Concrete flooring works well in bathrooms for the same reasons that ceramic tile is so ideal for the same space—it's easy to clean and it can't be damaged by water. Not surprisingly, the same drawbacks associated with ceramic tile also apply to concrete. Concrete can be cold, and it can be slippery if it has the wrong type of finish or surface treatment. Concrete is also very hard, but this is a less significant drawback in the bathroom than it is in other living spaces.
The Structure of Concrete Flooring
Concrete bathroom floors are most commonly found in homes with slab foundations or in basements, where the floor already consists of a 4- to 8-inch concrete slab that rests directly on the soil. Where a high-quality finished flooring surface is required, the concrete slab may be stained, polished, painted, or top-coated to make for a unique and attractive floor. A variety of dying or acid-etching techniques can be used to give a concrete floor a unique look that is like no other material.
If the existing slab is in poor condition, a thin concrete overlay can sometimes be poured over the slab to create the perfectly smooth surface necessary for grinding and polishing. This overlay can be paper-thin, or an inch or two thick, depending on the needs. Overlays are not possible, though, if the slab is in very poor condition or actively heaving.
If concrete is being considered for an above-grade floor, then its heavy weight creates some unique considerations, since standard joist platforms may not be strong enough to support the live-load of a concrete slab. The installation is so complicated that concrete floors are rare in above-grade situations, except in apartment buildings or other steel structures. In the rare event that a concrete floor is installed in a standard wood-framed home, it generally involves framing the floor platform with extra-strong joists and beams, installing some sort of cement-board underlayment, then pouring a thin slab of concrete reinforced with a mesh of rebar.
Advantages of Concrete Floors for Bathrooms
With concrete's reputation as a stark, industrial-looking material no longer an issue, thanks to modern design trends, its advantages as a flooring material for bathrooms have become clear.
Impervious to Water Damage
No amount of water can actually damage a concrete floor. This means you never have to worry about wet feet, damp towels, shower spray, or spills from the sink or tub. While the material itself is immune to damage from water, if concrete flooring develops cracks, it can allow water to pass through to whatever material is underneath. This can be a problem if the floor is laid over a cement board and plywood underlayment, since water can seep through and cause moisture damage. Thus, it's important that you regularly examine a concrete floor for cracks and patch them when they develop.
While professional concrete installers typically guarantee their work for 20 years or so, with proper care, a concrete floor can last for the lifetime of the home. Given this longevity, concrete is one of the more cost-effective flooring materials you can install. Other premium floorings are typically replaced every 10 to 20 years, while you may never need to replace a concrete floor
A basic polished concrete floor costs $2 to $6 per square foot to have installed, and for $8 to $15 per square foot, you can get a floor with elaborate color staining or stamping treatments. In above-grade locations where a cement-board underlayment or structural reinforcement is required, you can expect costs to increase by $2 to $3 per square foot.
While these costs are at the upper end of most flooring materials, when you consider that the floor is likely to last as long as the house itself, concrete flooring becomes a remarkably cost-effective choice.
Concrete scores very highly in the cleaning and maintenance category. Aside from periodic sealing of the surface to prevent stains, concrete is effectively maintenance-free. For everyday cleaning, you can sweep, vacuum, dry-mop, or wet-mop as much or as little as you like. Concrete is not like hardwood or carpet, which wear much faster without regular cleaning. Just be careful with cleaning agents, as some cleaners may react chemically with the concrete and cause discoloration.
Enhances Modern-Style Decors
Modern techniques for concrete finishing now make it a cutting-edge material when it comes to home decor. Concrete can be colored by adding dye to the wet concrete as it is being mixed, or by staining/etching it with acid or other substances. And concrete can be stamped with stencil patterns to give it texture.
Few materials are better suited to modern home decor than a concrete floor with a creative finish treatment.
Disadvantages of Concrete Floors for Bathrooms
Concrete has obvious advantages as a flooring for bathrooms, but there are a few drawbacks, too. Make sure to keep these in mind as you consider flooring choices for your bathroom.
Slippery and Hard
Interior concrete floors can be finished until they have a very smooth, almost glass-like surface, and these floors can be very slippery when wet, especially if treated with a surface sealer, and especially when you are barefoot. Combine this slipperiness with a rock-hard surface and you a problem surface for bathrooms, where moisture is the rule. If you're having a new concrete slab or concrete overlay poured for a bathroom floor, make sure the finishers leave it with a little traction for safety. Do the same if you're grinding and polishing an old concrete slab to use as a finish floor.
Can Be Stained
Concrete is a naturally porous material that is highly susceptible to staining from spilled liquids. The same characteristic that allows concrete to accept a decorative stain also makes it susceptible to discoloration from chemicals. Stains are less likely to occur in a bathroom than in a kitchen, but it's still a good idea to take precautions to protect the floor. The best solution is to seal the concrete periodically with a film-forming sealer. Some sealers also add a bit of traction to the floor, which is a good option if the floor is too smooth for safety in a bathroom.
Concrete slabs tend to be colder than flooring materials laid over wood subfloors, because the slabs typically sit directly on the earth, which absorbs heat. Concrete also has a high thermal mass. This means that a cold floor tends to stay cold and warm floor tends to stay warm; in other words, concrete changes temperature slowly. If you're heating a bathroom with conventional forced-air heat, you're simply blowing warm air over the top of the floor and throughout the room, which has little warming effect on a slab that's also being chilled by the ground 24 hours a day.
On the other hand, if you're pouring a new concrete slab, you can pour the slab over insulation that serves as a thermal barrier over the ground, or install a radiant floor heating system to heat the slab and turn it into an actual heat source. Due to its thermal mass, concrete is an excellent material for in-floor heating. Radiant systems are available both as electric wire coils and as hydronic systems that circulate hot water through plastic tubing embedded in the concrete as it is poured.
The Bottom Line
Concrete has key features that make it a very good choice for bathroom floors, as well as some characteristics that make it problematic. It is a very durable, easy-to-clean, and waterproof material, but it is also a cold, hard, slippery surface that requires special solutions to work effectively as a bathroom flooring material.