Concrete Stairs Reinforcement Details
The process of building concrete stairs involves several steps, including designing, laying the foundation, constructing the formwork, installing reinforcement steel bars, pouring the concrete, finishing, and curing. Construction of concrete stairs is a difficult task that requires both skilled labor to build it and an engineer to research all the factors and design it.
Making an excellent staircase is not an easy task. You need to consider various factors such as the weight of the person who will use these stairs and location of building units where they will be used. If you plan to build a reinforced concrete staircase in your home or office, then you must ensure that there are no cracks or other defects in it otherwise it will become unsafe for its users.
Reinforced concrete staircase detailing is similar to reinforced concrete slab detailing.
Reinforced concrete staircase reinforcement details are similar to reinforced concrete slab detailing. The main difference is that the floor-to-floor height of a reinforced concrete staircase is greater than that of a slab and therefore requires more vertical bars. The footing is also different; it’s like a column due to its larger diameter and weight (vertical bars) compared to slabs or horizontal bars.
Reinforced Concrete Stair Detailing
Dowel bars are provided on the top and bottom landings that will serve as the main reinforcement of the stairs.
The bottom dowel will serve as the top main bar of the stair, and the top dowel will be the bottom main bar of the stair that will be spliced with a minimum of 40x the diameter of the rebar.
Distribution bars are provided perpendicular to the main reinforcement. Also, nosing bars are placed to provide reinforcement to the steps.Straight-run stairs typically have the following measurements: a stair width of 36 inches (91.4 centimeters); a stair tread depth of 11 inches (28 centimeters); a stair riser size of 7 inches (18 centimeters); and a length of 10 feet (3 meters) from the bottom to the top of the stairs.
Stair Width Dimensions
The width of a staircase is measured from side to side. There is a standard set by the International Residential Code and other regional and local building codes, and this standard is typically 3 feet or 36 inches wide or wider. The handrails are not part of this size.
The best part is that these dimensions are frequently flexible, so if you meet the minimum feet, you can go as wide as you want with your stairs, depending on the size of your home, your budget, or your wants.
Stair Tread Dimensions
The horizontal surface you step on as you ascend and descend a staircase is known as the stair tread. The front edge of the nosing to the other front edge or nosing of the other step is measured to determine the tread depth.
If you have a stair nosing, this distance, which is measured horizontally, needs to be at least 10 inches. The longest tread you can have without a nosing is 11 inches.
The depth of the stair tread should allow you to step on the stairs with most of your feet. It’s crucial to get this size correct and as accurate as you can, especially when going down stairs, to prevent accidents.
Stair Stringer Sizes
The stringer board, also known as the stair stringer, is what supports the sides of the staircase. You can tell it apart by its saw-tooth-shaped sides, though occasionally it may just be one single, sturdy straight structure.
The risers and treads are attached to and secured to the stair stringer. The stringer must be at least 3.5 inches thick to stably support the stair structure.
Stair Riser Sizes
We must first understand what a stair riser is, which is the vertical portion of the step. It is the distance you cover going up or down the stairs.
Each step or stair riser should be separated by no more than 7 3/4 inches. In order to prevent accidents, this standard was established to ensure that the stairs wouldn’t be too high or too low.
If you choose open risers for your staircase, you must ensure that the space will not be greater than 4 inches; it must be 4 inches or lower.
Stair Landing Dimensions
The width of each landing will not be exactly the width of the flight of stairs served. Each landing will have a base element that is 36 inches (914 mm) in length when measured toward movement. Riser heights between 150 mm and 200 mm are the most extreme.
The ideal tread length is between 250 and 300 mm. The step’s length should be at least 600mm. The handrail should be at least one meter tall for each flight of stairs.
There will never be a staircase with an upward ascent greater than 12 feet (3658 mm) between floor levels or landings.
Read Also: Types of Stairs
Construction of Concrete Stairs in Steps
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.