CONCRETE REHABILITATION: STAIRS
Construction of Concrete Stairs
Construction of concrete stairs includes steps such as designing, preparing foundation, building formwork, placement of reinforcement steel bars, concreting, finishing and curing. Construction of concrete stairs is a difficult task that requires a professional to study all the aspects and design it and skilled labor to construct it.
Designing of Concrete Stairs
Designing of stairs requires through knowledge about design aspects and site study. The factors that influence the design of stairs are height of the floor, width of the stairs, risers depth, thread width, thickness of the stairs, angle of the stairs, load applied on the stairs and many other aspects which requires a qualified engineer to design the perfect stairs.
The STANDARD DIMENSIONS for STAIRS:
Component Standard Dimension
Thread 9.0 - 9.25 Inch
Riser 7.5 – 8.25 Inch
Width 3 Feet
Flight Angle 30 - 45 Degrees
The foundation on which the concrete stairs are built needs to be properly constructed so that the loads of the stairs are transferred in to ground successfully. If a plinth beam of the building is present at the start of the stairs, then the reinforcement steels bars can be connected to them which will transfer the loads. If no plinth beam is found, then a small concrete foundation or size stone masonry must be constructed, to support the stairs at the top which restricts the movement of stairs is usually done to the roof beam or slab.
Building the Form for Concrete Stairs
The most important step when building concrete stairs is to use a proper formwork. The angle of flight, dimensions of thread and riser are to be properly checked. Usually while constructing a stairs attached to wall, the line of flight , thread and risers are marked on the wall for proper fixing of shuttering or formwork.
The boards must be at least 2” thick, as to support the weight of the concrete. The whole structure of the form, must be supported by 4×4 posts. The wooden boards are used to create the steps and are fastened with several screws to the lateral structure of the formwork.
Steel Reinforcement for Concrete Stairs
The concrete steps are to be reinforced with steel bars so as it carries the loads coming upon the stairs and transfer them to the ground. The number of steel bars and size of the bars is to be calculated by a structural engineers depending upon the loads coming on the stairs.
Pouring of Concrete for Concrete Stairs
Pouring of concrete into the form is started from the below part to above. The concrete mix plays an important role in strength and durability of stairs. Standard mix used for stairs are 3 parts cement, 2 parts sand, 4 parts gravel and water. It is recommended to use a concrete vibrator while pouring the concrete to completely fill the gaps of the stairs and to avoid any honeycomb formation.
This work is to be carried out with great care and patience , as any sudden movements can disturb the alignment of the formworks or even collapse the formwork. It is always recommended to pour the concrete ceiling and stairs in the same day, as to create a strong bond between these components.
Removal of Forms
The stairs requires at least 21 days to dry out completely, so the removal of formwork is to done only after 21days. In these 21 days proper curing is to done to prevents the cracks in stairs due to thermal expansion.
After the 21 days, the formwork is removed by using a hammer and a crowbar. Work with patience, as to avoid damaging the concrete or the edges of the stairs.
Finishing of Concrete Stairs
Once the formwork is removed, the stairs can be finished in many ways as per the requirement of the use. It can just be finished using trowel or float to give concrete finish, cement tiles, granite can be installed for better appearance. Even carpet or wood can also be used to finish the stairs.
This was a multi level patio with lots of difficult angles, the form was made, the rebar is set, next we add the gravel underneath the rebar to provide a strong footing.
This has three staircases, four patios built on a multi level patio. As you can imagine, it took a bit of time to get everything lined up for the pour of concrete.
Gravel has been added. The forms are set and everything is READY TO POUR THE CONCRETE.