IMPORTANCE OF FOUNDATION ITS TYPES AND USE

1. DATE: 12/18/2022

2. CHAPTER 1: FOUNDATION AND THEIR TYPES

3. WHAT IS FOUNDATION ?
• A foundation is the lowest and supporting layer
of a structure.
• is the lowest artificially prepared part of the
structure that is in direct contact with the ground
and that transmit the load of the structure to the
ground
• is the substructure of the building

4. WHAT IS FOUNDATION ?
Super-structure
Sub-structure
Foundation
Basement
G+upper floors

5. FOUNDATION
Isolated footing Combined footing
Mat footing

6. FUNCTION OF FOUNDATION
• to bear and support the structure
• distribute the load of the building to the ground
• Anchor/secure the structure against natural
forces such as earthquakes, wind, rain etc
• to isolate it from ground moisture
• to prepare a level surface for masonry work

7. TYPES OF FOUNDATION
I. Shallow foundation
II. Deep foundation
i. SHALLOW FOUNDATION:
• Is the foundation that are provided immediately
beneath the lowest part of structure near to the
ground level
• shallow if its depth is equal to or less than its
width or if the depth is less than 3m

8. i. Shallow foundation:………………………
• These foundations are mostly placed on the first
hard and firm strata available below the ground
level
• These type of foundations are used when surface
soils are sufficiently strong and stiff to support the
imposed/forced loads
• Generally unsuitable in weak or highly
compressible soil as poorly compacted fill,
alluvial deposits etc

9. i. Shallow foundation:………………………
Various
shallow
foundation

10. ii. DEEP FOUNDATION:
•when the depth of the foundation is more than the
width of the footing
•generally adopted for bridge piers etc

11. TYPES OF SHALLOW FOUNDATION

12. 1. Spread footings
a. Single footing
b. Stepped footing
c. Sloped footing (RCC)
d. Wall footing without step
e. Stepped footing for wall
f. Grillage foundation
2.Combined footings
a. Rectangular combined footing
b. Trapezoidal combined footing
c. Combined column-wall footings
3. Strap footings
4. Mat foundation
a. Solid slab system
b. Beam slab system
c. Cellular system
TYPES OF SHALLOW FOUNDATION:
pad footing/isolated footing
Wall footing/ strip footing

13. 1. Spread footings
•Spread footings are those which generally supports
one wall or one column
•Spread footings are those which spread the super-
imposed load of wall or column over a larger area.
•Foundations constructed by increasing the area at
the base of the structure by means of offsets are
called spread footing

14. 1. Spread footings…………….
Types:
a. Single footing
b. Stepped footing
c. Sloped footing
d. Wall footing without step
e. Stepped footing for wall
f. Grillage foundation
pad footing/isolated
footing
Wall foundation/
strip footing
In above a. b. c. if columns are of brick these are known
as masonry pillar footing and if the columns are of
concrete than these are reinforced concrete footing)

15. 1. Spread footings…………….
•Pad/isolated footing: is the one which provides
footing for a single column or a wall
•Strip footing: is the one which provides footing for a
continuous wall
•RCC footing: these may be stepped or sloped like
pad footings in order to support heavy loads,
reinforcement is provided at the base

16. b b
B B
Fig: concrete column footing/ reinforced concrete

17. a. Single footing: isolated/pad footing or RCC
•shows a single footing for a column, in which the
loaded area (b x b) of the column has been spread to
the size B x B through a single spread
• The base is generally made of concrete
In brick columns:
•The offset is generally 10 to 20 cm
•The base should not be less than the offset(in case
of cement concrete the base should be equal to
offset and in lime concrete 3/2 of offset)

18. b. Stepped footing: isolated/pad footing or RCC
•shows the stepped footing for a heavily loaded
column, which requires greater spread or when soil
bearing pressure is less
•The base of the column is made of concrete
•In case of brick pillar offset should not exceed 5cm
•In case of masonry pillar the offset is 10 to 15cm
• the height of each step 15cm to 22.5cm

19. c. Sloped footing: RCC
•shows the case in which the concrete base
does not have uniform thickness
•but is made sloped, with greater thickness at its
junction with the column and smaller thickness at the
ends
•Since concrete can be mould in any shape, sloped
footing is possible in RCC

20. d. Wall footing without step: (strip footing)
•This type comes
under the wall
foundation/ strip
foundation and is the
simplest type of
footing
•shows the spread
footing for a wall
•Consisting of
concrete base
without any steps
t
3t

21. d. Wall footing without step: ………….(strip footing)
•This footing is applicable when the wall carries light
loads or when safe bearing pressure is very high
•The wall directly rest on the concrete base with no
offsets
•The projection of the base varies from 10cm to 20
cm
•as a thumb rule the width of concrete base should
not be less than twice the width of the wall

22. e. Stepped footing for wall:(strip footing)
•Usually masonry
walls have stepped
footings with a
concrete base
•Offsets are provided
at the base of brick
wall (offsets are
generally one fourth of
brick length)
t
j
j
2(t+j)

23. e. Stepped footing for wall: ……….. (strip footing)
•In case of brick walls the offsets does not exceed
5cm; the corresponding height each step would be
10cm
•In case of stone masonry offsets are provided upto
10 cm and height of each step 15 to 20cm
•When wall carries heavy load and the safe bearing
pressure is not very high

24. •In the above figure :
t: thickness of wall
j: projection of concrete bed at the base

25. f. Grillage foundation:
•Is a type of isolated footing provided for heavily
loaded steel foundations especially in those
locations where the bearing capacity of soil is poor
•The depth of foundation is limited to 1m to 1.5m
•The load of column or stanchion is distributed to a
large area with the help of tiers of joists
•Tiers are placed right angle to the tier at next level
•Tiers are wooden or rolled steel section(I-section)

26. f. Grillage
foundation

27. f. Grillage foundation:…………….
•Grillage foundation avoids deep excavation and
provide necessary area at the base of structure to
reduce the intensity of pressure
•Types of grillage foundation:
Steel grillage foundation
Timber grillage foundation

28. Steel grillage foundation:
•These foundation are constructed of rolled steel
joists(R.S.J)
• joists are provided in two tiers placed at right angle
to each other
•At each tier the joist(steel beam) are held in position
with the help of 20mm diameter spacer bars
•The grillage beams/ joist(steel beam) are
embedded in concrete however concrete do not take
the load

29. Steel grillage foundation:

30. Suitability of steel grillage foundation:
•For structures like columns, pier, foundations
subjected to heavy loads
•Employed to foundations of buildings as theatre
and town halls
Steel grillage foundation are provided for a masonry
wall on a soils of low bearing capacity

31. Timber grillage foundation:
•Provided for heavily loaded timber column or
masonry wall
•Instead of steel joists timber planks and timber
beams are provided
•Useful in water logged areas and when bearing
power of soil is very low
•In water logged areas the steel may be corrugated
•Unlike steel grillage foundation , concrete is not
embedded in timber beam

32. THANK YOU