The following are the steps for building concrete stairs:

1. Designing a concrete staircase

Stair design necessarily requires a comprehensive understanding of design principles as well as a deep knowledge of site analysis. The height of the floor, the width of the stairs, the depth of the risers, the width of the thread, the thickness of the stairs, the angle of the stairs, the load on the stairs, and many other factors must be taken into account when designing the perfect staircase.

2. Foundation and Support for Concrete Stairs

In order for the loads of the stairs to be successfully transferred into the ground and to resist stair movement, the foundation upon which the concrete stairs rest must be properly constructed. 
At the bottom of the stairs, if the building’s plinth beam is present, reinforcement steel bars can be connected to it to transfer loads. If no plinth beam can be found, a small concrete foundation or size stone masonry is built. 
It is typically done to the roof beam or slab to support the stairs at the top that restrict the movement of stairs.

3. Building the Form-work for Concrete Stairs

Using the right formwork is the most crucial step when building concrete stairs. The riser, thread, and angle of flight must all be properly inspected. Typically, when building stairs attached to a wall, the line of flight, thread, and risers are marked on the wall to ensure proper shuttering or formwork fixing. 
To support the weight of the concrete, the boards must be at least 2 inches thick. The entire structure of the form must be supported by 4×4 posts. The lateral formwork structure of the formwork is secured to the wooden boards that are used to construct the steps using a number of screws.

4. Steel Reinforcement for Concrete Stairs

Steel bars should be added to the concrete steps to strengthen them so that they can transfer loads coming up the stairs to the ground. A structural engineer must determine the size and number of steel bars based on the loads that will be placed on the stairs. 
These steel reinforcement bars are tied together and placed in the formwork with a minimum spacing of 25 mm.

5. Pouring of Concrete for Concrete Stairs

Concrete is poured into the formwork in layers, starting below and moving upward. The concrete mix is important in order for stairs to be strong and durable. The typical stair mix consists of 3 parts cement, 2 parts sand, 4 parts gravel, and water. 
To completely fill the spaces between the stairs and prevent the formation of honeycombs, it is advised to use a concrete vibrator while pouring the concrete.

This work must be done slowly and carefully because any sudden movements could cause the formwork to collapse or cause it to lose its alignment. The concrete ceiling and stairs should always be poured on the same day to ensure a solid bond between the two.

6. Removal of Formwork 

The removal of formwork must wait at least 21 days after the stairs have dried completely before it can be done. To avoid stair cracks caused by thermal expansion, proper curing must be done during these 21 days. 
By using a hammer and crowbar after the 21-day period, the formwork is removed. Be patient and careful to avoid damaging the stair edges or the concrete.

7. Finishing of Concrete Stairs

After the formwork is taken off, there are numerous ways to finish the stairs depending on the intended use. Cement tiles and granite can be installed for better aesthetics, or it can simply be finished with a trowel or float to give concrete a finish. The stairs can also be finished with carpet or wood.