Updated February 3rd, 2019
When you plan to cast footings of a building, you need to calculate concrete volume. Either you use ready mix concrete or plan to cast the footings manually you need to know the exact concrete volume. So that you won’t have excess materials after complete footing casting or you won’t run out of concrete ingredients before completing footing casting.
If you plan to use on-site machine-mix-concrete than you have some flexibility. Because if you order for excess concrete ingredients you can use those in some other concreting works. Yet, you need to calculate required concrete volume. So that you won’t run short of concrete ingredients before casting the footing.
If you plan to use ready mix concrete to cast the footings, you need to know the exact required concrete volume for ordering concrete.
Over-ordering ready-mix-concrete will cost you more. Because ready-mix supplier won’t take ordered concrete back. You will need to pay for excess concrete.
As cost is a major issue in construction, you need to control cost by not over ordering ready-mix concrete or over mixing concrete. So, calculate the exactly required concrete volume for the footings before going to cast.
In this post, I’ll show you how to calculate the concrete volume for footings of a building easily.
How to Calculate Concrete Volume for Footings of a Building Construction Project
Calculating concrete volume for footings is easy. You just need to get the volume of different sizes of footings by applying some geometric formula.
Let’s see how we can do that.
Summarising Similar Types of Footings
A building has different types and sizes of footings. They are marked as F1, F2, F3…etc.
The first thing you need to do is to summarize them all.
For example, The building has 5 numbers of F1 footing, 6 numbers of F2 footing, 4 numbers of F3 footing etc.
Counting numbers of the same type of footings from the drawing is a little bit tidy. Because you’ll forget which footing you have counted and which you didn’t.
The best way to do this is to mark the footing after counting.
Take a pencil and mark one after one when counted.
After counting all the footings in this way, check the footing layout drawing if any footing is not marked. Unmarked footing means you didn’t count that footing. If you found any footing unmarked, count that too.
After summarizing all types of footings, now calculate the concrete volume for each type.
Calculating Concrete Volume
For calculating concrete volume, you just need to get the volume of some 3D shapes.
The shapes can be square, rectangle and trapezoidal.
For example, the F1 footing is a square size footing and the dimension is 4′ x 4′ x 1′.
So, the concrete volume for this footing is 16 cubic feet.
As we have 5 numbers of footings of this type, so the total concrete volume for F1 type is,
= 5 x 16
= 80 cubic feet.
Again, the F2 footing is a rectangular shape footing and the dimension is 4′ x 6′ x 1′.
So, the concrete volume for one footing of this type is 24 cubic feet.
As we have 6 numbers of F2 type footing, so the total volume for this type of footing is
= 6 x 24
= 144 cubic feet.
Again, for example, F3 type footing is a trapezoidal shape and the calculated concrete volume for one footing of this type is 30 cubic feet (assumed).
As we have 4 numbers of F3 type footing. So, the total concrete volume for F3 type footing is,
= 4 x 30
= 120 cubic feet.
Read More: How to get the volume of a trapezoidal shape? (civilology)
Concrete Volume of Footings of a Building Construction Project
You may have other types of footings in your building construction project. Calculate concrete volume for all the different types of footings.
For keeping this post easy to read and easily understandable, I’ve just shown three types of footing.
So, the total concrete volume in footings for our example building project is,
= F1 + F2 + F3
= 344 cubic feet.
This is the exactly required concrete volume for footings of the building project.
One Dispute Regarding Concrete Volume
There is a dispute regarding concrete volume. That is, do we need to deduct reinforcement volume from concrete volume?
I didn’t find any written instruction anywhere about this.
Some say we should deduct reinforcement volume and some say we shouldn’t.
In my experience, I found that if we deduct reinforcement volume from the total concrete volume, we run short of concrete during casting.
So, my recommendation is not to deduct concrete volume from the total volume to find the exact volume.
So, how much concrete volume we found in the above calculation for the footings of our example building is the concrete volume we exactly require.
To calculate concrete volumes for footings you just need to get the volume of some 3D shapes. It is not hard if you know some geometrical formulas. After getting volume for all the different shapes, just grand total them.
Express Your Opinion
Do you deduct steel volume of RCC members to get the exact concrete volume? Please share in the comments below…