How to Frame Concrete Stairs

Concrete Steps

Concrete stairs are framed as a box or mold for the concrete. The frame is generally constructed of 2-inch nominal framing lumber cut to size, leveled, braced and reinforced in place by stakes driven solidly in the ground. The ground must be level (or leveled) and compacted, or the natural soil must be sufficiently solid to carry the final dead weight of the concrete stairs and reinforcing steel.

Things You'll Need

• 2x8 nominal s4s (sanded on 4 sides) form lumber
• 1x3 x 24" precut foundation stakes
• 1x3 random board
• ½-inch rebar tiewire
• 8d duplex ("doubleheader") form nails
• 16d duplex ("doubleheader") form nails
• Gypsum layout chalk
• Mason's twine
• Square blade shovel
• 5-lb. or 10-lb. sledge hammer
• Electrical circular saw
• 16 oz. hammer
• Level or leveling device
• Square and other common tools

Instructions

Stair Design and Layout

1. 

   Level and Line

   Design the stairs to meet basic codes. They must be a minimum of 3 feet wide. The risers must be in an acceptable range, generally 5 to 7½ inches. The treads or steps are generally 11 to 12 inches. A typical set of concrete steps would be 42 inches wide. A minimum 3-foot by 3-foot landing must be provided at the top of the stairs and should be about 1½ inch below finished floor level. Assume the finished floor height of the house is 24 feet from a level graded lot. The finished landing height will be 22½ inches from grade. Using a 7½-inch riser (2x8 nominal board), we will end up with three risers and two treads. For our layout, we will use 12-inch treads. So the overall length of the stairs will be 36 inches (landing) + (2 treads @ 12 inches = 24 inches) = 60 inches overall concrete by 42 inches in width.

2. 

   Frame and Brace

   Level the site and compact it if necessary to support the finished weight. Using twine and batter board or offset stakes, lay out the rectangle at ground level and square the corners using the 3-4-5 method. Next dig out a minimum 12-inch x 12-inch square footing all the way around the inside of the stair perimeter. Be sure the footings are level, square and clean. Be sure the area inside the perimeter is level and clean. This form will be open against the foundation wall, which is assumed to be concrete or block. Frame a three-sided form 60 inches inside on two sides and 42 inches inside on the third side. This is the first level form. Set the form in its final location at the edge of the footings. Drive 1x3 foundation stakes vertically firmly into the ground at all form corners and mid-points, making sure that the forms remains square.

3. 

   Frame and Brace

   Using a level or leveling device, start at a point on one side of the form against the foundation wall (which is exactly 24 inches from the finished floor of the house above). Level the frame and nail it to the vertical stakes, using the 8d duplex nails. Constantly check at each stake for level. When complete, the base form will be completely level. Next frame a 2x8 three-sided form to 42 inches by 50 inches. Place this on top of the base form and carefully level and nail at each stake. Repeat the process with a third frame of 42 inches by 40 inches, which will make the landing. This landing will be 1½ inches below the finished floor of the house and will have a finished surface of 40 inches x 42 inches. The risers will be 7½ inches, and the treads will be 12 inches.

4. 

   Reinforcing Steel

   Use 8d duplex nails to nail random 1x3 boards vertically as needed to reinforce the forms and hold the three levels tightly together. Next prepare four 2x4 pointed stakes and drive them firmly into the soil against the form at the foundation wall and at the first riser. Nail them with16d duplex nails for additional strength. Now start at one end of the the form, using the twine to keep the form straight, and drive 1x3 45-degree "kicker" stakes into the soil. Brace them into the 1x3 vertical stakes. Check for line at each vertical stake. Use kickers at the top of the first lower form, the top of the mid-height form and at mid-height on the highest form. Use 45-degree temporary braces inside the forms to keep them in line awaiting the concrete pour.

5. Prepare two bars of ½-inch steel rear-formed in a rectangle to fit in the stair footings. Hang the steel from the form boards at the center of the footing top and bottom. Also, form a rebar rectangle to hang mid-height on the top form board. Take three straight bars and tie them from the top steel rectangle to the front high steel in the footing by the first riser and tie off with tie wire. Take three 22-inch straight steel rebar pieces and tie them off from the landing steel rectangle to the steel rectangle in the footing. Wet down the forms, and you are done.

Tips & Warnings

• Soil compaction is very important. Be sure that soil is well compacted or consult a soils engineer.

• Two or three riser simple stair steps can be prefabricated as a single box-like unit before setting in place to reduce time and effort. New laser leveling and line units work well for simple stair installations.

• Don't start before checking your local building codes for stair construction. Handrails may be required at specified heights. Many building departments offer standard plans for small projects like stair installations.

References

• American Concrete Institute: Advancing Concrete Knowledge

Resources

• U.S. Dept of Housing and Urban Development: MPS Supplementing Model Building Codes