Concrete Slab Instructions

Concrete is among the most durable of building materials.

Pouring a concrete slab is not a project for beginning do-it-yourselfers, but can be a big money-saver for more experienced homeowners. There's a lot of room for error, but if you're attentive to detail, you'll get a finished concrete slab that will last for years. Contact your local building department to inquire about your local building codes and any needed permits. Don't try to pour concrete when it's hot, windy or rainy, or you might not end up with a smooth surface.

Things You'll Need

• Builder's level
• Garden spade
• Measuring tape
• Lumber
• Saw
• Hammer
• String
• Gravel
• Plate compactor
• 10/10 reinforcing wire
• 2-inch dobies
• Tie wires
• Tie-wire twisting tool
• Concrete mix
• Power mixer
• Portland cement
• Sand
• Water
• Wheelbarrow
• Shovel
• Garden rake
• Bull float
• Edging tool
• Groover
• Metal float
• Garage broom
• Curing compound
• Garden sprayer

Instructions

Prepare the Site

1. See if the ground slopes where you will pour your concrete slab using a builder's level. If it slopes, you will build up the low side later.

2. Remove the sod from the area with a garden spade. Roll the sod up if you want to re-use it. Remove the topsoil.

3. Cut two 2-by-12-inch pieces of lumber to be 3 inches longer than the length of the concrete slab. Cut two 2-by-12-inch pieces of lumber to the exact width of the slab.

4. Nail the pieces of lumber together to form a frame for the concrete slab. Place the width boards inside the length boards to ensure the frame is the correct size. Use a builder's level to ensure that your frame is level on the ground. Prop up one side of the frame if you are going to fill in a low end. The top of the frame will be the top of the concrete slab.

5. Cut 2-by-4-inch lumber into pieces 20 inches long. Drive one of these pieces into the ground every 2 feet along the outside of the wooden frame. Support these braces with more pieces of 2-by-4-inch lumber placed diagonally against the outside of the braces. This supports the frame against the weight of the fresh concrete.

6. Hold a string across the top of the wooden form in several places and measure the distance to the ground. Average the numbers and subtract the thickness of your concrete slab. Use this number to calculate how much gravel you will need to order.

7. Spread gravel inside your wooden form, leaving a 12-by-12-inch trench around the perimeter so that the edges of your concrete slab will be thicker than the rest of it. Place more gravel on the low spots, if you found any in Step 1. Tamp down the gravel with a plate compactor after adding each 3 inches of gravel.

8. Cover the gravel with 10/10 reinforcing wire laid on top of 2-inch dobies, which are supports for reinforcing wire. Attach every fourth intersection of the mesh to a dobie with a tie wire twisted with w tie-wire twisting tool.

Pour the Concrete

1. Mix your concrete in a power mixer. Combine 1 part portland cement, 2 parts sand and 3 parts gravel in the power mixer. Add 1/4-part water slowly. A sales associate at your local home-improvement center can help you determine the amount of materials you need to mix for your concrete slab, depending on its finished dimensions.

2. Transfer the first batch of mixed concrete to a wheelbarrow and transport it to the corner of the wood frame farthest from the power mixer. Pour the concrete into the form and spread it with a shovel or garden rake. Continue until the concrete reaches the top of the wood frame, then add the concrete in different spots until the entire frame is filled.

3. When the concrete reaches the top of the frame in one section, drag a 2-by-4-inch piece of wood over the surface of the concrete, smoothing it and pushing excess concrete to less-filled areas of the frame. This is called screeding.

4. Smooth the surface of the concrete with a bull float, tilting it so that the leading edge of the bull float is above the concrete surface. Run the bull float over the concrete three or four times.

5. Allow the water on top of the concrete to dry, and let the concrete begin to harden. Press a finger into the concrete to test for hardness. If your finger doesn't leave a mark in the concrete, it is hard enough to continue.

6. Create a rounded edge on your concrete slab by pressing an edging tool around the perimeter of the slab, just inside the wood frame.

7. Create grooves in your concrete slab to prevent cracking. Press a grooving tool into the concrete, using a 2-by-4-inch piece of lumber as a straight edge. Make a groove every 10 feet. If your concrete slab is less than 10 feet in either direction, skip this step.

8. Smooth the surface with a metal float. Wet the bristles of a garage broom and draw it over the surface of the concrete slab, creating a texture that is non-slip.

9. Spray curing compound on the concrete with a garden sprayer, following the manufacturer's instructions. Let the concrete cure overnight. Remove the wood frame.

Tips & Warnings

• If your concrete slab is more than 100 square feet, hire a concrete truck to mix the concrete for you.

References

• The Family Handyman: Form and Pour a Concrete Slab
• "Tiling"; Better Homes and Gardens; 2005