Concrete Resurfacing Guide – A (Not So) Quick Introduction
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“The Crime Scene”
It was a dark and stormy night. Ok, not exactly, more like 3 p.m. in the afternoon on a Sunday just before the Cowboys were going to play. Things looked good, the ‘Boys’ were favorites. My wife had gotten some snacks together, and we were stretched out on the favorite couch – the one that has over time comfortably “molded” itself to my posterior. We were laid out, munching away while watching the usual pregame jibber-jabber with our two dogs (dachshunds) staring intently at us to see if anything would fall on the floor; let’s just say we never have to worry about “Cleanup, aisle 4!” with these guys around.
We were running low on the soda, so my wife jumped up and headed to the kitchen with the two little ones in tow, knowing they have a better chance of scoring in there. I shifted around a little, settling down deeper into the couch. The pack had only been gone for a couple of minutes and I wanted to be completely relaxed before they got back when this high pitched scream rolled in through the door. It raised the hairs on the back of my neck, “Did she fall? Did she cut herself?” I catapulted out of the sofa and sprinted towards the kitchen fearing the worst, but I didn’t get that far. There in the middle of the dining room stood my wife, scowling at me, yelling at the top of her voice, and jabbing her finger downwards towards the floor. That’s where I saw it, the final straw.
The crime scene
Sitting there was what every homeowner who ever has mixed dogs and carpets fears most: a small pool of puppy piddle. I quickly looked around, trying to spot the culprits but they had beaten a hasty retreat. My wife was beside herself. She had turned her back for just a few seconds when one of them had unashamedly taken the opportunity to relieve themselves. And do it after they had been outside all day! It really was the last straw. For months we had been noticing how the dining room was developing a “musk”, to use the word mildly. Between #1’s, which are hard to spot and #2’s, which are obvious, we were starting to feel embarrassed to have guests over. It was time to take action. Of course, the first thing anyone would reasonably think would be to “We’ll just potty train them and that should take care of the problem.”
Not us! We decided it was time to get rid of that carpet and just do some concrete resurfacing (in this case a microfinish overlay) and if they need to go, no more stains or smells! My wife, who had been pushing hard on that same theme for the last couple of years loved the idea. The frown turned upside down and we finally able to settle down to watch the game. The two little ones? Their punishment was being banished to the yard for the duration of the game and no treats afterwards. They got off light.
“Rehab” – Concrete resurfacing to the rescue!
Three weeks later, we were ready to get down to business. We decided to go with concrete resurfacing in all the carpeted areas which included the dining room, entryway, and the living room, about 600 square feet total. Carpet tear out was the first step. Here you can see Armando, one of the installers, first cutting the carpet into wide, more manageable strips that we then rolled up. In my case, the carpet underpad (that foam like surface under the carpet) wasn’t glued to the floor so it made removal much simpler. Can you see what shape the floor is in? Yep, all those white spots are paint that was just splattered everywhere. Nobody cares what happens to the floor when they’re building the house. They figure you’re going to cover it up anyway so we find paint, varnish, pipe dope, glue, permanent marker, just about anything that can be spilled, splashed, dropped, sprayed, or dripped on the floor. This is why we often have to do concrete resurfacing on remodels instead of a direct acid stain. This project was no exception.
With a direct acid stain we’ll pull up the carpet, tile, linoleum, or laminate, clean the floor as best we can (and I never guarantee that we will get everything up), stain the floor, then seal and wax it. However, it’s kind of a WYSIWYG (those older computer geeks remember this term – What You See Is What You Get). Any imperfections left on the floor will still be visible after a direct acid stain because it’s a translucent process. Imperfections includes carpet glue, tile ghost image (a pattern that remains visible on the concrete floor even after removing the tile and cleaning the surface), tack strip holes created when we pull up the tack strips that held the carpet down, and just about anything else that was too tenacious to be removed by the cleaning process. Keep in mind that we can’t be too aggressive in cleaning. If we sand or grind parts of the floor, they will look different from the rest and tend to stand out, so it’s kind of a delicate balance between cleaning it and damaging it. (Most of our direct acid projects are exterior areas like patios, driveways, sidewalks or interiors of homes that are new construction when nothing else had been installed.)
The builders figure you’re going to cover it up anyway so we find paint, varnish, pipe dope, glue, permanent marker, just about anything that can be spilled, splashed, dropped, sprayed, or dripped on the floor. This is why we often have to do microfinish overlays on remodels instead of a direct acid stain. This project was no exception. What’s the difference?
Below is a picture from a project we did a few years back that shows what happens when you do a direct acid stain over a floor that previously had tile and carpet. This homeowner didn’t want to go with concrete resurfacing. They were OK with the tile “ghost images” and tack strip holes being visible; and visible they are! So just what creates these “ghost images” and holes? The tile pattern is a result of minerals being brought up through the concrete over time. Many people don’t realize that concrete foundations “breathe”, that is, they’re porous and moisture constantly moves through them from the surrounding ground. It’s not a lot of water, usually just a vapor, but as this vapor comes into the home and hits the ceramic tile it can’t pass through because ceramic is highly impermeable. So it does what water always likes to do: find the path of least resistance. In this case, the grout joints around each tile. Over the years this moisture seeps into the home through these grout lines, not damaging anything but slowly pulling minerals and depositing them right where the grout lines are. And Voila! When you remove the tile, the “ghost image” remains and it can be tenacious. Many times, even after grinding the floor we can still see this pattern, especially in homes where the tile had been on the floor for a long time.
The tack strips are another story. These are actually wood strips with nails sticking out of both sides. The nails facing down are thicker and get hammered into the concrete to hold them in place. The nails facing up are smaller but very sharp and actually jab into the carpet from below and hold it in place. The concrete nails don’t come out without a fight, usually pulling up a small chunk of concrete and leaving divots behind in the floor that still show up after staining. Concrete resurfacing (microfinish overlay) eliminates both the ghost images and tack strips holes as it covers them both up under a new layer of concrete.
Back at my house, after rolling up and disposing of the carpet we went to work on the tile and the tack strips that ran around the perimeter of the room. We like to move quickly with these, so we use an electric demolition hammer to remove them. It really speeds things up compared to a hammer and chisel, especially when you have to blow out the thinset that held the tile in place. Before putting down the concrete resurfacing material we’ll patch deep tack strip holes (1/2″ or deeper) to make sure the overlay will create a uniform surface.
Divot left behind after tack strip removal
Patching large tack strip holes
The most important step in applying concrete resurfacing is surface preparation. We always grind interior surfaces to roughen it up. This gives the resurfacer something to “bite” into. Sometimes we may also use an acidic etching solution to open up the pores in floor depending on the circumstances. Whatever is done, we always prep the surface before applying the concrete resurfacer. When we grind, we use a shrouded grinder that is hooked up to a vacuum system. This almost completely eliminates any dust created by the grinding process and removes paint, drywall mud, and anything else we usually find on the floor.
Time to apply the concrete resurfacing material (microfinish overlay)! So just what is this overlay material anyway? It basically a combination of cement, sand, and a special polymer (fancy word for glue) that allow it to stick to the floor in a thin coating. If you just mixed up a batch of cement, sand, and water and put it down in a thin coat it would peel right up in a few days. The polymer is the key. It’s incredibly sticky and its adhesive strength increases with time. There are different manufacturers for concrete resurfacing materials. We normally use an Elitecrete product called Thinfinish for our first coat and then follow up with a second coat of another Elitecrete product called Microfinish. The Thinfinish leaves the floor with a somewhat sandy texture, excellent for abrasion resistance but it would be a bear to mop or sweep it. The Microfinish, having a smoother consistency, flows between the larger sand grains of the Thinfinish coat, filling them in and creating a smooth floor. Combining both products for use on interior floors provide strength, beauty and low maintenance. We pour the bag mix into a few quarts of water, add some pigment to it (in this case a beige), stir it up and then squeegee it on the floor. We spray a light coat of water on the bare concrete before applying the overlay, which helps keep the mix wet. The concrete is so dry that if we didn’t do this, the mix would get drier and drier as you moved it over the surface, eventually reaching the consistency of chewing gum. We also try to lay it down as smoothly as possible that way we don’t have to sand it as much later.
After applying the 1st coat we need to wait for it to dry before the next step. This really depends on the environment. If it’s cold outside, it can take six or seven hours for it to completely dry. Normally though, it’s two to four hours. Once it’s completely dry we can apply the second coat. If the floor was in really bad shape (a lot of divots and other issues) we may apply a third coat of concrete resurfacer to cover these problems up.
However, most floors only require a couple of coats of the concrete resurfacing material, so the second is usually the final one. Whether 2nd or 3rd, this last coat is always microfinish and because we want it to fill in the sand grains of the thinfinish coat we switch to a steel trowel to “force” it into the pores. This is where we get “up close and personal” with the floor and this is where it gets a lot of its final “personality”. The troweling process creates variations throughout the floor. Some places get troweled a little more than others and this “burns” the surface, making it denser and causing it to take stain differently. As you can see in the picture, we use larger trowels for big areas and smaller ones for detail work. It’s a lot of work while moving on your hands and knees and even during the winter you will definitely break a sweat. No matter how careful we are, we will never get a perfectly smooth surface, even after passing over it several times with the trowel. So, after this final coat has dried for a few hours we pass over the entire surface of the floor with a floor scraper. This shaves off any high points and further smoothes out the floor. It also burnishes some of the higher spots on the floor giving it a more marbleized look. This step doesn’t take a lot of time but it’s an important part of the process. I like to walk across the floor barefoot as that way I can feel if I missed anything.
My wife insisted that I score the floor. By scoring we mean cutting a pattern through the concrete resurfacer and into the actual concrete floor. In this case it was 36″ wide diamonds cut using a special circular saw with a diamond blade. She decided we would do the raised dining room area and the sunken living room. The saw used in scoring can generate a tremendous amount of dust, so we connect it to a vacuum cleaner that pulls most of the dust away from the cut. To prepare for scoring we first need to “pop out” the pattern on the floor. We measure out the pattern then use a chalk line to make the lines we follow to score the floor. That way if something doesn’t look right or we change our mind we can easily erase the chalk line without damaging the floor. She liked what she saw so we proceeded with the scoring. The diamond blade on the saw is normally 1/4″ wide. We cut a shallow groove in the concrete floor doing what we like to call a “decorative cut” which isn’t too deep or it would be a cleaning problem. We always cut completely through the concrete resurfacing material and into the concrete floor; that way we have a consistent looking score line and as we expose some of the sand, cement, and stone that make up the floor in the cut it gives it a more interesting look.
After passing over the entire pattern with the circular saw we have to do touchups with a smaller, handheld grinder. No concrete surface is perfectly flat over its entire span, there are always dips, normally small ones, but as we are doing a shallow cut, the blade from the circular saw may not cut into it. The handheld grinder finishes it off.
After scoring we have one more step to do before the staining process. We need to protect all the walls from the overspray. We do this with a pre-taped plastic drop cloth. As you can see in previous pictures we put down blue painters tape along the entire length of the trim running around the room. We apply the taped edge of the drop cloth to this and then pull it up to cover about 20″ of the height of the wall.
At long last we get down to staining. Here, we had two choices: acid or dye staining. Lately we’ve been doing much more dye staining than acid staining on concrete resurfacing finishes (microfinish overlays) for a couple of reasons. First, it’s easier to control. Acid staining is reactive while dye staining is pigment based. Reactive staining is much harder to control. The stain will create a lot of variegation but we don’t have much control on how dark it gets. With dye staining, we consistently get the same result because we just mix the pigments to the proportions we need. Second, speed. Acid staining, takes time to do its thing and it requires additional neutralization step that stops the color from continuing to darken. Dye staining just requires for it to dry and we are ready to start sealing. Lastly, dye staining gives us a much wider palette of available colors than acid staining which has about eight primary colors.
For this project I went with the dye stain. We mixed up a batch and then sprayed it down starting with the borders which we wanted to make darker than the rest of the floor. It normally takes two coats to get the right color combination. It went very fast and by the time we finished spraying the last of the floor, the first part was already dry and ready for the second coat. We wrapped up the project pretty quickly from this point. Two coats of sealer followed by two coats of wax and it was done! With a sigh of relief I took a step back and liked what I saw even though I knew the opinion that really mattered was my wife’s. She walked in the door and just loved it! Calls were made, friends and family brought over, and much preening was done. I was just glad it was over. The next day, after patting myself on the back, I introduced the new floor to the dogs. They loved it too! So much so that about five minutes later I found my first “accident”. But you know what? That’s what’s great about concrete resurfacing for floors, you see things right away. You easily wipe them up with a towel, and no stains or smells!
Here is a video from our youtube channel that shows the entire concrete resurfacing process from start to finish.
Thank you for your time to read this concrete resurfacing primer. We hope it helps in explaining how we apply concrete resurfacing on interior projects. I’m not going to say it’s the only way to do this type of work; it’s just how we usually do it. If after reading this you would like us to resurface and acid or dye stain your floors just contact us through the link below.