Make It Smooth: How to Pour a Concrete Slab

Thinking about pouring a concrete slab? It can be an easy way to give your outdoor entertainment space a facelift. Plus, you can knock out a small slab as a weekend DIY project and be back to grilling on solid ground, er, concrete patio in no time! Good preparation and planning are key when working with concrete. Follow our guide to learn how to get this project done right.

Concrete might seem harmless, but it can cause serious damage to exposed skin.

• Wear sturdy boots (rubber is best).
• Cover your skin with long pants and a shirt.
• Protect your face and eyes with safety goggles.
• Protect your airway with a respirator or dust mask.
• Treatment: If you get wet concrete on your skin or clothes, immediately wash thoroughly. Severe or widespread cement burns can require emergency medical treatment.

1. Permits: Permitting will vary depending on the size of your project, the grade (slope) of it, and your local building codes. Take a look at our guide to answer some preliminary questions. Do you need a permit?
2. Calculations: Start your project planning by calculating how much concrete you need to complete your new patio, walkway, or even small shed slab. A few simple measurements of the work area are all you need to get going.
3. Vocabulary: Get familiar with the ingredients for your project, with a quick refresher on the difference between concrete and cement, and other key terms for working with this building material.

The best type of weather to pour a concrete slab in is around 70 degrees F during and for at least five days after pouring. You should also make sure the evening lows are above 40 degrees F (any lower can cause the concrete to crack). Warm temps are better than cooler ones, but you can pour it in conditions as low as 50 degrees. Pouring before 10am on hot days is best. It’s also best to not pour in rainy conditions, but it’s not a deal breaker.

For a project like a patio, you’ll need at least a wheelbarrow to mix in. Larger projects can also be mixed in a portable cement mixer, which can be rented. You will use a wheelbarrow in this case to transport the mixture to the slab location.

Start your mixing by adding all of the dry concrete mix, and about³/₄ of the recommended amount of water to the wheelbarrow. Then use a garden hoe or shovel to mix the water and concrete. Add remaining water slowly (about 2 oz. at a time) and don’t add too much! Your concrete will be stronger the less water it has in it. You should aim for a uniform consistency like peanut butter.

What Tools and Materials Are Needed

Tools:

• Hammer
• Level
• Electric miter saw or circular saw
• Concrete hand/bull float
• Mixing hoe
• Hose and water supply
• Wheelbarrow
• Measuring tape
• Speed square or carpenter's square
• Twine/mason's line
• Shovel
• Tamper

Materials:

Note: The exact amount of concrete and gravel you’ll need will depend on the size of the slab you’re pouring.

• Bags of ready-mix concrete
• Bags of all-purpose gravel
• Rebar or reinforcement mesh and rebar ties (if needed, it may not be if you use “crack-resistant ready-mix concrete”)
• 2 x 4s, 8-ft each
• Wood stakes
• Deck screws
• 16d galvanized nails, 3 1/2 inch
• Vegetable oil or concrete release agent
• 6-mil plastic sheeting (enough to cover slab)

1. Lay out the area of the slab. When you are working on an existing lawn or natural area, remove the sod around the perimeter of your project. Also, remove an additional buffer zone of approximately six inches. This will help ensure a clean and well-defined area for your project. The average depth for a small concrete slab, such as a small patio, is four inches. (Use your level to determine the slope and thickness of your slab, since it should also drain away from structures.)
   Use a tamper to bring the remaining dirt surface to a smooth(ish) surface. Add gravel. While you can pour concrete on level and compacted dirt, it’s best to use even a small, four-inch layer of flattened gravel under your concrete slab. Gravel helps the concrete avoid absorbing and eroding moisture in the soil.
2. Set the four corners of your slab using the hammer and stakes, and tightly wind the twine around each several times to create an outline of the area for your project. Use the 2x4s and cut them to the length needed for your slab space using the saws. Connect the 2x4s with the 16d galvanized nails. Place the form in the area you marked earlier with stakes and twine. Ensure the form is level, but also allows for slightly sloped drainage away from nearby structures.
3. Lay rebar or reinforcement mesh above the gravel. For a four-inch concrete slab, rebar should be laid two inches below the surface. For rebar mesh, lay down panels covering the entire slab area, except for three inches around the outside perimeter. Use rebar ties to connect the mesh panels. If you use rebar, create a grid of rebar stakes every two feet, connecting with rebar ties where the points overlap.
4. Apply vegetable oil or a release agent to the frame. Then lightly wet the frame and gravel with water from the hose.
5. Mix and pour the concrete in the wheelbarrow, following the manufacturer’s instructions, and working quickly (a helper or two can be especially efficient during this stage). You can tip the mixed concrete into the slab area and scrape it into the form using a concrete mixing hoe or shovel.
6. Screed and level. After all the concrete has been added, use a spare 2x4 to “screed” the concrete. This is an initial leveling that may see some excess concrete come out of the sides of the form. Then flatten the surface of the slab using the concrete float. This will push the aggregate down and bring moisture up out of the concrete to create an evenly drying, smooth surface. About 10-20 minutes after floating, use a concrete trowel to do a final smoothing of the surface.
7. Make final touches. Using the hand edger, round the edges, and use the side to add joints along the long side of the slab to act as “contraction” joints. Run a stiff broom along the top of the slab to add texture. Then remove the forms.
8. Cure the concrete. Keep moisture even on the slab by lightly spraying it over a 48-hour period and keeping it covered with plastic sheeting. This will keep the concrete from drying out too fast and cracking. You can walk on the slab after 48 hours but wait seven to ten days to add furniture or other items.

We love the sight of a slab pour because we know that’s just the beginning of something great! Talk to the experts at every McCoy’s to make sure your new walkway or patio project is on the right path from the start. We can make it even easier and deliver all your materials right to your backyard or project site!