Updated February 3rd, 2019
As construction professionals, our responsibility is to properly construct footings as designed or suggested in the structural drawing.
In this post, I’ll show you how to construct an isolated footing for a residential building. You can do this in following 10 easy steps.
10 Steps to Construct an Isolated Footing
Follow the steps below to construct an isolated footing.
1. Positioning Footing Location
Footing layout sheet of the structural drawing shows dimension related to grid line to place the footing on the ground. See the image below.
Mark the footing on the ground as shown in the drawing.
2. Earth Excavation
Excavate a trench on earth for the footing. The size of the trench should be 1′ bigger in both sides than the footing size. In the above image, we have a footing size of 4′ x 5′. For this footing, you have to make a trench size of 5′ x 6′. It is done for placing and removing shutter easily.
The depth of a trench will depend on the earth condition or suggested in the drawing.
3. Preparing the Base
A Checklist for Brick Flat Soling
Sometimes brick-flat-soling isn’t suggested in the structural drawing. If you found the base soil isn’t suitable enough to construct the footing without brick flat soling then consult with the structural designer.
4. Making Form-work
Make a form for the footing as specified size. You can use wooden shutter or steel shutter for this purpose. Place the form as shown in the footing layout sheet of structural drawing.
Types of Formwork Materials
Check the dimension of form and check if it is properly placed related to grid lines. Also, make the form-work leakage proof.
5. Placing Reinforcement
I assume you have the required materials for the isolated footing available on the project.
Cut the steel reinforcement as required sizes and provide L-bend as shown in the structural drawing. You can make the reinforcing net for the footing separately and place in footing position later or you can place the reinforcing bar directly on footing position and bind them there.
One important thing sometimes not shown in the drawing is that – in which direction main reinforcement of footing should be placed – in short direction or in long direction?
In footing, placing main reinforcement doesn’t follow the short direction rule. It is related to the position of the column on the footing. Read the following post to know about this.
6. Providing Cover Block
It is very important to maintain concrete clear cover not only in footing but also in all RCC members. Provide required cover block in bottom and sides of the footing to keep the reinforcing net in position.
7. Placing Column’s Reinforcement
Neck column reinforcement should be placed before pouring concrete into the footing. Because neck column’s reinforcement sits on the bottom reinforcement of footing.
8. Pouring Concrete
Check again the footing and column are properly placed. Check the form of the footing is leakage proof. If everything is perfect then move to pour concrete.
If the concrete volume is large or if you make several footings to cast at a time then you can go for ready-mix concrete. Otherwise, you can cast your footing with machine mix concrete. In that case, you have to order and stacked the required concrete ingredients on the job-site before.
9. Removing Formwork
On the next day remove the form of footing. If any small honeycomb appears on footing’s surface repair those properly. If checked the formwork properly major honeycomb won’t appear.
If major honeycomb somehow appeared on the footing then you have to consider breaking the footing and reconstructing.
10. Back Filling
If everything is ok then fill the trench with soil and compact.
Now what? I think you noticed I back-fill the footing’s trench before constructing neck column. Don’t do this. Yes. Before backfilling you should construct the neck column.
If you have anything to say, write it in the comment section below.