Polished concrete, a popular, timeless floor
The durability of these floors make them an attractive option for home owners.
In his book, Guide to Polished Concrete Floors, author Bob Harris says that whether you are working with a homeowner or a commercial client, it is imperative that everyone knows what to expect from polishing – both the end product that can be achieved and the process of achieving it.
On residential projects, flooring contractors will typically work directly with the homeowners, who may have difficulty deciding which flooring system best suits their needs. Often, they will focus on certain characteristics they like, such as a high-gloss finish, a specific colour scheme or ease of maintenance, rather than a specific flooring type. Conversely, when working with architects on buildings part large commercial jobs, they know precisely what their needs are. They have extensively researched the different flooring options and have already chosen polished concrete for a variety of reasons. Bob provides this gloss level table for polished concrete flooring projects:
Depending on the diamond grit that is used, different ranges of polish and different levels of sheen, from matte to a wet and glassy mirror-like finish can be achieved. Here is an overview of the different levels:
Level 1 polish
Polished concrete is usually categorised in levels ranging from 1 through 4. A level 1 polish usually can be obtained by stopping at the 100-grit resin bond. When you look directly down at the floor, it will appear somewhat hazy with little if any clarity or reflection. This is a good grit to apply topical sealers.
Level 2 polish
A level 2 polish is obtained by stopping at the 400-grit resin bond, producing a low-sheen finish. When you look directly down at the finished floor and at a distance of roughly 30m, you can start to see a slight overhead reflection, although it is not crystal clear. The grit level produces a low-lustre matte finish.
Level 3 polish
A level 3 polish, achieved by going up to an 800-grit diamond abrasive, will give the surface a much higher sheen than that of a level 2 finish, and you will start to see good light reflectivity. At a distance of 9-15m, the floor will clearly reflect side and overhead lighting. Many big-box commercial stores stop at this finish level because of concerns that a higher degree of polish could produce a slippery surface, especially if the floor becomes wet.
Level 4 polish
This level of polish produces a high degree of shine, so that when standing directly over the surface, you can see your reflection with total clarity. Also, the floor appears to be wet when viewed from different vantage points. A level 4 polish is obtained by going up to a 3000-grit resin-bond diamond or by burnishing the floor with a high-speed burnisher outfitted with specialty buffing pads.
Polished concrete is typically a multistep process requiring the use of machines equipped with diamond-segmented abrasives that grind down concrete surfaces to the desired degree of shine and smoothness. Similar to sanding wood, you gradually progress from a coarser-grit to a finer-grit abrasive until you achieve the desired degree of smoothness and sheen. Grit, in this case, refers to the particle size of the diamond. The higher the number, the finer the grit level.
There are a variety of polished concrete flooring systems on the market. Mike says that the systems are very different from each other and the one that they use depends on the type of application and the thickness of the floor.
“We use Mactool’s solutions and have found that their sealants and additives work very well. There are also systems by TAL and Flowcrete which are very effective,” adds Mike.
There is also a minimum slab requirement for polished concrete flooring of 25 MPA. If this strength can’t be achieved, then an additional 50mm, 60mm or 80mm screed must be poured.
“Nothing less than a 25 MPA screed should be used. If the concrete is softer, then liquid hardeners need to be used to harden the surface,” says Richard.
The cost associated with concrete is a multifaceted discussion. The upfront cost to create an appealing floor is often higher than most floorcoverings, 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.
We asked Geoff McLea and Henk Viljoen from Mactool to provide some insights on the cost of polished concrete floors when compared to other types of floors.
“If you have existing concrete, you can look at anything from R300 to R800 per m² for exposed aggregate. This will depend on the size of the floor and condition. Obviously, a 70m² floor will cost more than a 1000m² floor,” says Geoff.
“There’s a number of different decorative overlay types on the market that can be polished. You get cement-based products and epoxy-based products and there are various types ranging from R500 per m² to R2 500 per m². It is best to discuss the various systems with your contractor or architect,” adds Henk.
Brian says that South African companies are notoriously bad with floor maintenance, which can be attributed to lack of regulation.
“In Europe, a specified maintenance programme is included in a flooring system and facilities managers stick to the programme. In South Africa, maintenance happens on an ad hoc basis. The maintenance contract can be quite complex, depending on whether the floor is installed in a high- or low-traffic area and the type of traffic the floor will receive. Maintenance should be done with a burnisher or polishing machine that has diamond-impregnated pads, which can transform the floor back to its original sheen,” says Brian.
Geoff and Henk recommend standard monthly maintenance using a neutral cleaner and cleaning pads. “Do not use any acidic or alkaline based cleaners as these will affect the polish. Foot traffic will also influence how often maintenance needs to be done,” they say.
Mike adds that if a solvent based polishable sealer is used, it will need to be recoated every 3-4 years. “More expensive sealers such as a lithium sealer that penetrates the surface will ensure a less frequent maintenance schedule. Every four years, you just need to apply a bit of sealer and buff it up again, making it a very low-maintenance system,” says Mike.
Geoff and Henk point out that the acoustics of a space with a polished concrete floor is similar to other hard surface types. Richard adds that in very small, confined areas, there may be a slight echo if the floor is concrete and there are also concrete brick walls.
“Our office in Jet Park has an HTC Superfloor and we found that by simply adding normal furniture to the space, a lot of the echo was absorbed,” says Richard.
“Many people ask whether a polished concrete floor leads to a noisy space. I would say that the acoustic impact is the same as a ceramic tile floor,” adds Mike.
With polished concrete flooring being one of the hardest, most durable floors on the market, clients can rest assured that their flooring products won’t end up on the landfill.
“If the floor is installed properly, it will last a lifetime. The excellent longevity of the floor makes it a truly sustainable product,” says Brian.
“Polished concrete isn’t something that will go out of fashion. Even if it does, you can lay another floor on top of it, so there is no waste,” says Mike.
“It’s easy to clean, light reflective and it will last for life as there is no wear and tear,” says Richard.