To construct concrete stairs, you have to know how to build the form work, mix the concrete ingredients in the proper proportions, and pour the concrete to allow for the curing process to begin. While the process sounds complicated, this article will help you make your own concrete steps like a professional mason. Follow the guide below to make exterior concrete stairs that begin at a finished first floor and extend to a grade level.
Step 1 – Design the Stair Dimensions
The first step is to determine the size of each stair and other components by obtaining the overall dimensions. A step consists of a riser, or the vertical face, and a tread, or the horizontal surface.
Calculating Risers, Vertical Faces, and Tread Measurements
Measure from the first floor level down to the grade level, and divide that number into risers of equal height, providing that the riser height doesn’t exceed local building codes. A standard vertical height of 30 inches would give room for four risers each, at 7 1/2 inches.
However, the standard horizontal length of the stairs is more arbitrary. Shoot for treads that are 11 inches or greater in width to provide a comfortably sized step.
Calculating Number of Treads
The number of risers will determine the number of treads, as the number of treads is always one less than the number of risers. Therefore, three treads at 11 inches with give an overall horizontal length, or a total run, of 33 inches.
Calculating Foundation Measurements
The stairs will require a foundation, which is typically a slab poured to a depth of 6 inches below the grade level. The foundation must have a perimeter equal to the footprint of the stairs, or the total run multiplied by the total width of the stairs.
Step 2 – Build the Form
You can build form work, usually made with scrap or low-grade lumber, by using plywood or structural framing members, like 2x4s and 2x6s. To begin, lay and cut the side forms with a saw according to the tread and riser calculations, so that they resemble a 2-dimensional side elevation of the stairs.
Fastening the Forms
Fasten the forms tightly and securely to the building’s foundation, so that the new steps will bond to the foundation wall in a seamless connection. Use wooden stakes as braces to resists the outward thrust of the poured concrete in the following steps. Nail the stakes every 12 inches along the outer surface of the form.
Installing the Riser Faces
Next, install the boards that will form the face of the risers. These boards should have a width equal to the height of the risers. Add bracing to the center if needed, and use a level to ensure the forms are plumb and the surface of the treads are level.
Step 3 – Mix the Concrete
Because the volume of concrete you will need is small, you can mix it manually. You can purchase the concrete pre-mixed, or you can use four basic ingredients to mix your own: Portland cement, sand, aggregate, and water.
Mixing Your Own Concrete
If you’re mixing your own concrete, add water as needed to the mix of other ingredients. More water will make the mixture more workable and fluid, while less water will make the concrete stronger. A good rule of thumb when mixing concrete is to use 6 gallons of water per bag of cement.
Step 4 – Pour the Concrete
Start at the bottom step and pour concrete one step at a time. Once you've poured the concrete, spread it evenly throughout the form. Spade the mix to remove trapped air.
Step 5 – Finish the Stairs
There are several finishing methods you can employ to achieve a smooth surface. You can install a screed board and work it from front to back in a side-to-side motion to drag excess concrete from the treads. Or, you can use a wooden float to get an even, level surface. Hand-trowel the area for an even finer finish.
Whichever method you choose, keep the concrete damp for up to a week after pouring it. Protect it from rain during the initial curing process, too. Once the concrete has set, you can remove the form boards.