a grid pattern. Work concrete into corners with a shovel.
With ready-mix: Have all hands on deck when the truck arrives. Direct the chute to fill the farthest corners first, then work toward the truck. Move quickly — you have 60–90 minutes before the concrete stiffens.
Water ratio: Follow the bag instructions. Adding extra water makes the concrete easier to pour but significantly reduces its strength. Each extra inch of slump from excess water reduces compressive strength by approximately 250 psi, per the Portland Cement Association.
Step 7: Screed and Float
Draw a 2×4 screed board across the tops of the forms in a sawing motion, removing high spots and filling low spots. Work in 2–3 passes until the surface is level with the forms.
After screeding, run a bull float or darby over the surface to embed aggregate, flatten trowel marks, and bring cream (water and cement paste) to the top. Work in long, overlapping strokes. Do not overwork — excessive floating weakens the surface layer.
Wait for bleed water (the sheen on the surface) to evaporate before finishing. This takes 30–90 minutes depending on temperature and humidity. Starting to finish before the bleed water evaporates is one of the most common mistakes and weakens the surface significantly.
Step 8: Finish the Surface
Once the bleed water is gone and the concrete can support a trowel without sinking more than 1/8 inch, finish with:
- Broom finish — drag a broom across the still-pliable surface for traction. Standard for exterior slabs.
- Steel trowel finish — creates a smooth, hard surface. Used for interior floors.
Use an edging tool along the perimeter where the slab meets the forms to create a rounded edge. Cut control joints (grooves) every 8–10 feet or at a maximum spacing equal to the slab thickness in inches squared (4-inch slab = joints every 16 ft maximum per ACI 302). Control joints give the concrete a place to crack in a straight, predictable line rather than randomly.
Curing: Do Not Skip This
Immediately after finishing, apply a curing compound spray or cover the slab with wet burlap and plastic sheeting. Keep it moist for 7 days. Do not walk on the slab for 24–48 hours; no vehicle traffic for 7 days. Full strength in 28 days. For the full cure timeline, see concrete-cure-time.
Common Mistakes to Avoid
Adding too much water. When the mix is stiff, it is tempting to add water. Resist. Use a drill-powered mixer longer, or accept a stiffer pour.
Starting to finish too early. If you trowel before the bleed water evaporates, you trap water in the surface layer. The resulting surface is weak and will dust and peel over time.
No control joints. Without joints, concrete cracks where it wants to. Joints do not prevent cracking — they control where cracks occur, keeping them invisible inside the groove.
Forms pulled too early. At 24 hours, concrete is walkable but the edges and corners can still be chipped by form removal. Pull forms slowly and support the slab edge with a hand as you strip.
Skipping the gravel base. A 4-inch compacted gravel base costs $50–$100 in materials for a 10×10 slab. Skipping it to save time risks the entire pour if the native soil settles or frost heaves.
Safety
- Wet concrete is alkaline (pH 12–13). Wear nitrile gloves, long sleeves, and safety glasses throughout the pour and finishing.
- Do not rest your knees on fresh concrete when finishing — concrete knee burns are a common and serious injury.
- In hot weather, pour early in the morning and keep the surface shaded and moist.
- In cold weather (below 40°F), do not pour. Concrete that freezes before setting is permanently damaged.