Pouring Concrete Patios: House Foundation Techniques And Tips

Pouring concrete against the side of your house is possible, but there are some important things to consider. Firstly, it is recommended to install an expansion board or joint right up against the house to separate the patio from the house and allow for independent movement. This is especially important in areas with freeze/thaw cycles, as it can prevent damage caused by expansion and contraction. Secondly, proper preparation of the sub-grade soil and drainage is crucial to prevent the concrete from sliding or settling. Additionally, in some regions, such as Palm Beach County, Florida, drilling rebar into the existing slab is required by the County for approval. However, there are differing opinions on the effectiveness of this method, with some experts suggesting that proper soil preparation is more important. Overall, while pouring concrete against the house is feasible, careful planning and adherence to local building codes and recommendations are essential to ensure a successful outcome.

Expansion joints are relatively cheap and easy to install

Expansion joints are crucial to have between concrete slabs. They are relatively cheap and easy to install, and can be purchased at a home improvement store in various sizes.

Expansion joints act as a buffer between slabs of concrete, allowing them to move independently from one another. This is especially important when installing concrete against a stationary structure, such as a house, as it prevents damage to the concrete or the structure it parallels. Without an expansion joint, the concrete could cause excess stress on the house's foundation, which could lead to cracking or other issues.

To install an expansion joint, simply nail or screw the joint to the structure. If the structure is not wood, lay the expansion joint up against it and ensure that it remains flush with the structure as you pour the concrete. It's important to fill or seal expansion joints to prevent water from running through them, which can cause sinking, settling, or heaving of the concrete over time. You can use a flexible non-sag and/or self-leveling caulk to fill the joints, which will still allow the concrete to move and expand.

In addition to expansion joints, it is also recommended to have control joints in your concrete slab to help control the cracks that will eventually appear. These can be cut into the concrete after it has cured using a circular saw with a cement or masonry blade.

The concrete patio should slope away from the house

Constructing a concrete patio requires careful planning to ensure it effectively directs water away from your house. Here are some detailed instructions to help you build a concrete patio that slopes away from your house:

Planning and Layout:

Start by laying out the patio area using batterboards and a mason's line. Remove any existing sod or vegetation and dig out the soil to the required depth. The depth of excavation depends on the type of patio you're installing. For example, a concrete patio typically requires a depth of 8 inches: 4 inches for the gravel base, 4 inches for the concrete slab, and an additional 2 inches if you're using mortar and brick.

Next, drive stakes along the layout lines, positioning them at the corners and every 2 feet in between. These stakes will serve as a guide for the slope of your patio. The patio must slope away from the house, and the recommended rate is 1/8 to 1/4 inch per foot, or a minimum of 2% fall. Check your local building codes for specific requirements in your area.

Formwork and Slope Preparation:

After marking the desired height on the stakes, use a chalk line to snap a line across all the stakes, ensuring they are at the correct height for the intended slope. Align 2x4 boards with these marks and nail them in place to create the formwork. Cut the stakes so that they are flush with or slightly below the tops of the forms. This will ensure a smooth concrete surface.

For larger patios or those with longer sides, you may need to splice boards together. Butt two boards together and reinforce the joint with a strip of 1/2-inch plywood, nailing it across the joint. It is crucial to maintain the desired slope along the length of the formwork to achieve the correct patio slope.

Expansion Joints and Release Agents:

Before pouring concrete, install a 1/2x4-inch expansion joint against the foundation of the house and any existing concrete that meets the patio. This expansion joint will prevent the new concrete from bonding directly to the foundation, reducing the risk of cracking due to differential settlement.

Additionally, apply a release agent or vegetable oil to the formwork to prevent the concrete from sticking to the boards. Commercial release agents are available, but vegetable oil or motor oil can also be used. However, motor oil may not work as effectively and can contaminate the ground.

Pouring and Finishing Concrete:

With the formwork and expansion joints in place, you're ready to pour the concrete. Use a wheelbarrow to transport the concrete and start pouring in a corner, working your way out. Spread the concrete evenly and use a screed (a long, straight 2x4) to level the surface. Make multiple passes with the screed, tilting it forward and sliding it from side to side as you push it forward.

After levelling, use a bull float to smooth and compact the concrete further. For smaller surfaces, you can use a darby instead. Work the concrete until water forms on the surface, indicating proper finishing.

Curing and Final Touches:

Once the concrete is floated and levelled, let it cure. Cover the surface with plastic sheeting to retain moisture and promote proper curing. Allow the concrete to cure for at least 48 hours before removing the formwork.

After curing, you can add a final touch by rounding the edges of the patio with a pointing trowel and an edger. This step helps prevent chipping. Additionally, cut control joints in the concrete to create weak spots that will encourage cracks to form along these lines if any ground movement occurs.

By following these steps and ensuring the proper slope away from your house, you can create a durable concrete patio that effectively manages water runoff and protects your home's foundation.

You can use rebar to keep the patio from settling

When pouring a concrete patio, it is important to consider how to prevent the patio from settling. One effective method is to use rebar, which acts as an internal skeleton for the concrete and provides additional strength and stability.

Rebar can help keep your concrete patio from settling by distributing weight evenly and preventing cracking or settling. This is especially important if your patio will be subjected to heavy loads, such as furniture, planters, or vehicles. In addition, rebar can also help mitigate the effects of expansion and contraction due to extreme temperature fluctuations or freeze-thaw cycles, reducing the risk of cracking.

To use rebar effectively, it is recommended to place it in the middle of the slab's thickness. This can be achieved by using wire supports to hold the rebar in place before pouring the concrete. It is also important to ensure that the rebar is properly secured and does not stick up above the surface of the concrete, which can interfere with achieving a smooth surface finish.

When using rebar, it is also crucial to consider the size and spacing of the bars. For thinner patios, a thicker gauge rebar may be required to provide sufficient structural support. Additionally, placing multiple layers of rebar, one at the bottom and one at the top of the slab, can further enhance the patio's stability.

By incorporating rebar into your concrete patio, you can be confident that your patio will have a long-lasting structural integrity. Rebar is a proven method to prevent settling and cracking, ensuring the durability and longevity of your outdoor space.

You can pour the concrete in sections or all at once

Pouring concrete in sections or all at once depends on the size of the slab and the number of people you have helping you. If you're pouring a large concrete slab or only have a small team of helpers, dividing the slab into sections will give you more control over the pour and result in a more stable slab.

Each section you pour will be a separate slab surrounded by expansion joints on all sides. The expansion joints release tension, preventing cracks from forming when the concrete expands and contracts with temperature changes. The sections should not measure more than three times the slab's thickness. For instance, if using a 6-inch slab, the expansion joints should be set every 18 square feet at most.

If you feel comfortable with finishing concrete and have enough helpers, you can pour the entire area as one. However, if you're pouring a large slab and it starts to set up quickly, you may want to consider pouring in sections. This involves pouring each 10 x 20 foot section and then coming back a couple of days later to fill in the others.

Regardless of whether you pour in sections or all at once, it's important to prepare the ground properly and ensure you have the necessary tools and materials before beginning the project.

You can use a concrete edger to round the edges of the patio

Pouring concrete directly against the house is not recommended. Instead, it is best to use an expansion joint set against the wall, which can be made from cork, tar or asphalt. This will prevent the concrete from bonding with the house foundation and reduce the risk of cracking.

Once the concrete has been poured, you can use a concrete edger to round the edges of the patio. Concrete edgers are small trowels with one curved side, which create a neat, rounded edge along the slab perimeter. This helps to prevent chipping and spalling damage to the slab once the forms are removed. Edging should be performed after the bleedwater has disappeared from the concrete surface, but before the forms are removed.

There are two main types of concrete edger: hand edgers and walking edgers. Hand edgers require kneeling next to the slab and are available in sizes ranging from 1 1/2 to 6 inches wide and 6 to 10 inches long. Walking edgers, on the other hand, attach to a handle and allow the user to walk alongside the slab while edging. Walking edgers are useful for minimising bending and kneeling.

When choosing a concrete edger, consider the radius of the edge, the lip depth, and the handle type. The radius of the edge can vary from 1/8 inch to 2 inches, while the lip depth ranges from 3/8 inch to 1 1/2 inches. Hand edgers are typically made from wood, while walking edgers may have comfort-grip handles to reduce hand fatigue.

Prices for edgers vary depending on the quality of the blade, with blue-steel edgers costing around $5-6 and bronze or stainless steel edgers costing upwards of $25.

Frequently asked questions