There are many good decorative concrete projects out there. However, with just a bit more effort, these jobs could have been great. Paying attention to the details can turn ordinary stamped concrete into something better. While the average customer looking at stamped concrete may not be able to pinpoint exactly why he prefers one project over another, it is probably because one contractor paid more attention to the details.
Stamped concrete is intended to mimic natural stone, slate, and brick. Therefore, it is the contractor’s job to make it look as realistic as possible. Small details can often make or break a job. Let’s face it: Some stamped concrete can look fake. But good formwork, the right color choices, detailing the joints, creating realistic step risers, proper concrete sealing, and individually coloring some stones can all differentiate an adequate stamped job from one that “wows.” Let’s look at these factors individually.
Good formwork is extremely important to the outcome of any project, but it is absolutely essential in decorative concrete. If the formwork was hurried, the job will usually suffer. If the edges of a slab are intended to be straight, then formwork should be well-braced so it doesn’t bow out or become wavy when concrete is placed against it.
Corners should be squared so the stamped pattern can be properly aligned with the edge of the slab. Because many stamp and stencil patterns are rectangular, out-of-square formwork creates stamped bricks or stones that get progressively smaller along the edge of the form. Wedge-shaped stones are a telltale sign that something is not right.
Likewise, if a curved edge is needed, the forms should exhibit a clean radius without bulges. Form boards should be joined together so that the splice is not evident in the finished product. The forms should be butted together and spliced on the back side rather than being overlapped to create an impediment to the edging tool. Forming the right way initially may take a bit longer, but it results in a cleaner looking job and saves the headache and expense of later repairs.
One of the most subjective aspects of stamped concrete is color. Everyone has different tastes, but most can agree on what looks real and what doesn’t. Customers often get so caught up in deciding which color matches their home that they fail to consider which one looks best with their chosen stamp pattern.
By choosing the wrong color, they may inadvertently contribute to a fake-looking job. For example, if a customer chooses a fieldstone pattern but picks colors that do not resemble real fieldstone, the work probably won’t fool anyone. A customer who expects realism should try to choose a stamp pattern that complements his color choice and the contractor should encourage this.
Detailing the joints
One of the most neglected aspects of stamped concrete is detailing the joints. Failing to detail can create cosmetic problems, but in extreme cases, it can even be dangerous.
When two adjacent stamps are embedded into the surface, there is often soft material called squeeze that pushes up between them. If not dealt with, this material shows up on the finished slab as a protruding ridge or fin. If not removed, sharp squeeze fins can injure bare feet.
The simplest way to eliminate squeeze fins is to use touch-up rollers to push them down while the concrete is still soft. But sometimes the concrete sets up so quickly, there is no time to detail the joints while stamping. If this occurs, remove hardened squeeze fins later with chisels or a grinder, and then re-color them to match the rest of the stamped joints.
Stamped joints should not only be clean, but it is also important to make sure they reach all the way to the edge of the concrete or up to a wall instead of simply stopping near the edge. Stamped joints can be continued to the edge by using chisels or touch-up rollers. Failure to complete a joint is simply careless on the part of the contractor, and is one of the biggest culprits in making a job look bad. Real stones don’t just stop or fade into nothingness, and neither should stamped ones.
Another type of joint to consider is the contraction joint, which is somtimes mistakenly called an expansion joint or control joint. Contraction joints are either tooled or sawed joints designed to control random cracking. Like stamped joints, they also should be carried all the way to a wall or to the edge of a slab. Not only does an unfinished joint near the outside form look bad, but it can also hold water that would otherwise drain from the slab. If joints are not opened up so that water can drain off the edge, they will hold rainwater which may cause problems in a freeze.
If saw-cut contraction joints are not continued all the way to a wall, the resulting crack will continue anyway. That random crack is ugly; a sawed joint would look much cleaner. Although concrete saw blades are too large in diameter to cut all the way up to a wall, a 4-inch angle grinder equipped with a diamond blade is small enough to finish the cut.