Creating Concrete Patio Furniture: A Diy Guide

Concrete is an excellent material for building patio furniture. It is long-lasting, eco-friendly, water-resistant, and easy to clean. Concrete patio furniture can be made using a combination of moulds and concrete. The process involves creating a mould, preparing the concrete mixture, filling the mould, and allowing the concrete to cure. The type of furniture created can range from benches, coffee tables, side tables, stools, and even fire pits. Concrete furniture is a durable and stylish alternative to traditional patio furniture, providing a unique and modern look to your outdoor living space.

Characteristics of Concrete Patio Furniture

Prepping your mould

The first step in making concrete patio furniture is preparing your mould. This process will vary depending on the type of furniture you are creating, but there are some general steps you can follow.

If you are using a plastic chair frame, seal any holes with old magazines, duct tape, and hot glue. Tape off any larger openings or gaps with duct tape. You can also use an Ikea Vago chair as a mould, taping up the back and seat of the chair. Alternatively, you can create your own mould by using a large sheet of melamine and cutting out the desired shape with a jigsaw. Build up the sides of the mould with a vinyl wall base and attach it with construction adhesive and a staple gun. Fill in any seams with finishing paste wax and seal the corners with silicone caulk.

Once your mould is prepared, you will need to mix your concrete. For a concrete chair, cut rebar into four pieces, two 2-foot-long pieces, and two 1-foot-long pieces. Cut galvanized metal mesh to fit the width of the chair, and cut a hole for the drainage pipe. For a concrete table, you will need a slab of concrete board and wood for the base and legs. Cut the concrete board to size and screw pieces of wood to each side to create a border for the concrete.

Now you are ready to start filling your mould!

Mixing concrete

When mixing your own concrete, you will need the following ingredients: Portland cement, sand, gravel, and water. The basic recipe for concrete is 1 part Portland cement, 2 parts sand, 3 parts gravel, and 1 part water. However, you may need to adjust this ratio depending on the consistency of your mixture. If the mixture is too tough to make a groove, add more water. If the groove caves in, add more dry ingredients.

It is important to use clean water that is free of acids, alkalines, and oils. Always mix your concrete in a well-ventilated area and wear protective gear, including waterproof gloves, boots, a mask, and eyewear. To easily transport your concrete mixture, consider mixing it in a wheelbarrow.

Additionally, when working with concrete, it is crucial to follow safety precautions. Concrete is caustic, meaning it contains chemicals that can irritate or burn your skin. Always wear protective gear and avoid working in poorly ventilated areas. Use your legs when lifting heavy concrete to reduce strain on your back, and wear knee pads for comfort when kneeling for extended periods.

Filling the mould

Now that your mould is ready, it's time to fill it with concrete! Here are the steps you need to follow:

Prepare your concrete mix: Following the instructions on your concrete mix, prepare the desired amount. You can do this by hand or use a drill with a mixer bit for larger batches. Aim for a cooked oatmeal consistency. If it's a hot day, consider adding ice to your mix to slow down the curing process.

Add reinforcement (optional): If you want to reinforce your furniture, cut some galvanized metal mesh to size and place it in the mould before filling it with concrete. This will provide extra strength to your piece. You can also use rebar for reinforcement, especially if you're making a larger piece like a table. Twist the rebar and metal mesh together and elevate them in the mould so they're suspended in the concrete.

Fill the mould: Start filling your mould with concrete. Use a trowel or a piece of scrap wood to push the concrete into the corners and smooth it out. Work in small sections if your mould is complex. Tap the sides of the mould gently as you fill it to remove any air bubbles.

Vibrate the mould: To ensure that the concrete fills all the crevices and corners of your mould and to release any remaining air bubbles, vibrate the mould. You can do this by simply tapping or shaking the mould, or you can use a power tool like a random orbital sander to vibrate the mould more effectively.

Level the concrete: Once your mould is filled, use a straightedge or a 2x4 to level the surface of the concrete. Make sure it's even with the top of the mould. Be careful not to overwork the concrete at this stage.

Cure the concrete: Cover your mould with a tarp or plastic sheet to retain moisture and let the concrete cure for at least 48 hours, or as recommended by the concrete manufacturer. The curing time will depend on the size and thickness of your piece.

Remove the mould: After the concrete has cured, it's time to remove the mould. Carefully pry or peel away the mould from the concrete, using a screwdriver or a circular saw if necessary. Be very gentle, especially if your concrete is still "green" (freshly cured).

Smooth and finish: Once the mould is removed, use an angle grinder or sandpaper to smooth out any rough edges and give your piece a finished look. You can also apply a concrete sealer at this stage to protect your furniture from stains and the elements.

Smoothing and finishing

Once you've poured and levelled your concrete, you can begin the smoothing and finishing process. This involves several steps and techniques to ensure a flawless, durable finish. Here is a detailed guide:

• Bull Floating: Use a rounded bull float, a flat long-handled tool, to smooth out the surface of the concrete and embed aggregate particles further into it. Move the bull float back and forth across the slab, perpendicular to the direction you moved the levelling board. This will bring the smoother "cream" consistency concrete to the surface for better finishing.
• Edging: Use an edging tool to create level edges and tidy up the corners of your concrete. Move the tool in a back-and-forth motion in a 1- to 2-foot area before moving on. This will create more durable edges and improve the appearance of the concrete.
• Cutting Control Joints: Cut grooves, or control joints, into your concrete to direct the inevitable cracking and minimise the impact on appearance and functionality. These grooves should be cut to a depth of about 25% of the concrete's thickness and spaced no more than 24 times the thickness of the slab apart.
• Trowelling: You can use a magnesium trowel to create a very smooth finish. Pass the trowel over the slab two to three times, waiting for the concrete to dry slightly between passes, and lifting the leading edge a little more each time.
• Broom Finish: Dip a medium-stiff shop broom into a bucket of water, then shake off the excess. Drag the broom gently over the concrete in segments, overlapping each previous segment to ensure full coverage. This will create a non-slip surface.
• Curing: The final drying process of concrete takes several weeks, and proper curing minimises the chance of future damage. Cover the concrete's surface with plastic sheeting and weigh down the edges with heavy objects. Alternatively, keep the concrete wet by spraying it with water.
• Sealing: After the concrete has cured for at least a month, use a concrete sealer to protect it from liquid damage and make it easier to clean. Ensure the concrete is completely dry and clean before applying the sealant thinly to avoid puddles. Wait a few hours, then apply a second layer perpendicular to the first if needed.

Removing the mould

For a simple mould, such as a bucket, you can simply flip it upside down and chip away the plastic until it peels off the concrete.

For more complex moulds, you will need to pry off the mould with a screwdriver. If this doesn't work, you may need to use a circular saw to cut away the mould. Set the blade to 1/8 of an inch deep and use wrenches as spacers to avoid nicking the concrete surface.

Once the mould is removed, use an angle grinder to smooth any rough edges. Be very careful during this process, as the concrete will still be in a green state and quite fragile. It will take about a week for the concrete to harden and about four weeks to reach full strength.

Frequently asked questions