Creating Better Decorative Concrete
There are a large number of good decorative concrete projects out there. However, with just a bit more effort these jobs could have been great. Attention to detail can turn ordinary stamped concrete into something better. The average customer looking at stamped concrete may not be able to pinpoint exactly why he prefers one project over another, but it is probably because one contractor paid more attention to detail.
Stamped concrete is intended to mimic natural stone, brick, slate, etc. It is therefore 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. However, good formwork, the right color choices, detailing the joints, 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 concrete project, but is absolutely essential in decorative concrete. If the formwork was hurried, the job will usually suffer. For instance, if the edges of a slab are intended to be straight, 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 formork 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 in such a way that the splice is not evident as a defect in the finished product. In other words, 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 repairing things later.
- Color is one of the most subjective aspects of stamped concrete. 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 inadvertantly contribute to a fake-looking job. For instance, if a customer chooses a fieldstone pattern but picks colors that do not resemble real fieldstone, the job probably won’t fool anyone. Realism is not always the aim of stamped concrete, however. Sometimes customers just want something unique. Customers who do expect realism should try to choose a stamp pattern that complements their color choice. Experienced contractors have usually seen many color combinations and should be able to guide their customers in the right direction.
- Detailing the joints is perhaps one of the most neglected aspects of stamped concrete. There are several drawbacks that result from failure to detail. For example, when two adjacent stamps are embedded into the surface, there is often soft material called “squeeze fins” that comes up between them. If this material is not dealt with, it shows up in the finished product as a discolored or protruding ridge. Squeeze fins can be eliminated while the concrete is still soft by using joint rollers to push them down. However, sometimes the concrete is setting up too quickly to allow time for rolling the joints while stamping. In this case, hardened squeeze fins should be removed with chisels or a grinder after the concrete has set. Neglecting to remove sharp squeeze fins can result in injury as the fins come in contact with bare feet.
Other cosmetic problems can occur if the contractor is careless and fails to align his stamps properly. Improperly aligned stamps result in double-stamping, overlaps, or stamps failing to butt up against one another. In the latter case, there are no squeeze fins because the stamps are too far apart. Instead, the resulting joints are much too wide and don’t match the narrower joints elsewhere in the pattern. When this happens, there is little that the contractor can do except try to patch the slab with a topping compound and fake the joints in later. It is very difficult to patch stamped concrete and get a good color match, so while they are stamping contractors should be certain that they keep the stamps well-aligned.
A further consideration with stamped joints is that they should reach all the way to the edge of the concrete or up to a wall. They should not be allowed to simply stop near the edge. Stamped joints can be continued to the edge by using chisels or joint rollers. Not continuing joints to the edge is simply careless on the part of the contractor. It is one of the biggest culprits in making a job look fake. Real stones don’t just stop or fade into nothingness. If the joints are not placed while the concrete is still workable, then they should be ground in later
When detailing, another type of joint to consider is the crack control joint (often mistakenly called an expansion joint). Crack control joints are either tooled or sawed joints designed to control random cracking. They should be carried all the way to a wall or to the edge of a slab. Not only does an unfinished joint look bad, but it dams up water that should be allowed to drain from the slab. If joints are not opened up so that water can drain off the edge, the joint will hold rainwater which may cause problems in a freeze.
If saw-cut crack control joints are not continued all the way to a wall, the resulting crack will continue from the end of the cut to the wall. That few inches of random crack looks bad: 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 four inch angle grinder equipped with a diamond blade is small enough to finish the cut.
- Step risers and other vertical surfaces are sometimes overlooked or treated as an afterthought. Often, the horizontal surfaces are patterned, whereas the vertical surfaces are only colored. This contributes to a less-than-realistic job. If real stones or bricks were laid atop a step, you would see their sides on the step face. Therefore, a stamped pattern or texture shouldn’t just stop at the edge of a slab. It should continue down the face, just as if the project were constructed from real stone or brick. Step risers and verticals deserve just as much attention as the rest of the project.
There are several ways to pattern and texture a vertical surface. One method involves attaching manufactured form liners to the inside of the forms. When the concrete is poured into the form, it takes the shape of the liner and makes the sides of the concrete resemble the stamped top.
Some contractors like to remove the step forms while the concrete is still semi-soft and stamp the pattern then. This is an option, but timing is everything. Great care must be taken to avoid causing the step to slump because it was stripped too soon. Simply getting to the steps can sometimes require that the stampers go back out on an already stamped slab. This re-entry creates the potential for marring or discoloring the slab’s surface.
Another method involves stripping the forms after the concrete has set. Then a colored paste is applied to the exposed concrete face and subsequently textured (this is called parging). Often, the entire step face doesn’t need to be treated. Simply creating a bullnose and coloring only that can make a step look more finished. No matter how it is accomplished, a colored, textured, and patterned step face looks better than a flat one.
- The over-application of concrete sealer is another thing that makes a job look unnatural. The more sealer that is applied, the shinier and more slippery the concrete gets. Too high a buildup of sealer makes the concrete look like plastic, and does no better at repelling moisture than a thin coat would. Although many contractors are guilty of applying too much sealer, the bigger problem may be the homeowner who re-coats his patio every year to keep it looking shiny and new. Over-applying sealer is one of the most common mistakes in stamped concrete, and can cause more problems than just a shiny surface. For more on over-sealing stamped concrete, please read the articles entitled “Should I Reseal My Concrete” by clicking here and “Xylene and Stamped Concrete” by clicking here.
One of the best ways to turn an ordinary stamp job into something more is to individually tint some of the stamped “stones”. The tinting can be done with acid stains, pigmented stains, antiquing solutions, etc. No matter how it is done, using a few extra colors throughout a project can provide curb appeal that can’t be matched by using only a base color and an antiquing color.
Simple attention to detail is one of the surest ways to produce better stamped concrete. When a contractor’s work improves, his business generally follows suit. Conversely, contractors who fail in this regard will lose work to those contractors who do pay attention to detail.