Building A Concrete Block Patio: A Step-By-Step Guide

Building a concrete block patio is a great way to create a stylish and functional outdoor space. While it may seem like a daunting task, it is actually a project that can be completed by beginners with limited concrete experience. In this article, we will provide a step-by-step guide on how to build a concrete block patio, covering everything from site preparation to laying the concrete blocks and even adding some decorative touches. We will also offer tips and tricks to make the process easier and help you avoid common mistakes. So, whether you're looking to improve your outdoor living space or just want to try your hand at a fun DIY project, follow this guide and you'll be on your way to enjoying your new concrete block patio in no time!

Site preparation

Firstly, determine the exact location of your patio and mark out the boundaries. This will involve driving stakes into the ground to define the dimensions. Work around any permanent fixtures like pipes, steps, or posts. Outline the perimeter by wrapping string around the stakes, pulling it taut to create straight lines.

The next step is to excavate the site. The depth of excavation will depend on the height of your concrete blocks and the required base materials. Typically, you should dig out the soil to accommodate the height of the blocks and leave an additional 5 inches for the base materials. For example, if using a concrete patio, you would dig out a space 8 inches deep: 4 inches for the concrete, 2 inches for mortar and brick, and another 2 inches for the base. Make sure to remove all sod and plant material from the site to prevent weeds from growing between the blocks.

It is important to grade the excavated area slightly to create a slope that prevents water from pooling on the concrete after installation. The slope should be directed away from your house and any outbuildings. A grading of 1 inch for every 4 feet of the block-paved area is usually sufficient for effective drainage.

Once you have completed the excavation, spread a layer of gravel over the area. The recommended depth for this layer is 4 inches. Level the gravel, following the initial grade, and then cover it with a 1-inch layer of sand. This will create a sturdy base that prevents the concrete from settling and becoming uneven over time. It also acts as a weed barrier. Tamp down the gravel and sand layer with a plate compactor before laying the concrete blocks.

Finally, install edge restraints to prevent the blocks from shifting or moving outward. You can use plastic or concrete restraints, setting them along the edges of the paved area and securing them with stakes.

Concrete block base installation

The concrete block base installation is a crucial step in creating a sturdy and durable concrete patio. Here is a detailed guide on how to install your concrete block base:

Firstly, prepare the site by removing any sod, plant material, or existing structures within the area. Ensure you have a slightly larger area to work with to make placing the forms and levelling the concrete easier. Use a flat-bladed shovel to clean the edges and smooth the bottom surface of the excavated area. The depth of your excavation will depend on the height of your concrete blocks and the required base material depth. For instance, if using 4-inch-high blocks, you will need to excavate to accommodate the block height and an additional 5 inches for the base materials.

Next, spread a layer of gravel over the excavated area. The recommended depth for the gravel layer is around 4 inches. Level the gravel layer, following the initial grade you established during excavation. You can use a plate compactor to tamp down the gravel and ensure a solid base.

Once the gravel base is prepared, it's time to add a layer of sand. Spread a 1-inch layer of sand over the gravel and level it. You can use a screed or a straight 2x4 to level the sand and ensure it is smooth.

At this stage, you can add edge restraints to prevent the blocks from shifting or moving outward over time. These restraints can be made of plastic or concrete and are locked in place with stakes.

Now, you are ready to start laying your concrete blocks. Place the blocks close together, leaving a maximum gap of 1/4 inch between them. Some blocks have interlocking edges, making spacing easier, while others with flat edges require careful placement to maintain even joints. If you need to cut blocks to fit specific areas, use a masonry saw or chisel and remember to wear protective eyewear.

After laying the blocks, use a plate compactor to ensure they are level. Then, pour sand over the entire area and sweep it into the joints between the blocks. You may need to add more sand over time as it settles. Using paver sand is recommended as it has a fine texture and helps lock the pavers in place.

Finally, you can apply a sand-binding sealant over the joints to prevent the sand from washing out and make cleaning stains easier.

Laying concrete blocks

Site Preparation:

First, clear the site of all sod and plant material to ensure the blocks remain level and prevent weeds from growing between them. The depth of the excavation should accommodate the height of the blocks with an additional 5 inches for the base materials. The excavated area should be level, with a slight grade to allow for drainage. The slope should be graded about 1 inch for every 4 feet of the block-paved area, sloping downward to prevent water from pooling on the concrete and direct it away from your home and any nearby outbuildings.

Concrete Block Base Installation:

Spread a layer of gravel over the excavated area to create a sturdy base. The University of Missouri Extension recommends a 4-inch layer of gravel, which should then be levelled and compacted with a plate compacter before laying the blocks. Cover the gravel base with a 1-inch layer of sand and level it as well.

Edging and Restraints:

Before laying the concrete blocks, it is essential to install edging and restraints to prevent the blocks from shifting or moving outward over time. Use plastic or concrete restraints along the edges of the paved area, locking them in place with stakes.

Laying the Concrete Blocks:

Place the concrete blocks close together, leaving no more than a 1/4-inch gap between them. Some concrete pavers have interlocking edges that make spacing easier, while others have flat edges that require manual spacing. Use a masonry saw or chisel to cut any blocks to fit, and always wear protective eyewear when cutting.

Compacting and Sanding:

Once all the blocks are laid, use a plate compactor to ensure they are level. Then, pour sand over the entire area and sweep it into the joints between the blocks. Paver sand is recommended as its fine texture helps lock the pavers in place. You may need to add more sand over time as it settles.

Additionally, you can apply a sand-binding sealant over the joints to prevent the sand from washing out and to facilitate stain removal.

Pouring concrete

Before pouring the concrete, you must prepare the site properly. First, remove any existing sod and scrape, rake, and shovel the patio area to make it as level as possible. Depending on the grade and the finished height of your patio, you may need to add some sand fill. Next, lay out the patio's footprint with stakes and string, ensuring the math works out and that the footprint is square. Then, assemble and stake the forms in place, using 1-by stakes between the 2x4s. Lift and adjust the form to make it level, then screw it to the stakes. Once you're satisfied, cut the stakes flush with the top of the form. Cover the gaps between the 2x4s with duct tape to prevent them from filling with concrete, and fill in sand up to the bottom of each paver space to prevent the concrete from flowing underneath the form.

Now, you are ready to pour the concrete. If you are using a wheelbarrow, build a temporary ramp over the forms so that the wheelbarrow won't knock them out of place. Start in a corner and dump the loads of concrete against each other. Have a helper spread the concrete into corners and against the forms and expansion joints using a shovel. Lay a wide board across the forms so you can reach the interior of the pour. If the concrete covers the wire mesh, pull it up with a rake so that it's in the middle of the slab. Work a shovel or rake up and down to remove air pockets, especially alongside the forms.

After pouring the concrete, "float" the surface. Once the bleed water has disappeared, float each section with a magnesium float. Floating embeds coarse aggregate particles and smooths the surface without sealing it. After the concrete begins to stiffen, round over the edges of the pavers with a special edging tool. You'll need to work quickly, as there will be a lot of edging to do. When you're able to kneel on kneeboards on the concrete and only leave a 1/8- to 1/4-inch deep indentation, start troweling the pavers. Troweling makes the surface hard, dense, and smooth. Put a little "spring" in the trowel to increase this effect and feather out the transition created by the edger.

Sealing concrete

Sealing a concrete patio is a great way to prolong its life and improve its appearance. It is important to seal concrete properly, as it can be prone to fading, discolouration, and abrasion from foot traffic, weather, and other sources of wear and tear.

Firstly, you need to ensure the concrete is clean and cured. Sweep the surface to remove dirt and debris, and use a degreaser to remove any grease or oil. If there are any residual coatings, such as mastic, use a putty knife and a stiff brush to scrape it off, then apply a citrus-based cleaner. After removing stains, mop the surface with floor cleaner and water, and use a shop vacuum to remove any remaining water or debris. Allow the concrete to dry for 24 hours.

If your concrete has any cracks or pitting, fill them in with a concrete crack sealer and smooth over with a putty knife. If your concrete has been sealed before, you will need to remove the old sealer. You can do this with a chemical stripper, but be cautious as these are acid-based and can damage concrete if used incorrectly. Apply the stripper with a roller or handheld airless paint sprayer, then scrape the surface to remove the sludge. Clean the surface with trisodium phosphate (TSP) and water, then vacuum up any remaining water and let it dry for 24 hours.

Now you are ready to apply the new sealer. If your concrete is new, wait at least one month before applying sealer. The temperature should be above 50°F during application and drying, which can take up to three days. Apply the sealer with a roller or sprayer, working in sections and in thin, even layers. Avoid creating puddles. Apply two thin coats, waiting at least two hours between coats.

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