Concrete Floor Resurfacing Options

Concrete Over The Years

Concrete and concrete floors have been a part of our society for a long time. Concrete is timeless in a sense and can be hip or trendy when designed into the overall theme of a property. The benefits of choosing a “concrete look” that come to mind are durability and minimal maintenance. Concrete floors, often considered cold, can be warmed up with area rugs and or other soft accents.   

About 25 years ago a move to a bohemian look took place in design and concrete floors started becoming popular in downtown lofts as older buildings were vacated and younger generations were moving in. These loft apartments and offices were becoming occupied for their industrial look and for the overall utility as well as their proximity to the city. From San Francisco to New York, our industry began getting the call to help building owners and tenants transform their concrete into finished floors.  

At that time, the techniques varied a lot but included floor scrubbing with a floor machine or swing machine such as used by the janitorial community as well as a few of us concrete restoration nerds. The machine properly outfitted with a stiff brush could scrub and clean the existing concrete in a way that left the original smooth hard trowel or steel trowel finish in tack. This smooth hard trowel finish was and still is a remarkably effective finish and, in many cases, is hard to beat and should be left alone.   

Concrete Options  

We have a hard trowel or steel trowel concrete finish; this has an awesome aesthetic when it is done right during the original pour. It may only be replicated by completely re-pouring the concrete or, in some cases, with a cap of new concrete and or a concrete topping.  I say this with a deference to my concrete restoration community, you cannot beat the original pour, the original mix, design, and top-notch concrete professionals placing and finishing the concrete. The methods for applying and protecting original pours continue to improve as well as the equipment and the mix designs. There is nothing like doing it right the first time.      

The reason that there is a large and growing industry for resurfacing concrete is that most concrete was not placed and finished in an optimal way therefore the market demands have offered options for bringing the concrete back to life.  All too often well-intentioned contractors end up grinding or damaging an existing, hard trowel surface rather than working with the existing surface. There are attributes of grinding and processing the surface where concrete has become damaged or stained in ways that are not acceptable to achieve a particular look and function; for example, this is the best option when a new color, higher gloss, smoothing and leveling, patching or higher chemical resistance finish is desired. The old hard trowel is sometimes too dark, but by a grind and seal or polishing application, it can be lightened up. We have many choices today as the number of processes to help restore or improve the original concrete finish have come along.   

When you or your client desire a nice durable concrete floor and the current floor is not in good enough shape to simply clean, buff or wax, what can be done?  

For many, what has become popular is concrete polishing and or concrete grinding and sealing. What is the difference? Which one is best? Do they look different? Do they require different maintenance programs? How do they differ from simply leaving the original hard trowel concrete? Most probably do not know the difference and why would they? It likely won’t matter until you specify or order the wrong process and you don’t achieve your goal of a long-lasting, cost effective, aesthetically pleasing concrete floor but instead get something that is too expensive and ruins a project or costs the building owner unneeded heartache.   

Concrete Polishing   

I will start with the most popular and well-known method for rejuvenating concrete and what most in the industry refer to as concrete “polishing.” Concrete polishing is at a point where it is mainstream and utilized on large grocery store and box store chains including HEB in Texas, Whole Foods, Costco, Home Depot, Lowes along with popular food and beverage establishments like Starbucks and Chipotle. Concrete polishing is beautiful, especially if you have a good concrete slab to begin with.   

The polishing will only be good as the concrete, but with that said, there are some fantastic products and equipment to remake an old, tired concrete floor into an attractive surface. The process involves an assessment of the surface and a plan. Part of this plan should include a mock-up so that all (property owner, tenant, contractor, architect, and installer) are aware of how well a slab will “polish.” Once the plan is in place and a mock-up is complete, the work begins.  

To begin, large grinding and polishing machines that use coarse diamond pucks grind and remove what some call “the skin” of the concrete. This process is like what is done to prepare concrete for coatings or sealers.  During this process, you can opt to cut down and expose the rock or aggregate - setting the tone for the entire look. This cutting process reveals the rock that can lead to an entirely distinctive look than you had before the cut. Done right… this can look like Terrazzo!  Once the original cut is made, the diamond pucks are changed out from super coarse, to coarse, to medium, to finer and finer and finer grades which lead to an exceptionally smooth, brighter, and shinier surface.   

In the process, concrete hardeners are sprayed on along with elected color if desired. The final passes include what some call a “sealer” or a “guard” which is a superficial protectant and enhancing treatment that will give the floor a bit more shine and bring out some of the “color.”    

Grind and Seal  

Another similar process (and a little less well known) is concrete grinding and sealing.  A grind and seal application consists of the concrete being ground in a similar nature with similar machines to the concrete polishing process but rather than coming back over the surface with finer and finer diamonds, the surface is sealed with a sealer that will act as the finish right after the initial cut and hone. Where this can be confusing is when we consider what are applicable sealers for this application.

Suffice it to say, there are dozens of types of concrete sealers but for sake of distinction, we typically look at them in a few groups:  

• Sealers that soak in and do not create much of a build, which could include the “guard” sealer - an option of the concrete polishing method outlined in the previous paragraph.   
• The penetrating sealers that do not offer much protection, but also do not usually lead to much problem so they are sort of a safe bet…but you do not get a lot of protection. These penetrating or impregnating sealers can be anything from silanes, silicates, and siloxane sealers to lighter-bodied and low solids acrylic sealers. These sealers are also used on block walls or larger concrete pours for dust proofing or water repellency. The acrylic sealer, a member of this penetrating sealer family, is the most popular for outdoor decorative concrete as they are easy to apply and lower in cost. 
• Heavier duty, high-quality sealers include epoxies and polyurethanes (some solvent based and some water-based) that are applied thin but have a decent amount of build and durability to give chemical resistance and protection from staining. These sealers, or coatings, were derived from the industrial flooring industry as well as the industrial coating industry. Two-part polyurethanes are what we typically see applied to steel bridges, industrial machinery such as tractors, aircraft, and military ships.  

There are clear distinctions in the chemistries of the sealers, how heavily they can be applied and their potential depth of penetration.   

The industry has evolved and more often a grind-and-seal application is preferred, especially where chemical resistance is a concern, for example, in bathrooms, restaurants and or grocery stores where food or other contaminates will be spilled. This also goes for parking areas where cars could leak oil or in schools where an art or shop class might spill materials on the floor.   

So, what is the difference?   

Grind and Seal usually can be done faster, saving labor but requiring various amounts of time for sealers to cure properly before access is permitted. Challenges to grinding and sealing can be improper sealer selection or application. Sealing off a floor can also be a problem when there is moisture present in the concrete substrate; when moisture rises due to the temperature or humidity changes, whitening and or dislodging of the sealer can occur. This has been overcome in some cases by applying a high-quality sealer very, very thin to allow vapor to pass through. Some water-based technologies allow the vapor to pass very well, that said they still need to go on thin.     

Polishing is much more popular as there are many more contractors offering this service and surface, but a full polish usually cost a little more.  Grind and seal will bring out the color of the floor and darken it to various degrees. Polishing can have a bit more of a natural look but there are grind and seal options for natural looking sealers as well. Some concrete does not polish well and is better suited for a high build sealer or coating.  

Maintenance is necessary  

Long term maintenance should be considered before selecting your concrete floor treatment. Also consider who is going to do the maintenance and the type of contaminants that will be regularly encountered.   

When you select one of these floors you need to understand the required daily or weekly maintenance such as how to address spills (wine, food, mustard, urine, beer, etc.). Concrete polishing is touted as exceptionally minimal maintenance and it is. It is tough and scratch resistant (especially if shoes or feet are clean and you are not dragging abrasives such as sand onto the floor). But there is maintenance and it usually requires concrete polishing and maintenance professionals to work together on such a program.   

There are benefits to a polished concrete surface but remember that the finished surface is porous and can be stained much easier than a sealed surface. Grind and sealed concrete floors are a little more straight forward for maintenance in that if a proven, high-performance epoxy or high-performance polyurethane sealer is selected and installed properly , the surface can be maintained in the same way almost any “no wax” floor can be maintained with the option of waxing if needed.   

Waxing is still popular and works well on residential and some retail floors where removal of the scratches in the surface is desired.  A polished concrete floor usually requires re-buffing, burnishing and or reapplication of the guard/sealer. So, both systems require maintenance but the daily and the longer-term maintenance is different. These floors thrive when kept clean with typical cleaning methods such as sweeping, dust mopping or microfiber mopping.   

What process is best?  

What do you choose? If it were me, I would specify either system where best suited. Areas that 1) do not have spillage, 2) do not pose concerns of moisture vapor from the substrate, and 3) where I can commit to a solid upkeep program would cause me to lean towards a concrete polishing system. If the desired finish is a higher gloss, protective coating for spills with a simpler maintenance program then I would go with a Grind and Seal installation. To help choose the perfect system and confirm the desired finish can be accomplished with this concrete area, I would recommend a full-scale onsite mockup for approval including pricing, warranty (if any) and a clear maintenance schedule.