Pouring A Concrete Patio: Steps And Guide

Pouring a concrete patio is a challenging task that requires careful planning and preparation. It is a big job that can transform your backyard, but it is important to get it right the first time as replacement is costly and difficult. Before beginning, it is essential to consider the size, situation, time and budget for your project. This will involve deciding on the area you wish to cover, whether you will excavate by hand or hire equipment, and the thickness of your patio slab. Once you have marked out your work area, you will need to excavate the site, assemble and level forms, mix and pour concrete, and finish the concrete. This process requires a range of tools and materials, including lumber for forms, concrete mix, and a cement mixer if you are mixing your own concrete. It is also important to consider adding reinforcement to minimise patio cracking. Overall, pouring a concrete patio is a complex process that requires careful planning and execution to ensure a successful outcome.

Excavate the area

Excavating the area is the first step in preparing the ground for your concrete patio. Here's a detailed guide on what you need to do:

• Mark the Work Area: Before you start digging, use spray paint, batterboards, or strings and stakes to mark out the area for your patio. Make sure to allow for an extra 18 inches around the length and width of your desired patio size. This extra space is necessary for the forms and working area.
• Dig Out the Soil: Use a shovel or a rented mini-excavator to remove the sod and topsoil from the marked area. Dig down approximately six to eight inches below the current soil level. The depth of your excavation will depend on the thickness of your concrete slab and any additional layers, such as gravel or mortar.
• Compact the Soil: Once you've dug out the area, compact the exposed soil surface. You can use a hand tamper or rent a compacting machine for larger areas. Compacting the soil creates a stable base for your concrete patio.
• Check for Level: Ensure that the excavated area is level by using a level tool or laser level. This step is crucial to ensure your patio slab will be even and stable.
• Add a Gravel Base (Optional): In areas with poor drainage or freezing temperatures, it is recommended to place a gravel base. Spread gravel in 2-inch layers, compacting each layer before adding more. The total gravel base should be 4 inches deep. Make sure to compact the gravel base thoroughly and check its thickness with a homemade template extending down from the tops of the forms.
• Prepare for Drainage: To prevent rainwater from pooling on your patio, design a slight slope. For every 10 feet in length, the patio surface should drop by about 2.5 inches. This slope will allow rainwater to drain off effectively.

Remember, proper excavation is essential for the success of your concrete patio project. Take your time and ensure that the area is level, well-compacted, and prepared for proper drainage before moving on to the next steps of building your concrete patio.

Create a form

The first step to creating a form is to join 2x6 or 2x8 lumber to form the outer shape of your patio. Use #10 x 3-1/2-inch deck screws to join the corners, with three screws per corner. If your patio is large, you may need to splice boards together. If so, butt two boards together and cut a strip of 1/2-inch plywood, nailing it across the joint. You will also need to attach a stake to each end of the plywood strip.

Next, you need to square the form. If opposite sides of your form area are the same length (which they should be), then equalizing diagonal measurements taken corner to corner will automatically make the corners square. Drive a stake into the ground at each corner to hold the form square.

Now, straighten the form. Lumber rarely comes perfectly straight, so you will need to use strings along the sides of the form as a straight reference line. Place stakes every 36 inches along the outside face of the form to hold the edges straight.

Then, level the form. Decide on the highest corner you want for your patio and raise the top of the form to that level. Drive a deck screw through the stake and into the form to lock it in position. This is your starting reference point. Now, use a 48-inch level or a laser level to raise the entire perimeter of the form to a level height. Double-check that the entire top edge of all form boards are level with each other.

Finally, saw the stakes. When it comes time to level your concrete, you will need to draw a long, straight piece of wood across the top edges of the form. This is called "screeding", and you will need to saw the stakes flush with the top edges of the form to make this possible.

Add reinforcement

Adding reinforcement to your concrete patio is an important step to ensure its longevity and prevent cracking. Here are the steps you should follow:

Firstly, decide on the type of reinforcement you will use. You can choose between concrete reinforcing fibres, steel mesh, or rebar. For larger projects or if you want to ensure maximum durability, it is recommended to use 1/2-inch rebar in a 12-inch by 16-inch grid.

Next, prepare the reinforcement for placement. Cut the rebar to size, if necessary, and shape it to fit the form of your patio. Place the rebar or mesh on wire supports so that it sits roughly in the middle of the slab's thickness. Ensure there is a few inches of space between the reinforcement and the edges of the form to prevent rust. Overlay sections of mesh by 4 inches and tie them together with wire.

Now, carefully place the reinforcement into the form. You want the reinforcement to be two inches off the bottom, so it is crucial to properly level and position it. Use additional wire or supports if needed to hold it in place.

Finally, check that the reinforcement is correctly positioned before proceeding with the concrete pour. Ensure it has not shifted and is still at the desired height. With reinforcement in place, you are now ready to pour the concrete.

Remember, proper reinforcement is key to a strong and long-lasting concrete patio. Taking the time to do this step right will pay off in the long run.

Pour the concrete

Now that you've done the hard work of preparing your site, it's time to pour the concrete. This is a critical step, so make sure you have all the necessary tools and materials ready before you begin. If you're working on a small project, you can mix the concrete yourself and pour it into the forms. However, for larger patios, it's recommended to use a ready-mix concrete delivered by truck.

Start by placing the concrete in one corner of the form. Use a shovel or hoe to spread it into the corners and against the forms and expansion joints. It's important not to overwork the concrete at this stage, as it can cause defects in the finished surface. Work in batches, placing each batch against the previous one to fill the form gradually. If you have a helper, they can use a shovel to spread the concrete while you work from the other side of the form.

Once the concrete is in place, use a straight piece of wood, such as a 2x4, to screed or level the surface. Pull the screed across the form, tilting it slightly and sliding it from side to side as you move forward. This will help to smooth out any bumps and ensure an even surface. If you need to fill in any low spots, shovel in some extra concrete and screed again.

After screeding, use a bull float to further smooth and compact the concrete. For small surfaces, a darby or a magnesium hand float can be used instead. Work the concrete until water forms on the surface.

The next step is to round the edges of the patio. Use a pointing trowel to separate the concrete from the forms, then run an edger along the forms to create a smooth, curved edge that will resist chipping.

To control future cracks in the concrete, you'll need to create control joints. Mark the forms every 8 feet and use a jointer to cut shallow grooves, known as control joints, in the wet concrete. These weakened spots will encourage cracks to form along these lines if the ground shifts.

Finally, after any water sheen has disappeared from the surface, use a wood or magnesium hand float to smooth the surface one last time. For improved traction, you can use a stiff-bristled broom to create a pattern on the concrete.

Level and finish the concrete

Once you've poured the concrete, you'll need to level and finish it to create a smooth, even surface. Here are the steps you should follow:

• Use a screed: With a helper, pull a screed (a long, straight 2x4) across the forms to level the concrete. Tilt the screed forward and slide it from side to side as you push it forward. Shovel off excess concrete in front of the screed or fill in any low spots. Make a second pass with the screed tilted in the opposite direction.
• Use a bull float: Work a bull float back and forth with the blade flat against the surface to smooth and compact the concrete. For small surfaces, use a darby instead of a bull float. Continue working the concrete until water forms on the surface.
• Round the edges: After floating, separate the concrete from the forms by running the tip of a pointing trowel between the two. Then, slide the cutting edge of an edger along the forms to round over the patio edge, making it less likely to chip.
• Cut control joints: Cut shallow grooves, called control joints, in the wet cement pad. These weaken the spots slightly so that if the ground shifts, the resulting crack should form along the control joint. You'll need a joint every 8 feet, so make marks every 8 feet along the forms.
• Float the surface again: After cutting the control joints and when any water sheen has left the surface, run a wood or magnesium hand float over the surface to provide a final smoothing. Raise the leading edge of the float slightly as you work to avoid making lines on the surface of the concrete.
• Create a non-slip surface (optional): For improved traction, pull a stiff-bristle broom across the surface. Draw the broom in straight or wavy lines. If you don't like the pattern or if it's too coarse, you can trowel, wit, and broom again. The longer the concrete dries, the finer the broomed surface will be.
• Cover the concrete: Lay plastic sheeting over the finished surface to trap moisture and eliminate the need for watering during the curing stage.
• Let the concrete cure: Let the concrete cure for at least 48 hours before removing the form boards. Keep the concrete moist during the curing process to prevent it from drying out too quickly, which can weaken the slab.

Frequently asked questions