Severe weather can be a problem here in Texas, as one homeowner in Denton discovered after an intense hailstorm. The hail slammed into his concrete patio and caused it to chip up in several places. He called us about repairing the ruined concrete and laying down a stamped concrete overlay, so we drove over and got to work.
A crucial step of any stamped concrete overlay project or other concrete resurfacing project is surface preparation. The existing concrete surface needs to be clean of dirt and stains and clear of any coating, sealers, or flooring materials. Our Denton homeowner's patio had a concrete coating that had been chipped off thanks to the hailstorm; and it had to be removed before we could begin work on the stamped concrete overlay. Leaving the old coating on wasn't an option; it had been weakened from the hammering it had taken and though our stamped concrete overlay would stick to it just fine, there was no guarantee that the original layer wouldn't peel off in the future, taking our new material with it.
If the existing concrete is new, all it may need is a power wash or buffering to remove any dirt before the overlay can be poured over it. Which method we use depends on if the concrete is indoors or outdoors. For concrete that is indoors, we first soak the surface with concrete degreaser, and then we pass a concrete buffer over the area. We finish by removing the degreaser with a shop vac. For concrete that is outdoors, we can typically skip the concrete degreaser and use a pressure washer to clean the concrete surface.
Since the patio in Denton already had a coating on it that was partially peeling off, we had to do a bit more work to prepare the surface for the stamped concrete overlay. We used a combination of chipper hammers, scrapers, and grinders. These tools can remove various stains, coatings, and sealers as well as any flooring materials that may lie atop the concrete. Chipper hammers are good for removing flooring materials like wood, tile, and in this case, a coating that is failing. With wood, we place a sharpened chisel into our chipper hammer and literally "shave" the wood right off the floor, it's a very labor intensive process as we have to go over every square inch of the floor. If the concrete surface is covered in ceramic tile, we normally find thinset (a layer of concrete "glue") that is used to adhere the tile to the concrete floor. It is usually about 1/4 of an inch thick. Chipper hammers will break up the ceramic tile and the thinset underneath, at which point our grinders can then take care of whatever's left. Scrapers, meanwhile, are extremely sharp steel razor blades mounted on a push rod that can be used to scrape off coatings, sealers, and flooring materials. Normally we use these to get VCT (vinyl composite tiles) and linoleum up of the floor. Grinders can be used to remove dirt, stains, paint, adhesives, varnish, or epoxy floor coatings, as well as flooring materials. Grinders are pretty useful for a number of situations; they can be used to smooth a surface or make it rough, whichever's required and depending on the grit of the grinding stones we use. They can level uneven surfaces and create a smoother finish than other tools.
For our Denton, TX stamped concrete overlay project we first used chipper hammers, then scrapers, and finally grinders which were used to open up the concrete, making it more porous and easier for the new overlay to stick to it. Now, we don't use all of these tools in every project; it all depends on what's on top of the concrete surface. After removing the coating at the house in Denton, we were able to proceed with the rest of the stamped concrete overlay project to the beautiful conclusion you can see here.