Q: I am a California architect and read your article about decorative concrete at the World of Concrete. Are there processes that can be used on existing concrete floors to make them more decorative? I know you can use dyes and then stamp it with wet concrete. Is there a polishing process using dyes or something similar that might accomplish this? I would like to incorporate decorative concrete on commercial and residential remodeling projects.
A: Polishing a concrete surface reveals the beauty that is within the concrete. Because it exposes the concrete texture just below the surface, the beauty of the polished slab relies on what is in it.
The most successful polishing projects begin with placing a very flat floor slab. If the existing floor is not fairly flat to begin with, significant amounts of grinding may have to precede the polishing. An alternative is to place a new layer of concrete atop the old slab and then do the polishing. That also provides the opportunity to include some colorful aggregate, for example, or to use colored concrete.
There are lots of other ways to achieve a decorative look. Many products and systems are available that have been developed specifically for use on existing concrete floors. On one end of the spectrum are stains and dyes that can be used to accent or completely change the natural look of the concrete. Sealers, with or without tinting, can improve appearance and provide an enhanced surface, including changing its traction characteristics. Materials for thicker applications include overlays and toppings. Many are designed for stamping to add patterns that give the look of other paving materials, such as brick or stone, while maintaining the durability of concrete. They also can be used to reprofile the floor.
You should keep a couple of things in mind as you consider this type of application. First, the concrete should be sound—free from large cracks, major spalling or other signs of distress. Although patching such problems may be possible, the repairs may end up showing through any decorative treatment you may add. To put that another way, a decorative treatment may end up drawing attention to the repair.
Also proper surface preparation is very important. The International Concrete Repair Institute (ICRI) has established guidelines for various surface profiles that are appropriate for different types of materials applied to concrete. Overlay manufacturers usually include a profile number with their directions, which indicates the degree of profile, or “tooth” the concrete needs for a successful bond and refers to the ICRI guidelines. ICRI shows 9 levels of profile, from an almost smooth 1 to level 9 where the profile is ¼ inch deep. In addition to its published “Surface Preparation Guide,” the organization offers a set of surface profile chips so you can see and feel what they mean for each of the levels of profile.
As you consider decorative treatments, remember to account for how much traffic the floor will see. Many decorative products are designed to hold up well under heavy traffic, but may require topcoating of some type to do so.
Another thing to keep in mind is the environment in which the decorative treatment will be applied. For example, an interior concrete floor in an older strip mall with a common air-handling system may not be a good candidate for applying acid staining. Fortunately, there are plenty of alternatives, but you do need to anticipate such secondary effects.
Manufacturers and distributors of decorative concrete products frequently offer training in the use and application of their products. Most often these are set up primarily for people who are or will be applying the company's products, but it sounds like you might benefit from participating in such an overview. Some firms in the past have made training sessions available for free to members of the design community, so that might be something worth asking about.
Of course there are many online resources available as well. For more ideas on decorative applications, see Decorative Concrete: The 2008 Artistry Demos on page 74.