How to Pour a Concrete Slab

Step-by-step

1. 1

   Plan and mark the slab

   Lay out the perimeter with stakes and mason line. Confirm dimensions square by measuring diagonals — they must match within 1/8". Slope 1/4" per foot away from any structure for drainage.

2. 2

   Excavate and compact the base

   Dig 6–8" deep. Add 4" of compactable gravel in 2" lifts, tamping each lift. A firm base is what keeps a slab from cracking; skip this and the concrete will telegraph every soft spot.

3. 3

   Build forms

   Screw 2x4s to stakes every 3–4 feet along the perimeter. Check the top of forms with a level — that's the finish grade of your slab. Coat form faces with form-release oil or old motor oil for clean removal.

4. 4

   Set reinforcement

   Lay 6x6 W1.4 wire mesh or #3 rebar in a 16" grid, elevated on 2" chairs so it sits in the middle of the slab thickness. Reinforcement in the bottom does nothing.

5. 5

   Pour and screed

   Start pouring at the far corner. Rake concrete into place slightly proud of the forms, then screed with a 2x4 in a sawing motion across the forms. Work in 8–10 ft sections.

6. 6

   Bull float, edge, and groove

   Once bleed water disappears, bull float to close the surface. Run an edger along the perimeter and cut control joints every 8–10 feet with a groover to control cracking.

7. 7

   Final finish and cure

   For a broom finish, drag a soft broom across after the surface firms up. Cover with plastic sheeting and keep damp for 5–7 days. Do not walk on the slab for 24 hours; do not park on it for 7 days.

Safety note: this guide is educational. Always follow local building codes, pull required permits, and hire a licensed pro for structural, electrical, gas or plumbing work when in doubt.