1. Forms for Concrete Footingsby
Er.P.Magudeaswaran
Assistant Professor(Sr.Gr)/CE
Sri Ramakrishna Institute of Technology,
(Autonomous)
Coimbatore

2. Forms for concrete footings.

3. The studs and plates can be made from 2 × 4, or 2 × 6 lumber, depending on the size and species of lumber used for the forms and the pressure from the concrete.
If the footing is 18 in. deep, the maximum footing width will be less than 5 ft, using 2 × 4 plates for the species of lumber commonly used in formwork.

4. Slide Title
Where the size and depth of a footing produce excessive compression stresses between the pin and the wood in the bottom plate, 1- by 4-in. vertical planks can be nailed to the plates, as shown in Figure, to increase the strength of the joints, or nails can be used to supplement the strength of the pins.

5. The top view of Figure shows that, by starting with long top and bottom plates on opposite sides of the forms, the length of a footing may be increased while the width remains constant.
By adding strips of plywood, adequately attached to the plates, the forms can quickly be converted to larger sizes. A similar method can be used to increase both dimensions of a footing. In general, it is better to use the forms for the smallest footings first, and then go to the next larger sizes. However, the forms may also be used in the reverse order.

6. Additional Forms for Concrete Footings
There are many types of forms that can be used for concrete footings, depending on the footing shape, as described in the following sections and illustrated in Figures 8-6 through 8-10.

7. Forms for large size concrete footings.

8. The Above Figure shows a plan and elevation view that is sometimes used for square or rectangular footings whose depths vary from 12 to 36 in.
For footing depths up to 24 in., .-in. Plyform sheathing is supported by 2 × 4 studs, spaced at 12 in. center to center.
For 36-in.-deep footings, 7⁄8-in. Plyform with 2 × 4 size lumber is used.
The forms should be adequately braced.

9. Additional strength can be obtained by using vertical strongbacks, as illustrated inbove Figure.
If strongbacks are used, form ties should be installed between strongbacks on opposite sides of the footing, as shown in the top view of this plan.

10. Forms for stepped footings.

11. Figure 8-7 illustrates a set of forms for constructing a stepped footing.
The forms for the lower and upper sections are made in a conventional manner, with the upper form supported in the proper location on the lower form, using two pieces of 2 × 4 lumber attached to the bottom of the upper form, with the 4-in. face vertical.
Form ties should be used if and where they are needed.

12. The lower form is filled, and the concrete is allowed to set until it is stiff enough to resist the hydrostatic pressure from the concrete in the upper form, after which time the upper form is filled.
Caution must be taken to prevent an unwanted cold joint.

13. Forms for a large-diameter job-built round footing.

14. Concrete pressure on footing form.

15. Template for anchor bolts

16. THANKYOU