Concrete steps can be found in almost every home with finishes from natural gray to colored and decorative. Offered in a variety of sizes and arrangements, forming and finishing concrete steps require skill and care.
Setting Up Steps
Formwork requirements vary with the type of steps installed. Concrete steps are engineered structures often built with rebar and sometimes with wire mesh reinforcement.
Outdoor steps require compacted subgrade and proper drainage. In freeze/thaw climates, footings must extend below the frost line to prevent movement. For most new construction, foundations contractors build wing-walls off the foundation walls to support the steps. Additionally, stone should be built up under the steps to ensure a consistent thickness of concrete throughout the structure. At minimum, the concrete thickness should be 4 inches between the inside of the step to the ground. In order to determine the number of risers, divide the total height of the steps by the number of risers desired. No individual riser should be greater than 7 to 7½ inches. Check with your local code requirements for regional standards.
Formwork has to be strong enough to withstand movement during concrete placement, yet easy to remove when the steps are being finished. Treads must have slope for drainage—generally between 1/8 to 3/8 inches per foot. Formwork must be carefully staked and secured to minimize moving and distorting under the pressure of fresh concrete.
Use a low-slump concrete mix design to fill the forms. Most contractors place concrete starting at the top riser and then work down. Finishing begins where the concrete is placed first because that is where the concrete tends to set first. Consolidating the concrete during placement to reduce bugholes and honeycombing also is important. Careful removal of lumber, stakes, and nails also reduces repair work. Many finishers use screws instead of nails because less damage results when forms are removed. When the forms are removed is critical too—the best time is when the concrete no longer slumps after a form is removed. Remove one riser at a time and finish that step before continuing to the next.
Using color hardener to color and finish steps may be easier than some other options. Mix the color hardener with water to make a slurry before plastering it on the steps. The color hardener, in addition to providing a decorative treatment, also fills bugholes and honeycombing, and corrects minor elevation problems.
Other decorative applications include concrete stain, imprinting, stenciling, sand finishes, and sand-blasting with a pattern. If a natural gray is desired but the concrete does not have enough intensity, adding a little black integral pigment will help. If the gray color is inconsistent, a slurry or grout wash can even its appearance.
Using overlay cement products to provide the finished surface can make steps easier and even has its own decorative appeal. With overlay work the base concrete doesn't require elaborate finishing. Forms can be left in place until the concrete hardens to keep risers straight and true. After the concrete sets, strip the forms and face the steps with overlay material using a trowel to apply the material in the same manner as the color hardener. Depending on the choice of the overlay product, it can be tapered with a trowel to a featheredge at the nosing and at the corners, or it can be decoratively finished by stamping, staining, or adding aggregates.
Radius, Cantilever, And Step Liner
Manufacturers sell reusable plastic bender boards to accommodate radii, thus replacing the older method of bending hardboard.
Butterfield Color, Aurora, Ill., makes polyurethane cantilevered cut stone step liners, which won Concrete Construction magazine's “Most Innovative Product” award at the 2007 World of Concrete.
“To create a radius cantilevered step with the formliner, you begin with the usual process to form the radii, then attach a flexible styrene foam board below the top edge of the form,” says Joe Garceau, co-owner of Butterfield Color. “This creates a void or inset for the cantilevered form to sit on where the tread ledge emerges. The styrene may be kerfed (slit) to fit the curve of the form. Use a fluid mix design to help avoid honey combing with a low water-cement ratio and add microfibers. Carefully finish the tread at the cantilevered edge without using an edger, removing the formliners the next day. Additional color can be added with stains if desired. This system avoids the risks that occur with early form stripping.”
“I used mop heads to texture the edges and fronts of steps,” says Vince Schrementi, owner of Everlast Concrete, Steger, Ill. “The mop heads are draped over the face of the form and all four edges of the pan step. It achieved a unique natural appearance. Then, in the lower level, I enhanced an imprinted fieldstone pattern by angular forming. I used different wood lengths to complement the uneven fieldstone. After I placed the concrete, and stamped the pattern, I brought the joints down the face of the steps.” He completed the work in two placements to give a little more finishing time and create more room for framing. “I ended up with two different colors that showed on every other step. For even color, try to place concrete all at once,” he advises.
The International Residential Code (IRC) for residential construction has a section on stairs that reviews headroom, stair treads, riser heights, stair landings, and more. For more information, review the 2006 IRC code, section R311.5 available for purchase at www.iccsafe.org.
— Jeanne Fields is a freelance writer and owner of Fields Marketing, Douglas City, Calif. providing services to the decorative concrete industry.