Concrete Flooring Update: Concrete’s appeal hinges on its minimalist style and functionality - Apr 2019
By Jessica Chevalier
The use of concrete as a finished floor is a practice that brings nearly as many challenges as it does solutions. Concrete is hard underfoot; it contributes to poor acoustics; it isn’t cheap; its sustainability profile is problematic; and the final aesthetic outcome, especially on an existing slab, is unpredictable. In spite of these significant headwinds, the material’s use is widespread and, by the account of the designers with whom we spoke, expanding. Why? Concrete’s stripped-down aesthetic is loved by many, and that drives-and will likely continue to drive-the material’s specification, especially when paired with its strong performance and maintenance stories.
Concrete offers a minimalist appeal very much in line with current design aesthetics. “I like the approach of leaving a building as pure and unfinished as possible,” says Stephanie Wexler of Memphis, Tennessee-based Archimania. “Letting the actual building materials be the finish materials offers more character and promotes the use of craft, as opposed to machine-made products, which make all buildings look the same. You have to have a slab. Why not polish it as a finish material? The result is beautiful, and many people mistake it for terrazzo.”
NATURE VS. NURTURE
In an era where nearly anything can be made to look like anything else-both in flooring and culture-concrete holds an almost nostalgic appeal. Using concrete as a finished floor takes something ordinary, even banal, and creates something handsome, an enduringly loved trope. It’s an aesthetic that grabs us, and a story that compels us-the spatial version of a make-under, stripping away the layers of flounce and façade to find the beauty within, but just like a dewy, barefaced model on the magazine cover, concrete didn’t roll out of bed looking like a finished floor, nor is it as natural as it first appears.
How concrete has come to be characterized as a natural product is perhaps the greatest oxymoron of the material. Yes, it is comprised of organic ingredients-stone, rock or sand aggregate; water; and cement, which, according to The Portland Cement Association is made, “through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients. Common materials used to manufacture cement include limestone, shells, and chalk or marl combined with shale, clay, slate, blast furnace slag, silica sand, and iron ore.” However, it certainly isn’t like hardwood, cork or stone-single-ingredient materials simply transformed into flooring, not inherently changed.
In fact, standard concrete has a fairly questionable sustainability profile, requiring a great deal of water and energy in manufacturing and producing a great deal of carbon dioxide (CO2) in the process. According to Seattle’s Bullitt Center, which carries the tag line ‘the greenest commercial building in the world,’ “Production of Portland cement is highly energy intensive, and depending upon where it’s produced, nearly a ton of CO2 is released into the atmosphere for every ton of Portland cement produced. It’s estimated that nearly 7% of global CO2 emissions are the result of Portland cement production. Its large volume and weight embody additional energy from transported materials to the plant and the finished product to the site. And the process of extracting, producing and placing concrete uses large amounts of fresh water.” Today, greener cements are being produced, including ones that sequester carbon, but the offering isn’t yet widespread. (For more on alternative-chemistry concretes, re-read Darius Helm’s August/September 2018 EcoLog.)
The fact is, as a flooring, the central reason concrete is viewed as natural is because, visible or not, it’s always there, a non-negotiable, so people see the sustainable cost as a wash. Putting anything atop it-even the most sustainable floorcovering-is adding to the green cost via manufacturing and transportation at the beginning of life and the transportation and energy associated with reuse, recycling or landfilling at the end of life.
Essentially, then, concrete is viewed as sustainable not exactly for what it is but for what it does not make use of. But that, of course, is something.
THE COST OF COOL
As with sustainability, the cost associated with concrete is a multifaceted discussion. The upfront cost to create an appealing floor is often higher than most floorcoverings, even installed ceramic, especially if the concrete is being polished or embellished in any way. However, it is typically cheaper than terrazzo, another poured floor, with a finished look akin to the highly desired flooring, and that is an advantage that many designers point out.
Of course, there is also the fact that a concrete floor will last the life of the building, and, when an aesthetic change is desired, there is no floorcovering to remove and landfill-the concrete can simply be covered over. According to Cameron Wilson of LS3P, based in Charleston, South Carolina, these factors sometimes lead designers and their clients to move forward with finishing a concrete floor, knowing they have the last-ditch option of covering it if the final look isn’t up to par. This was the plan for one of Wilson’s recent projects, a Bitty & Beau’s Coffee in Wilmington, North Carolina. Working with an existing slab that had adhesives remaining from prior flooring installations, Wilson and Bitty & Beau’s owner Amy Wright decided to move ahead with the polishing with the back-up plan of installing a concrete-look LVT if the final product’s aesthetic didn’t pan out. However, the team was more than pleased with the “mottled” result. Wilson notes that key to success in this domain is properly communicating expectations to the owner. “The owner has to realize it won’t be a clean look,” he says.
Keep in mind that polishing is not the only finishing option available for concrete. “I’m not seeing polished so much today-it’s expensive. More often I hear, ‘We want good concrete with a sealer on it,’” explains HOK’s Anne Whitacre-based in San Francisco, California-who has been specifying concrete for more than 20 years. “Then we negotiate about just what type of sealer they want. Do they want the color leveled? What about patching discolorations? There is a wide range of products you can apply to floors, and the owners need to understand that some of them wear off, though, and need re-doing periodically. I’m also not seeing a wide use of stains, like I used to see. There is more interest in ‘natural’ gray. I saw a lot of concrete floors used in tech offices because they were trying to mimic working in a warehouse and also look down and dirty-inexpensive. I’m sure that the people in the space had no idea that their ‘industrial’ floor cost as much as Italian tile or terrazzo.”
During a concrete floor’s useful life, the cost of upkeep is relatively low. Though some applications may need reapplying from time to time, as Whitacre points out, maintenance largely consists of sweeping and damp mopping, unless problems such as cracking arise.
While a concrete floor will not ugly out as some floorcoverings do, there is potential for staining, and sealers that will combat the negative impacts of, say, a spilled glass of red wine come with some challenges of their own. Whitacre recalls a theater project, in which “the firm I worked with didn’t specify any particular concrete mix, but we did use a sealer that would no longer meet VOC requirements. That particular sealer was ten times the cost of any other product on the market, but it did resist red wine stains, which was absolutely paramount for that particular moneyed, cultured clientele.”
In spite of the fact that concrete has been gaining in popularity for a couple of decades and more flooring contractors have ventured into the concrete finishing business, the designers with whom we spoke have not noted any significant decrease in cost that is propelling the material’s continued use. “It’s less expensive than it was, but you can certainly buy cheap carpet cheaper than you can polish a floor,” says Whitacre.
THE ACOUSTIC BALANCE
The days when concrete floors were limited to tech-inspired corporate spaces and industrial-style hospitality applications are behind us. Today, according to the designers with whom we spoke, concrete is being used across the vertical sectors, including in non-patient areas of healthcare facilities. Wexler has opted for concrete flooring in several veterinary hospitals, and Wilson recently specified the material in a sanctuary. “We just finished a large church, and everything in there is polished concrete-the sanctuary, the music rooms, everything,” he recalls. “I see people spilling stuff on it, and because there is no staining or potential uglying, it really gives people the freedom to feel like they can use the space.”
Key to all concrete installations, however, is the mitigation of acoustics. There are a host of ways that sound can be managed-through the shape and structure of the building itself; through products with the express purpose of managing sound, including dry wall, paneling, and decorative products; via added insulation in the walls and ceiling; and through furnishings and area rugs.
Many acoustic mitigation products are expensive, adding corollary cost to what can already be an expensive floor. Acoustic drywall is quite pricey, for instance, as are some solutions that offer both visual texture and sound absorption. For the Le Creuset North American headquarters, which features a concrete floor, Wilson utilized 2” thick acoustic blocks on the walls. The porous cubes are skim-coated and applied individually like tiles, which means there is added cost in labor. And of his church project, Wilson says, “There is lots of sound absorption in the walls and ceiling, and the sound is phenomenal, almost like an old cathedral. The sound is bright. We had to counteract for speaking to avoid an echo, but we got it there.”
Wexler notes, “For places like the animal hospital, with barking and talking, we use a wall panel system to help dissipate the acoustic issues. There are Tektum panels that look like frosted mini wheats or rubber bands. They have a nice tactile quality, lots of character. We’ve used them on both walls and ceilings.”
Wilson notes that he absolutely will not specify concrete for a space if the owners of the space aren’t committed to doing what they need to do to manage the acoustic challenges. On one of LS3P’s projects, the owners announced late in the game that they couldn’t afford the acoustic mitigation elements in their concrete-floored restaurant space and stripped them out. Three days later the president of the business called and said the sound was unbearable, and the group reintroduced every acoustic element they’d stripped from the plan.
Tambra Thorson of HOK leans on furnishings to help control acoustics. She says, “We typically use area rugs, upholstered furniture pieces, felted wallcoverings or ceiling baffles to add a layer of ‘softness.’” And Wexler points out that even the architecture of the furniture selected for a space can be an asset; high-back chairs, for instance, can abet sound mitigation.
Whitacre helped Starbucks derive its first stained and polished floors. She has worked on dozens of projects on the West Coast that have varied from a full six-step polish to simply a clear sealer put on an original concrete slab. Here, she offers her view of the material’s greatest assets and challenges.
• Concrete can be an attractive floor.
• There are no issues with moisture and adhesives.
• It is a long-wearing surface and needs relatively uncomplicated maintenance.
• It can be relatively stain resistant.
• It’s a good option for a floor that people transit through regularly.
• A concrete floor can be noisy due to reflected sound.
• It can get very uncomfortable to stand on for any length of time.
• It can be physically cold.
• It is not recommended for office or restaurant applications due to acoustics or for locations where people are standing all day as part of their job.
THE RIGHT LOOK
Sampling is one of the greatest challenges that specifiers of concrete face, and compounding the frustration of not being able to access samples is the fact that the lack makes it hard to build accurate expectations with clients. Says Wilson, “It’s always good to over-communicate our expectations, to document them. I like to take the client on field trips into spaces with concrete. It’s important to make sure we have a good, tight spec because if it doesn’t turn out, we may be able to go back and resurface with another concrete.” Wilson notes that he has seen a “failed” slab knocked out and re-poured-but that is a drastic measure and a rare occurrence.
“I will say that overall polished concrete-or ground and polished concrete-can be a harder material to explain or convince your client to use,” says Liz Engel of ANF Architects. “Aesthetically, designers and architects need and use physical material samples to finalize finish selections, and getting your hands on samples of ground polished concrete is a difficult thing to do. We’ve ended up borrowing samples from another local architect. All the factors of concrete-like cement mix and aggregate size/color, etc.-make it most logical to have test slabs poured on a job site, and that doesn’t happen till long after the ‘design’ is complete. It seems that it’s an educated guess and trial-and-error to get what a job is really looking for.”
Wexler believes that key to utilizing concrete as a finished floor is being open to whatever final aesthetic the slab presents. She adds, “If a client really wants to control the color and aggregate, results can be a little difficult to guarantee; you have to have a little faith in the material. We probably went through eight to ten samples for our Conservation Hall project to find the right mix. It’s all about finding the right subcontractor, who will be prepared to make up multiple samples.”
Collaborating with the right subcontractor on a new pour is key. “From a specifier’s standpoint, it’s difficult to get across that polished concrete is an artisan finish and entirely dependent on the skill of the polisher and their experience,” says Whitacre. She often utilizes the Concrete Network’s Levels of Concrete Polishing document as a guide, noting that it’s helpful because “it provides levels of polish and also levels of aggregate exposure. This has made it easier to communicate to both the owner and the finisher what our expectations are. And, obviously, a nice looking floor is dependent on the concrete work. I’ve done topping slabs that had more specific requirements so that we can get a nicer polished slab finish. I’ve worked with a number of architects and owners who seem to think that we can take a 12” structural slab and turn it into something like terrazzo. That is unlikely in the best of circumstances. We always have to have a mock-up of the finish in some back corner somewhere because the results are so operator-dependent. I really don’t think that owners understand just how important craftsmanship is to the floor.”
Wexler agrees that utilizing the right sub is paramount. “The first place we used concrete was at an Infinity car dealership in the service area, where ceramic tile is most often used,” she says. “Grout has come a long way, but it still has to be cleaned a bit, especially in an area like this. When you have polished concrete in those areas, it requires significantly less maintenance. But you really need to find a subcontractor who has done it before and has had good success. If you get cracking, it can be really problematic, especially in a service drive area application.” Wexler notes that Archimania completed its first concrete project in 2006 and hasn’t had any problems with cracking, a testament to the quality of the contractors it works with.
Wilson says, “If you want a certain quality level, you have to pay for it. In an existing environment, we will experiment in an out-of-the-way location. Sometimes, depending what was on the floor, you can see patterns. Here in Charleston, people enjoy that. We see it as part of the historic fabric of the city. To us, it represents history and how people have used the space over time.” He adds that sometimes it turns out better than expected, and sometimes worse.
Whitacre adds, “Earlier in my career, it was pretty common for us to incorporate various stains and then finish off with colored wax. The design intent was that we attempt to achieve a 400-year-old Italian villa that had been used for making wine or some such thing. As such, we used two or three stain colors, applied in sort of a mottled ‘artistic’ way, and then used a colored wax to intensify the color. At that same time, I worked on a restaurant concept that used carbon black as an additive, and they had five coats of black wax applied to the floor-the last coat applied three days before the restaurant opening. I think they could have installed black marble cheaper. Those were pretty floors, but way more complicated than they appeared.”
Whitacre learned through the experience of working at a standing desk atop concrete that the material can be very hard on the feet. She says, “I wish someone could come up with a ‘concrete topping slab’ that is a little more resilient so that it’s more comfortable and would absorb sound. Maybe a concrete/rubber mix?”
Slip and fall risk, a concern with concrete, can be mitigated to some extent via toppings, reports Wilson. “Slip and fall risk depends on how you finish,” he says. “There are sealers that are more slip resistant, achieving higher coefficients of friction to meet codes required for public spaces.”
Copyright 2019 Floor Focus