A concrete overlay allows you to give a sound surface a decorative facelift. A cementitious material is mixed and applied directly over the existing concrete. Overlays can be colored in a variety of ways, polished for a reflective shenn, or used in conjunction with stencils and stamps. Certain products are designed for use on indoor floors, while others are made to
FACTORS TO CONSIDER WHEN CHOOSING AN OVERLAY SYSTEM
Selecting the most appropriate resurfacing system often involves weighing performance attributes against aesthetic value. Here are some questions to ask to help you find a system that will strike the perfect balance for the job at hand.
What is the condition of the existing surface?
Does the concrete have a lot of cracks or gouges? Is the surface out of level? If so, choose a higher-build material, such as a self-leveling or stampable overlay that can be applied at a thickness of 1/4 inch or greater. Unless the surface imperfections are expertly patched or filled, they could telegraph through a thinner overlay, such as a microtoppping or skim coat.
Too much moisture in the concrete substrate can also be a problem for some overlay systems, especially products that restrict the ability of the concrete to "breathe" or release moisture vapor as needed. There are simple tests you can perform to check the moisture vapor emission rate of concrete. If it's too high, be sure to use a permeable overlay system that will permit the moisture vapor to escape. (Read more about reducing bond failures caused by moisture vapor transmission.)
What conditions will the overlay be exposed to?
Be sure the topping or overlay system is tough enough to withstand all the conditions it will confront. Is the slab outdoors and subject to weather extremes and freezing and thawing? Is it a floor surface in a high-traffic area or subject to chemical, grease, and oil spills? Although most systems will stand up well to wear, chemical attack, and dirt penetration when properly installed and sealed, some are better suited than others for harsher exposure conditions. Often a higher-build material or a material containing aggregates will perform better in aggressive environments.
What is the installed cost?
The total cost of overlay installation will be higher if you are using stencils, stamping mats, or decorative engraving or sawcutting to pattern the surface. Using more than one coloring method (such as integral color combined with broadcast pigments and stains or dyes) will also boost the final cost.
How easy is the product to mix and apply?
Ease of use may also influence overlay selection, especially if you're the installer. Some products come preblended like a cake mix, and all you need to add is water. Others require mixing the polymer additive and any pigmentation desired with the cement and other dry ingredients. Some overlays can go right over properly prepared surfaces; others require application of a primer or bonding agent before overlay placement. Pourable, self-leveling systems tend to cover floors faster with less finish work than trowel- or spray-applied products.
How much maintenance is required?
A decorative overlay should always be coated with a compatible sealer to help protect it from water penetration, stains, dirt, and grease. Sealed surfaces will also be much easier to clean. Floors typically require only routine sweeping to remove any abrasive particles and occasional wet mopping with a mild detergent, depending on how much traffic they receive. Occasional pressure washing may be needed to clean exterior slabs. Some overlay manufacturers recommend resealing surfaces annually, depending on the amount of traffic and exposure to freeze-thaw conditions.
What look do you want to achieve?
Of course, the main reason to use an overlay system is to beautify existing concrete. Determine the color, pattern, and texture you want for your rejuvenated surface, and then find a product that can achieve the distinct look you desire. Consult with the overlay manufacturer and your installer for advice. Ask to see samples of various finishes and color selections as well as a portfolio of completed projects.
TIPS & TECHNIQUES FOR APPLYING CONCRETE OVERLAYS
Each contractor has their favorite application methods. Here are some expert insights: