The document discusses different types of shallow foundations. Shallow foundations transfer structural loads directly to soil near the ground surface. They are suitable when stable soil with adequate bearing capacity is found near the surface. The main types discussed are wall footings, isolated/column footings, combined footings, mat/raft foundations, strap/cantilever footings, and continuous footings. Construction of shallow foundations involves excavation, placing reinforcement, forming the footing, pouring concrete, curing, and backfilling.

1. SHALLOW
FOUNDATIONS

2. FOUNDATION
■ FOUNDATION IS THE LOWEST PART OF A STRUCTURE
WHICH PROVIDES A BASE FOR THE SUPER-STRUCTURE
AND TRANSMIT THE LOADS (LIVE LOAD , WIND LOAD ) ON
THE STRUCTURE INCLUDING THE DEAD WEIGHT OF THE
STRUCTURE ITSELF TO SOIL BELOW.
TYPES OF FOUNDATION : 1. DEEP FOUNDATION
2. SHALLOW FOUNDATION

3. SHALLOW FOUNDATION
 The Foundation Provided Immediately
Below The Lowest Part Of The Structure
Near The Ground Level, Transferring Load
Directly To The Supporting Soil, Is Known As
Shallow Foundation.
 Shallow Foundation Is Provided When
Stable Soil With Adequate Bearing Capacity
Occur Near To The Ground Level.
 Requirements
 Suitable Soil Bearing Capacity
 Undisturbed Soil Or Engineered Fill

4. 1. WALL FOOTING
2. ISOLATED FOOTING
3. COMBINED FOOTING
4. INVERTED FOOTING
5. CONTINUOUS FOOTING
6. CANTILIVER FOOTING
7. GRILLAGE FOOTING
TYPES OF SHALLOW FOUNDATION

5. WALL FOOTING
A Wall Footing Or Strip Footing Is A Continuous
Strip Of Concrete That Serves To Spread The
Weight Of A Load-bearing Wall Across An Area Of
Soil.
Wall Footings Consists Of Several Courses Of
Bricks, The Lowest Course Being Usually Twice
The Breadth Of The Wall Above.
The Increased Base Width Of The Wall Is
Achieved By Providing 5 Cm (½ Brick Length)
Offsets On Either Side Of The Wall. The Depth Of
Each Course Is Usually 10 Cm (Thickness Of One
Brick). In Some Cases, How Ever, The Bottom
Courses Are Made 20 Cm. (Depth Of Two Bricks)
Deep.

6. ■ A Bed Of Lean Concrete Of Uniform Thickness Is First Spread Over
The Entire Length Of The Wall. The Depth Of Lean Concrete Bed Is
Normally Not Less Than 15 Cm. And Its Projection On Either Side
Of The Wall Base Varies Between 10 To 15 Cm.
■ In Any Case, The Depth Of The Concrete Bed Should Never Be
Less Than Its Projection Beyond The Wall Base.
■ The Concrete Bed Provides A Plain Surface Upon Which The
Masonry Work For Wall Footings Can Be Started Directly. It Not
Only Rectifies The Inequalities Of Excavation But Also Bridges Over
Soft Patches In The Soil below.

7. ISOLATED OR COLUMN
■ THEY ARE USED TO SUPPORT INDIVIDUAL COLUMNS . THEY CAN
BE EITHER OF STEPPED TYPE OR HAVE PROJECTIONS IN THE
CONCRETE BASE. IN CASE OF HEAVY LOADED COLUMNS , STEEL
REINFORCEMENT IS PROVIDED IN BOTH THE DIRECTIONS IN
CONCRETE BED.
■ 15 CM OFFSET IS PROVIDED ON ALL SIDES OF CONCRETE BED.
THE FOOTING OF CONCRETE COLUMNS MAY BE A SLAB , STEPPED
OR SLOPED TYPE.
■ FOOTINGCAN BE RECTANGULAR IN SHAPE IF BOTH THE COLUMNS
CARRY EQUAL LOADS , OR CAN BE TRAPEZOIDAL IF THERE ARE
SPACE LIMITATION AND THEY CARRY UNEQUAL LOADS.
■ GENERALLY , THEY ARE CO STRUCTED LOADS OF REINFORCED
CONCRETE.

9. COMBINED FOOTING
■ A COMBINED FOOTING IS THE ONE WHICH
SUPPORTS TWO COLUMNS. IF THE
FOOTING SUPPORTS MORE THAN TWO
COLUMN , IT IS KNOWN AS A
COUNTINUOUS FOOTING .
■ THE LOCATION CENTRE OF GRAVITY OF
COLUMN LOADS AND THE CENTROID OF
THE FOOTING SHOULD COINCIDE.

10. A COMBINED FOOTING IS
PROVIDED UNDER THE
FOLLOWING CIRCUMSTANCES:
1. WHEN THE COLUMNS ARE
VERY NEAR TO EACH OTHER
SO THAT THEIR FOOTINGS
OVERLAP.
2. WHEN THE END COLUMN IS
NEAR A PROPERTY LINE SO
THAT ITS FOOTING CANNOT
SPREAD IN THAT DIRECTION.
A COMBINED FOOTING MAY BE
RECTANGULAR OR TRAPEZOIDAL
IN PLAN

11. INVERTED ARCH FOOTING
■ THIS TYPE OF CONSTRUCTION
USED ON SOFT SOILS TO REDUCE
THE DEPTH OF FOUNDATION
■ LOADS ABOVE AN OPENING ARE
TRANSMITTED FROM
SUPPORTING WALLS THROUGH
INVERTED ARCHES TO THE SOIL.

12. CONTINUOUS FOOTING
■ IN THIS TYPE OF FOOTING A SINGLE
CONTINUOUS R.C. SLAB IS PROVIDED AS
FOUNDATION OF TWO OR THREE OR
MORE COLUMNS IN A ROW.
■ THIS TYPE OF FOOTING IS SUITABLE AT
LOCATIONS LIABLE TO EARTHQUAKE
ACTIVITES

13. STRAP OR CANTILIVER FOOTING
■ STRAP FOOTING CONSISTS
OF TWO OR MORE
INDIVIDUAL FOOTINGS
CONNECTED BY A BEAM
CALLED A STRAP.
■ IT IS ALSO SOMETIMES
CALLED AS CANTILIVER
FOOTING OR PUMP HANDLE
FOUNDATION.
■ THE STRAP BEAM DOES NOT
REMAIN IN CONTACT WITH
THE SOIL.
■ SO A STRAP DOES NOT

14. MAT OR RAFT FOUNDATION
Mat-slab Foundations Are Used To Distribute Heavy
Column And Wall Loads Across The Entire Building Area,
To Lower The Contact Pressure Compared To
Conventional Spread Footings.
It Is Normally Consists Of A Concrete Slab Which
Extends Over The Entire Loaded Area.
Mat May Be Stiffened By Ribs Or Beams
Incorporated Into The Foundation.
Raft Foundations Have The Advantage Of
Reducing Differential Settlements As The
Concrete Slab Resists Differential
Movements Between Loading Positions

15. WHEN MAT FOUNDATIONS ARE
USED?■ The Structural Loads Are So High Or The Soil Condition So Poor That Spread Footings
Would Be Exceptionally Large. As A General Rule Of Thumb, If Spread Footings Would
Cover More Than 50% Of The Building Footprint Area, A Mat Or Some Type Of Deep
Foundation Will Usually Be More Economical.
■ The Soil Is Very Erratic & Prone To Excessive Differential Settlements. The Structure
Continuity And Flexural Strength Of A Mat Will Bridge Over These Irregularities.
■ The Structural Loads Are Erratic And Thus Increase The Likelihood Of Excessive
Differential Settlements. Again, The Structural Continuity And Flexural Strength Of The
Mat Will Absorb These Irregularities.
■ The Lateral Loads Are Not Uniformly Distributed Through The Structure And Thus May
Cause Differential Horizontal Movements In Spread Footings And Pile Caps. The
Continuity Of A Mat Will Resist Such Movement.
■ The Uplift Loads Are Larger Than Spread Footings Can Accommodate. The Greater
Weight And Continuity Of A Mat May Provide Sufficient Resistance.

16. TYPES OF MAT FOUNDATION
I. Flat Plate Mat
II. Plate Thickened Under Columns
III. Two-way Beam And Slab
IV.Plate With Pedestal
V. Rigid Frame Mat
VI.Piled Raft

17. flat Plate Mat – A Flat Plate Mat Is Used For Fairly Small And Uniform
Column Spacing And Relatively Light Loads. A Flat Plate Type Of Mat Is
Suitable When The Soil Is Not Too Compressible.
Plate Thickened Under Columns –
For Columns Subjected To Very
Heavy Loads Usually The Flat Plate
Is Thickened Under Columns To
Guard Against Diagonal Shear And
Negative Moments
Two-way Beam And Slab – When The Column
Spacing Is Large And Carries Unequal Loads It
Would Be More Economical If A Two-way Beam
And Slab Raft Is Used. This Type Of Mat Is
Particularly Suitable When Underlying Soil Is Too
Compressible.

18. Plates With Pedestals – The Function Of This Mat Is
Same As That Of Flat Plate Thickened Under Columns.
In This Mat Pedestals Are Provided At The Base Of The
Columns.
Rigid Frame Mat – This Type Of Mat Is Used
When Columns Carry Extremely Heavy Loads. In
Such Design, Basement Walls Act As Ribs Or Deep
Beam. When The Depth Of Beam Exceeds 90 Cm
In Simple Beam And Slab Mat, A Rigid Frame Mat
Is Referred.
Piled Raft – In This Type Of Construction The Mat Is
Supported On Piles .This Type Of Mat Is Used Where
The Soil Is Highly Compressible And The Water Table Is
High. This Type Reduces Settlement And Control
Buoyancy

19. Grillage footing
■ THIS TYPE OF FOOTING IS
USED TO TRANSMIT HEAVY
LOADS FROM STEEL COLUMNS
TO THE SOILS HAVING LOW
BEARING POWER. THIS TYPE
OF ARRANGEMENT AVOIDS
DEEP EXCAVATION AND
PROVIDES NECESSARY AREA AT
THE BASE TO REDUCE THE
INTENSITY OF PRESSURE.
■ GRILLAGE FOOTING IS MADE UP
OF ROLLED STEEL JOISTS
KNOWN AS GRILLAGE BEAMS
PROVIDED IN SINGLE OR

20. STRAP
FOOTING A Strap Footing Is A Type Of Combined Footing, Consisting Of
Two Or More Column Footings Connected By A Concrete Beam.
 This Type Of Beam Is Called A Strap Beam. It Is Used To Help
Distribute The Weight Of Either Heavily Or Eccentrically Loaded
Column Footings To Adjacent Footings.
 A Strap Footing Is Often Used In
Conjunction With Columns That
Are Located Along A Building’s
Property Or Lot Line. Typically,
Columns Are Centered On
Column Footings, But In
Conditions Where Columns Are
Located Directly Adjacent To The
Property Line, The Column
Footings May Be Offset So That
They Do Not Encroach Onto The
Adjacent Property.

21. STRIP FOOTING
■ Strip Foundations Consist Of A
Continuous Strip, Usually Of Concrete,
Formed Centrally Under Load Bearing
Walls.
■ This Continuous Strip Serves As A Level
Base On Which The Wall Is Built And Is
Of Such A Width As Is Necessary To
Spread The Load On The Foundations
To An Area Of Subsoil Capable Of
Supporting The Load Without Undue
Compaction.
■ Strip Foundations Are Used Where The
Soil Is Of Good Bearing Capacity.
■ The Key Sizes Of A Strip Foundation For
Concrete Cavity Wall Construction And
Timber Frame Cavity Wall Construction
Are Similar. The Size And Position Of
The Strip Is Directly Related To The
Overall Width Of The Wall.

22. STAGES OF CONSTRUCTION OF
FOUNDATION
1. LEVELLING OF LAND
2. TRACING OF PLAN ON SITE
3. EXCAVATION
4. CONCRETE FILLING
5. PLACING OF THE REINFORCEMENT SKELETION
6. FOOTING AND COLUMN FORMWORK
7. FILLING THE FOOTING WITH CONCRETE
8. REMOVAL OF FORMWORK
9. CURING
10.FILLING UP THE TRENCH

23. ■ FIRSTLY THE TRENCHES ARE DUG AS PER DIMENTIONS AND THEN THE CONCRETE
LAYER IS LAID ON BED OF THE TRENCH WHICH IS APPOXIMATELY 10 TO 20CM THICK
AFTER IT HARDNESS.
■ THE STEEL SKELETON IS LAID INTO THE PIT.
■ AFTER LAYING OF THE SKELETION FOOTING FORMWORK IS DONE AND THEN MIX OF
CONCRETE IS POURED INTO THE FORMWORK AND ALLOWED TO DRY.
■ THEN THE FORMWORK IS REMOVED AND CURING IS DONE.

24. ADVANTAGES OF SHALLOW
FOUNDATION It is a quick process compared to others in the construction work.
 This type of foundation is also economically cheaper than any other
foundations.
 Though there are some limitations in mat foundation still it is
economical in some cases.
 It can resist ground water absorption.
 The damage due to earthquake is lesser than any other type of
foundation.

It consists of a reinforced concrete slab which is more thicker than footin
g foundation.
 It prevents unequal settlements.

25. LIMITATIONS OF SHALLOW
FOUNDATION Spread footers being installed too shallow, oftentimes
just 2‐3 feet below a foundation, which does not
eliminate the effects of expansive soils.
 Foundation repair will last longer than a week as the
excavations are made and the concrete will have to be
cured before the holes can be refilled.
 A huge amount of earthwork is to be done in Mat
foundation. If the shoring system can not resist the
pressure of outside land, then the structure
surrounding the area may be damaged by deflection of
soil.
 Ground water may come out when the earthwork is
done. Limited to dealing with point loads. Limitations of
shallow foundation

26. THANK YOU