Stamped concrete can imitate the texture and shape of individual stones. We use stamps to apply a texture, but in order to create a pattern (tile, stone, or other) there are a few methods we can use. The first option is to use a stamp that already has a pattern in it to transfer it to the overlay material while it is still soft. The stamps, apart from the stone texture, could have a tile pattern, a random stone pattern, an ashlar slate pattern, etc. These stamps come in sets of six to eight pieces that butt up one to the other in a specific way, repeating the pattern over and over again, kind of like pieces of a jigsaw puzzle that fit together in only one way.
Awesome! You get it all in one shot, but like everything in life it has its pros and cons. Yes, you get texture and pattern in one shot but it also means you need a set of stamps for each pattern, not just the texture. You can't use a stamp set that has a tile pattern if the client wants a random stone, or vice versa so you have to have a lot of sets and at almost $150 or more per individual stamp, it adds up quick. However, the biggest drawback isn't cost, it's how this type of stamp is used.
Let's return to the jigsaw puzzle analogy. Imagine if I handed you a puzzle with all the same shape pieces but told you that each piece would be glued down as you placed them, no moving them around. Now I tell you that you are going to put them down in order but skip over one section in the middle then come back and fill it in. You'd be nervous that if you didn't align everything perfectly when you came back to fill it in the pieces wouldn't fit, well it's the same case when we use a stamp that has both texture and pattern. In our case we are putting a pattern in a slowly hardening stamped concrete overlay material. We butt one stamp up to the other, transfer the pattern, then place the next one and so on. This keeps the pattern consistent throughout the area; but what happens if we have an area that isn't drying as fast as the others, maybe it's in the shade, or worse, one that is in the sun and is drying very quickly and we haven't been able to get to it? We can't just walk out there, drop the stamp on it, transfer the pattern, then walk back to where we were doing our work; will it line up? Of course not, then one pattern will fall over the other instead of next to it and it all goes to pot.
The solution? Create patterns in the stamped concrete by waiting for it to harden and then cutting, or scoring, it using a saw with a diamond blade. This way we can take all the time we need to cut elaborate or simpler designs. We can score a larger range of sizes and shapes such as square tiles, diamond tiles, random stone, and other patterns. The first step of the scoring process is to mark out the desired pattern. For a tile pattern we typically use chalk lines to create the guidelines. A chalk line is a thin string coated in powdered chalk. We stretch the string over the concrete and pluck it, transferring the chalk onto the concrete in a straight line. We use blue chalk which is easier to wash away instead of red as it is much harder to remove. If we were doing a random stone pattern we just trace it out on the stamped concrete using a piece of chalk.
Next, we use an angle grinder with a circular diamond-tipped blade to cut the stamped concrete. Diamond-tipped blades are metal blades with diamonds bonded to the edge. The metal part wears away during scoring, exposing new diamonds buried inside it which are what do the actual cutting. Straight, jagged, or curved lines can be scored into stamped concrete.
Parts of the pool deck at the Carrollton home ended at stone or brick walls. Usually, when a concrete layer edges against a wall, we leave an unscored, 8" border along the edge of the concrete; that way we don't end up cutting into the wall before finishing off the pattern as it comes up against it. However, in this case our homeowner did not want a border; he wanted us to continue cutting the random stone pattern in the floor right up to the wall. To do it we used a 4" circular diamond blade to get closer to the wall then switched to a Dremel to cut the rest of the way. It worked like a charm. We wrapped it up by using stains to create different colors to the individual stones. Next, we will talk about the various ways to apply color to stamped concrete.