How to pour concrete steps
Poured concrete steps provide a strong and durable transition between an exterior surface, such as a patio, and the entrance to your home. However, one of the most confusing questions that comes up is how high and how deep (front to back) each step should be. The answer to this question lies in some simple math that you can use to calculate the drive’s rise and run.
When considering the total travel of the unit, local codes often require the top landing to extend at least 12 inches beyond the door swing. Subtract the width of an outward-swinging door (usually 32 or 36 inches) from the length between the foundation and the outside edge of the steps. If the remainder is less than 12 inches, you may need to change your plan.
Know the codes before you start planning the steps. If you don’t build them up to code, a building inspector can have you tear them down. Codes may also have something to say about the placement of rebar or other reinforcement, as well as the concrete mix you use.
Expect to spend two to three days to plan, design, and perform three steps (not counting curing time).
measure rise and run
Measure the height and run of the site and stake out to indicate where the base of the bottom step will be when poured. Calculate the unit rise and run of the steps, and draw a dimensioned sketch.
How to Calculate Rise and Run
The unit of height and the unit of travel of the steps are the individual dimensions of each riser and each tread.
To calculate the rise and run of the unit, first divide the total rise by 7, a standard step height. Round fractional results to the nearest whole number. Then divide the total increase again by this number to get the unit increase.
For example, here’s the math for a total rise of 20 inches: 20 inches/7 inches = 2.8, rounded = 3 steps. 20 inches/3 steps = 6.6 inches. In this example, you will need three 6-5/8-inch-high steps to climb 20 inches.
Next, divide the total travel (to the outside edge of the door sweep) by the number of steps to run the unit. For example, if your total run was 48 inches, here’s the math: 48 inches/3 steps = 16 inches per tread. However, a 16-inch tread depth would feel too long. Set the tread depth to 13 inches, a more comfortable measurement, and make the total travel 39 inches.
Layout of foundations
Lay footings 3 inches wider than steps. Excavate the foundation to the depth required by code, for concrete, and insert 12-inch-long rebar 7 to 8 inches into the foundation. The top of the rebar should be approximately 2 inches below the finished height of the steps. Let the foundations cure, then dig a 4-inch trench between them and fill with packed gravel.
How to anchor concrete steps
With an underlying grid of 1/2-inch rebar, the poured concrete steps will provide years of low-maintenance service. Some local building codes may require you to anchor the concrete steps to the foundation wall. You can drill at an angle into a poured concrete base or through a cinder block wall and insert rebar into the holes.
Using your blueprint and the actual dimensions you’ve calculated and sketched, draw the outline of your steps on a sheet of 3/4-inch plywood. Draw the line for the landing so that it slopes 1/4 inch per foot. Fasten a second sheet of plywood to the first, with the edges flush, and cut the outline of the step with a jigsaw.
Check square, level and plumb
Using a framing square to make sure the forms are perpendicular to the house foundation, set the forms in place and run support stakes across them. Make sure the forms are plumb and level with each other, then attach them to the stakes with 2-inch screws. Cut off any portion of the stakes above the forms.
Install vertical forms
For each rung, cut a piece of lumber 2x the width of the stairs and rip to the height of the unit rise if necessary. Bevel the bottom edge of each riser (except the bottom one) to make it easier for the tread to float when you pour the steps. Attach the top vertical framing to the outside of the side framing with three 2-inch screws. Then install the remaining riser forms.
Cut braces at an angle and attach them to the side forms at the leading edge of each step. Then drive 2×4 stakes into the bottom of the braces. Plumb the side forms and fasten the braces to the stakes. To prevent the riser forms from bending, drive a 2×4 stake 18 inches or deeper into the ground in front of the steps. Attach a 2×6 to the risers and attach to the stake and battens attached to the risers. Attach an expansion strip to the base with construction adhesive.
How to build perpendicular steps
The steps may run directly from an exterior door or at right angles to it. The shapes for the perpendicular steps are combined in essentially the same way as the straight steps illustrated on these pages.
Draw a level line on the foundation to mark the height of the landing. Measure from this line to lay out the plywood forms for the back and sides. Reinforce the forms with stakes, cut beveled risers, keep them level and mark their bottom corner on the foundation. Then attach the diagonal brace to the house and the foundation and risers to the battens. Brace the leading edge of the risers as you would a straight stair.
fill with debris
To save concrete, time, and money, shovel clean pieces of broken concrete debris, river rock, or any clean masonry into the space inside the forms. Pile the debris under the landing higher than the first step, but don’t put so much debris that it makes the concrete on the steps too thin.
Add reinforcement bar
To strengthen the concrete, bend 1/2-inch rebar to roughly match the shape of the rubble mound and place over the rubble at 12-inch intervals. Wire perpendicular lengths of rebar through the first few pieces. Then raise the rebar and support it on dobies or balusters that you connect with wire to the rebar.
Mix and fill with concrete
Cover the forms with a release agent. Mix the concrete and bring it to the site in wheelbarrows. Shovel the concrete into the forms, starting with the bottom step and working your way up. Hit the sides of the forms and risers with a hammer and tap a 2×4 up and down into the mix to drive out any air bubbles. Give the concrete enough time to settle between the pieces of debris and add more concrete if necessary.
Run an edger along the inside edge of each riser to round off the leading edge of each stair to minimize chipping. If you are going to cover the steps with brick, tile, or stone, keep the edges straight.
Let the concrete set long enough to support its own weight, then remove the rising forms and finish the concrete with a trowel. Use a stepped trowel (a drywall knife works too) to smooth out the corners. Sweep the steps to roughen the surface, let the concrete cure, then install the railing. After 12 to 24 hours, remove the side forms and fill any voids in the concrete.