How to Pour a Concrete Slab

Patio furniture on a concrete slab

People pour concrete slabs for all kinds of reasons. Home foundations, patios and sidewalks are some common ones. The purposes vary, but the directions pretty much stay the same. Here’s how to pour a concrete slab, along with some tips to make the job successful. 

Note: When working with cement-based products, always wear eye protection and waterproof gloves.

Construct wood form for concrete slab

Step 1: Prepare the Site and Construct the Form

Every strong concrete slab starts with a well-built form. 

First, excavate the slab area to a depth of about 7 inches, allowing 3 inches for a gravel base and 4 inches for concrete.

Then construct the form with 2-by-4 or 2-by-6 lumber, and secure it in place with wood stakes and deck screws.

Leveling wood form

Step 2: Level the Form

Make sure the form is level, allowing ¼ inch slope for every 12 feet of the slab. This allows for rain run-off to protect the concrete.

Keep in mind that patio and sidewalk forms should slope evenly away from structures. It’s important to direct rainwater away from the home’s foundation to prevent soil erosion.

Add gravel base to form

Step 3: Add the Gravel Base

A solid sub-base will help prevent erosion and slab settling.

Pour 3 to 4 inches of QUIKRETE All-Purpose Gravel in the form, and even it out.

Using a tamp to compact gravel base

Step 4: Compact Gravel Base

Compact the gravel base in the form using a tamp. A solid sub-base will help prevent erosion and slab settling.

Dampening gravel base with hose

Step 5: Dampen the Gravel

Dampen the gravel base using a garden hose. This will help prevent shrinkage and cracking, especially in hot temperatures.

Pouring concrete in form

Step 6: Pour the Concrete

Determine how much concrete you’ll need with Quikrete’s easy-to-use Concrete Calculator. Just enter the square feet of your project, and Quikrete will eliminate any guesswork.

Mix up Quikrete Concrete Mix, as directed on the package, and evenly pour it into the form.

Tip: The tops of the concrete mounds should be about 2 to 3 inches above the form before leveling.

Spreading concrete out in form with a hoe.

Step 7: Spread the Concrete

Use a hoe to consolidate and distribute the concrete evenly in the form. The concrete’s surface should be relatively flat and slightly above the form.

Using a board to screed the concrete level with the form.

Step 8: Screed Concrete

Use a straight 2-by-4 as a screed to level the concrete to the form. Move the board back and forth across the surface of the concrete in a sawing motion. 

Then, use the top of the form as a guide to remove excess concrete and smooth the surface.

Add concrete and screed level

Step 9: Fill in the Low Areas

Despite screeding the concrete, you’re bound to still have some areas that need a bit more concrete. 

Add concrete wherever it’s needed and, once again, screed the concrete so it is level with the form. You may have to do this a few times to get it just right.

Using a wood float to smooth surface of concrete slab

Step 10: Run a Float Over the Concrete

Once the concrete has lost its sheen, smooth its surface using a wood float in an arcing motion.

After that, drag a stiff-bristle broom over the concrete to create a non-slip finish. Make all the broom strokes in the same direction.

Cut control joints

Step 11: Cut Control Joints

All building materials expand and contract with extreme thermal changes. Cutting control joints in the concrete slab helps to reduce the impact — and potential cracks that could form — as seasons change. 

Cut control joints a minimum of 1/4 the slab’s depth using a groover and a straight edge. A 4-inch-thick slab requires control joints every 10 feet, at minimum, in each direction.

Using edging tool to round edges of concrete slab

Step 12: Edge the Concrete

Use an edging tool to consolidate and shape the slab’s edges. Make several passes in each direction for a smooth finish.

Misting concrete slab with hose while curing

Step 13: Allow the Concrete to Cure

Water-cure freshly placed concrete for a minimum of 3 to 5 days with a fine water mist.

TIP: Instead of water-curing, you can apply QUIKRETE Acrylic Concrete Cure & Seal immediately after finishing the concrete. Acrylic Cure & Seal can be applied with a roller, garden sprayer or a brush.

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