Our friends at Stained by Design have sent along some more great information on concrete. We've have several quality posts on acid stained concrete and this one covers information on decorative concrete overlays.Overlays are a way to cover up a current interior or exterior concrete application. If you are a Do-It-Yourselfer, here are some application guidelines. If you prefer to have a concrete company do the work, use this info as a guide to make sure they're doing it right. Joe's the expert in our book and anything he says goes:
"Decorative Concrete, or Architectural Concrete, as it is also called, is a way to put a new face on existing concrete. The existing concrete may be pitted, aggregate-exposed or have a mix of both a smooth and rough finish. Several new thin layers of a specially modified concrete mixture are applied to the existing concrete to create a new surface. As the name implies, the finishes are decorative enhancements that add to the architectural beauty of existing concrete, but they are not structural in nature.
Concrete Overlays fall into different categories but share steps in the evolution of the final product. The installation time runs from 3 - 7 days depending on the size of the area, the selected style and complexity of the pattern. There are many manufactures of overlay systems. Some require primers, some call the steps or mix a different name. This is intended to be generic in nature, but I have to call the steps/mix by the name that I use.
The typical steps are as follows:
1. Preparation. This step is common to all applications.
a. The surface is pressure washed or cleaned with a floor prep machine depending on if Exterior or Interior.
b. A mild Acid bath is done and then neutralized. This opens the pores of the concrete and prepares it to bond with the next application. (An Acid Bath is NOT done for staining a Concrete Slab). For those interested in staining concrete slabs, please see the archives sections for previous posts about acid stained concrete.
The following steps only apply to concrete overlays.
2. A Skim Coat (also called a Base, Bond or Scratch coat.) This step is common to all overlay applications:
a. Cracks in the surface are treated if needed.
b. A Skim or Scratch/Base coat is applied to the surface and allowed to dry.
*** The steps below are by style. Depending on the complexity of your desired surface, modifications may be made.
3. Texture Applications: There are several styles that fit this category (a Knock-Down finish is in this category.)
a. Basic Spray Texture would have an additional Base Coat added before the Top Coat is Sprayed on. I feel the additional base coat is needed to give strength to the final product. After the second Base Coat, the Top Coat is sprayed over a Stencil, Tape or a Seamless pattern.
b. Flagstone coatings also receive two Base Coats for the same reason above. The next step is to apply a 1/2" Nylon Tape to the surface to mark off the "rocks/stones."
c. The Flagstone pattern is then coated with the Top Coat and after a dry time, misted with additional colors.
d. The tape is then pulled off to reveal the pattern and the surface is then sealed.
4. Faux Slate/Tile Applications:
a. The Top Coat material is mixed and applied with a pool trowel to achieve a look that resembles a light Slate Texture or a swirl-type texture found on some tiles.
b. After drying overnight, the desired pattern is marked and scored.
c. Stain is applied to the surface in several coats to achieve the desired color, tint and tone.
d. After an overnight dry, the surface is sealed.
e. NOTE: This texture may also be referred to as a "Knock-Down" when it is done to resemble Cool Deck.
f. There are other variations of this style that can create a personalized tile unique to your home.
5. Micro-Finish Overlay:a. The most common use of Micro-Finish is to overlay a slab that would not react well to acid stain. The final result is a surface that actually achieves a higher degree of mottling and tone than concrete.
b. A Micro-Finish job will get a second Base Coat.
c. Two applications of Micro-Finish are applied with a pool trowel. This process fills in the small voids in the surface and results in a smooth even surface.
d. The floor is machine-sanded to further smooth the surface and remove any trowel marks.
e. The pattern is scored and the surface is stained in the desired color. After the stain works for about 4 hours, it is neutralized and rinsed.
f. Once the surface is dry it is sealed.
6. Thin-Stamped Overlay:
a. Texture Pave is the ultimate top-coat that is applied to the surface and accepts the stamp pattern.
b. A "Wet Bond" coat is put down in advance of the Texture Pave.
c. The Texture Pave is spread out with a Gauge Rake to ensure a consistent application.
d. After the surface has set up enough, it is stamped with the Texture Skin.
e. The Texture Skin makes the Slate pattern in the surface.
f. After the Stamp, the material will dry over night.
g. The pattern is then scored and stained in the desired color.
h. Once the surface is dry it is sealed.
7. Sealer Options:
There are several sealers available and the choice of sealer should be determined by environment and use. Some of the overlay styles/staining required longer dry times than others. Most surfaces can be sealed the day after staining.a. CSS. This is the Primary sealer for Exterior applications. CSS is a 53% solids, UV inhibiting sealer. It penetrates the surface and prevents mold and mildew from getting a foot-hold on the surface.
b. AUS-G: This is a Aliphatic Urethane sealer. It is UV stable and offers higher abrasion resistance. It requires a longer cure time.
c. Clear Epoxy: This is the best sealer for Industrial use. It cures up to over 14,000 PSI and is odorless. However, it requires the longest cure time and does scratch easily. It is often selected to support forklift traffic. I can be used in a residential application, but should be top coated with AUS-G for better wear.
d. Colored Epoxy: Colored Epoxy comes in 10 colors and is the best coating for areas such as loading docks where high wear and heavy weight is the primary concern.
e. Wax: All interior applications should receive coats of a commercial quality liquid wax. This wax is applied with a looped-end Rayon mop. The purpose of the wax is to provide a sacrificial coat to absorb the scuff marks and prolong the sealers life. An analogy for wax is to think about a car. The car color (the stain on the concrete) is covered with Clear Coat (the sealer) and car wax protects the clear coat. So long as you keep up with the wax, you won't have to have your car painted or your floor resealed."
To find out more about Architectural and Decorative Concrete Overlays, visit Joe's site. You can also call Joe if you're near Louisiana at (337) 316 - 4505. If you need to find a decorative concrete specialist in your area, you can post your project for free with ConstructionDeal.com.
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