Concrete Mixing & Pouring

Concrete is cheap to buy and expensive to redo. The two things that decide whether a pour lasts decades or cracks in a season are the water content and the cure — get those right and the rest is straightforward. This guide covers mixing and pouring for slabs, footings, and post holes.

What you'll need

First, figure out how much concrete the job takes with the Concrete Calculator(it gives bags or cubic yards), and the base gravel with the Gravel Calculator. You'll also want:

• Concrete — bagged pre-mix for small jobs, or ready-mix delivery for large pours.
• Gravel for the base, plus form boards and stakes to shape the pour.
• Reinforcement — welded wire mesh or rebar, with chairs to hold it mid-slab.
• A mixing tub or wheelbarrow (or a mixer), a screed board, a float, an edger, and a trowel.
• Gloves and eye protection — wet concrete is caustic.

Step by step

1. Calculate the volume. Work out cubic feet/yards (or bags) so you can place the whole pour in one continuous go — cold joints between batches are weak points.
2. Prep the base. Excavate, add and compact a gravel base for drainage and support, then build and level your forms.
3. Add reinforcement. Lay wire mesh or rebar and raise it on chairs so it ends up in the middle of the slab, not on the dirt.
4. Mix the concrete. Add most of the water, mix to a workable consistency that holds its shape, then add the rest sparingly. Resist the urge to make it soupy.
5. Pour and spread. Place concrete evenly across the forms, working it into corners and edges and removing air pockets.
6. Screed level. Drag a straight board across the top of the forms in a sawing motion to strike off the excess and level the surface.
7. Float and finish. Float to bring up a smooth surface, run an edger along the forms, cut control joints, and add a broom finish for slip resistance if desired.
8. Cure it slowly. Keep the surface damp (mist it or cover it) for several days. Slow, moist curing is what builds strength.

Curing & strength timeline

• ~24–48 hours: firm enough to walk on.
• ~7 days: roughly 70% strength; light traffic is generally OK.
• ~28 days: full design strength; heavy loads.
• Keep it moist during the first several days — don't let it dry out fast.

Common mistakes to avoid

• Too much water — the single most common cause of weak, dusty, cracking concrete.
• Skipping the gravel base or pouring on uncompacted ground.
• Letting concrete dry instead of curing it moist.
• Pouring in freezing or scorching conditions without precautions.
• Leaving out control joints, so the slab cracks where it wants to instead of where you planned.