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Summary: If you are one of the 1000's of home owners who are planning to build a patio this year, you can do something a bit different from the old familiar brick or plain concrete patio and have a functional conversation piece during the months you use it and beyond. It is easily assembled from custom cast modular blocks and the texture is achieved by pressing a layer of course aggregate into the concrete while it is still wet.
First off, check with your local laws to see if you need a permit to add a patio and if there are any restrictions involved. Once you know what you are allowed to do, you can prepare the foundation to lay your blocks. There are many ways to prepare a patio foundation which are beyond the scope of this article, but basically, make sure that the site is level and properly prepared before laying your completed blocks.
Before you begin the actual work of casting the blocks, draw out your patio plan on a sheet of graph paper. Be sure it is complete with the sizes and shapes of the blocks you would like use, as well as the placement of the blocks to create the design. If you are also measuring with your graph paper, subtract 1/2 inch for the joint between each module for the mortar. You are not limited to rectangles and squares, but can use any shape that you feel you can build a form, or mold, for. But with just 3 different dimensions of rectangular blocks, there are hundreds of possibile ways to arrange them. For simplicity, this article will assume the blocks are rectangles.
Once you have determined the dimensions of the various blocks, you will need to make up two forms for each size block out of stock or scrap lumber. Simple nailing of overlapping corner joints is sufficient; these frames aren't meant to win woodworking contests. The first form should have sides that are 1.75 inches high and must be .25 inches smaller on all sides than the finished dimension of the block.
The sides of the second form should be 2 inches high and the internal dimensions must match the desired outside dimension of the block. This two form system is what makes it possible to level the concrete before adding the aggregate.
The aggregate can be anything you want, from various sizes of smooth or coarse stones, flagstone chunks, broken tile chips for a random mosaic of one or many colors, to tumbled and smoothed bits of colored glass. Experiment with your imagination! There are many things that can be used for a patio or stepping stone aggregate. Even large pieces of wax can be pressed into the concrete that you can melt away to leave holes in the shape of the wax; this leaves interesting designs when filled with rain water or planted with grass or moss. For simplicity, this article will assume that the aggregate is a colorful batch of small, smooth, beach pebbles that are roughly about an inch in size.
For safety sake, make sure to wear gloves while you are working with cement, either wet or dry. Start with a mixture of 1 part cement, 2 parts sand, and 2 parts pea gravel that has been well blended. You can also purchase a pre-mixed bag of cement that you just add water to. Moisten the mix to the consistency of mortar and pour it into the smaller form you have made, filling it. Firmly tamp and level it in this smaller mold.
After tamping, vibrating and screeding, which is another term for settling and smoothing, allow the mixture to harden sufficiently to lightly retain its shape, Then remove the frame of the first mold from the block by carefully lifting the front edge of the frame and sliding it to the back before lifting the entire frame. Carefully put the second one in its place by using a similar motion, and center it.
Spread your chosen aggregate evenly over the surface of the moist concrete. The pebbles that make up the aggregate should all be approximately the same size.
Level the aggregate by shaking the frame a little bit and press it into the moist concrete with a hand tamper. You will be pressing it until it is level with the 2-inch sides of the mold.
When the concrete has set sufficiently to retain its shape, remove the second form from the block by carefully lifting the front edge of the frame and sliding it to the back before lifting the entire frame. Allow the block to dry completely before installation. Do not let the cement dry while in the frame because you will not be able to free it.
After you have all your blocks created and they have dried completely, you can assemble the various modules according to the plan that you previously decided on from your graph paper design. Be sure to leave a half inch between each modular block for the addition of mortar, not cement, to complete your patio. Instructions for how to mortar your blocks is beyond the scope of this article.
You may have already figured out that these blocks are not just for patio floors. You can use them to create walkways or simply make unique stepping stones. You can even use them to make a decorative block wall attached to an existing wall or even hide a ugly fence.
You aren't limited to any shape or any size or thickness either. Just make sure you make 2 frames when doing aggregate work. You will only need to make 1 frame if you are using other methods of decorating concrete such as pressing different diameters of cans into the moist surface, or using cookie cutters for the same purpose. You can even use a stiff brush to make a combination smooth vs brushed pattern on the same stone. Just use your imagination and have fun!
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