Introduction of stepped footing
A stepped footing is a footing that has several steps according to the load on the column. Stepped footing may be isolated or combined according to the soil condition of the construction site. In this article, we will discuss complete stepped footing detail.
Generally, isolated footing is provided where the soil-bearing capacity of the site is high, and combined stepped footing is provided where the soil-bearing capacity of the site is low.
The strength of the stepped footing of the structure is provided according to the load of the superstructure at different sections.
Why we require stepped footing detail
stepped footing detail is required for the following reasons,
- To get information on the grade of reinforcement in the stepped footing.
- To get the strength of concrete to be used.
- To get the cutting length of each piece of rebar used in footing.
- To get an idea of the dimensions of footing, i.e., the length, width, and depth of the footing.
- It provides the details of the spacing of the rebar as well as the development length to be provided.
- It shows the clear cover to be provided between concrete and rebar. etc.
Advantages of stepped footing
Different types of footing are used in the construction. Each of them has its own advantages. They are constructed according to the requirements by analyzing the structure. Some of the advantages of stepped footing are given below.
- It distributes the load of the superstructure evenly to the soil.
- It is economical and more stable than other types of footing
- It is easy to concrete them step by step since they are generally square and rectangular in shape.
Stepped footing detail drawing
Step footing reinforcement details
Step footing reinforcement calculation
Now, here we will see how to calculate the reinforcement for stepped footing step by step.
Q) How to calculate the quantity of steel from stepped footing detail given below?
Here, It is given, the width and length of the footing is 4 feet x 4 feet.
Step1: Calculate No of steel bars in each side
Step 2:- Find the total length of the Rebar
Total number of steel rods = 9+9 = 18 Nos
Length of each steel rod = 4’+2 Sides Hook
= 4’+2 x 6″ (provided hook length is 3″)
= 5 feet.
Total length of steel = 5 x 18 = 90 feet
Step 3:- Calculate the total weight of the Rebar
Finding total weight of steel = 90/3.28 = 27.43 m
The formula of find the Weight of steel
Hence, The total weight of rebar in stepped footing will be 25 Kg.
Step footing concrete calculation
How to calculate the volume of concrete in stepped footing detail given below?
Step 1: Calculate the volume of concrete of each steps
a) Volume of step-1,
Volume 1 =Length x weight x Depth
=4’ x 4’ x 0.83
=13.28 cubic feet
b) Volume of step-2,
Volume2 =Length x weight x Depth
Volume = L x W x D
= 3’ x 3’ x 0.83’
= 7.47 cubic feet
c) Volume of step-3,
Volume3 =Length x weight x Depth
Volume = L x w x D
= 3.32 cubic feet
So, Total volume of concrete,
Total volume of concrete = 13.28 + 7.47 + 3.32
= 24.07 cubic feet
Step 2: Convert the volume of concrete from cubic feet to cubic meters.
= 24.07 x 0.0283
= 0.681 cum
Step 3: Convert the wet volume of concrete to the dry volume.
Let us consider the grade of concrete = M20 = 1:1.5:3
Dry volume = 1.54 x 0.683 = 1.048 cum
Step 4: Calculate the quantity of cement, sand and aggregate
Stepped footing construction procedures
Step: 1 First of all compact the soil below the stepped footing.
Step: 2 Now provide solling of bricks or stone of a thickness of not more than 4 inches or 100 mm.
Step:3 Apply PCC ie. a mixture of cement, sand, and aggregate not less than M20 grade of concrete
Step:4 Provide a proper clear cover of a minimum of 50 mm to the concrete footing.
Step 5: Lay reinforcement of the footing according to the design on the PCC.
Step:6 Provide shuttering or formwork to provide the stepped shape of the footing.
Step:7 Pour Concrete into the reinforcement. Remember that the height of pouring concrete should not be more than 1.5 meters.
Step 8: Compact it properly with the vibrator. Over-compaction in concrete may cause segregation in footing and make it weak.
Step:9 Now, Leave it for 1 day until the final setting time of the concrete.
Step: 10 Cure the footing until at least 14 days after construction. Don’t be hurrying; proper curing is necessary for concrete to get proper strength. Curing helps to balance the hydration process in concrete and prevent cracking.
Step: 11 Finally, it is ready to carry the load. Now you can continue the further process of construction on it like brickwork, beams, etc., if required.
I hope this article on stepped Footing detail remains helpful for you. Please do share this article to preserve it for future knowledge.