How to Pour a Concrete Slab
The Six Steps, with Honest Time Estimates
| Step | Time (10×10 slab) | What happens |
|---|---|---|
| 1. Site prep & layout | ½ day | Stake and string the outline, square it (3-4-5), strip sod, dig to depth |
| 2. Build the forms | ½–1 day | 2× lumber on edge, stakes every 2–3 ft, screed height = slab thickness |
| 3. Base & reinforcement | ½ day | 4 in. compacted gravel, mesh or rebar on chairs, not on the dirt |
| 4. Pour & screed | 2–4 hours | Fill to the form tops, screed rail working side to side |
| 5. Float & edge | 1–2 hours | Bull float as bleed water sheen fades; edge and joint the perimeter |
| 6. Finish & cure | 30 min + a week | Broom or trowel, then cure — wet, covered or compound — for 7 days |
How to Build Concrete Forms That Hold
Forms are just 2× lumber set on edge at the slab's finished height — but three details separate flat slabs from failed ones. Square it with the 3-4-5 rule (or measure both diagonals) before a single stake goes in. Stake tight — a stake every 2–3 feet, because wet concrete pushes outward with real force and a bowed form is permanent. Set the grade — the form top is the finished floor, so level or slope it ⅛–¼ inch per foot away from the house for drainage. Oil or wet the inner face so the lumber releases.
The Pour, Finishing and Curing
- Order 10% extra and have every tool on site before the truck arrives — concrete waits for no one.
- Screed with a straight rail riding the form tops, sawing side to side as you pull.
- Wait for the sheen before bull-floating; troweling bleed water back in weakens the surface.
- Cut control joints to a quarter of the slab depth, spaced 8–12 ft apart, within 24 hours — or tool them in while finishing.
- Cure for 7 days — compound, plastic or damp burlap — before any real load. Skip it and the surface dusts and cracks regardless of how well the pour went.
Small pours mix from bags; anywhere near a yard, book the truck — the mixing walkthrough covers the bag route end to end.
When to Call a Pro Instead
Slabs over a few yards, anything structural, driveways (thickened edges and vehicle loads), and pours that must match an existing finish are all faster and often cheaper done by a crew — quote against the installed per-square-foot rates before committing a weekend.
Frequently Asked Questions
How thick should a poured slab be?
Four inches for patios, walkways and shed bases; five to six for driveways or anything with vehicles. Whatever you choose goes into the math first — thickness is the single biggest driver of the order size.
Do I need rebar or is mesh enough?
For a 4-inch patio or walkway, 6×6 wire mesh or fiber-mixed concrete is standard. Driveways, shed-bearing pads and anything loaded benefit from #4 rebar on 18–24 inch centers, chaired mid-slab — not laid on the dirt.
Can I pour a slab directly on dirt?
Never on bare soil — it drinks water out of the mix unevenly and heaves with frost. Four inches of compacted gravel over landscape fabric is the minimum base; it levels support and keeps the cure even.
What if it rains right after I pour?
Rain inside the first 4–8 hours pits and weakens the surface; keep plastic sheeting on site and cover at the first drops. Once the slab has set hard — typically the next morning — rain is harmless.