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Individual 'Pad Footing' Table
Tables are shown for f'c Concrete at 2000 psi and 3000 psi
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.
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f'c = 2000 psi Concrete
psi = pounds per square inch
Footing Width = Square Footings, where
Both sides of Footing have same dimension
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f'c = 3000 psi Concrete
psi = pounds per square inch
Footing Width = Square Footings, where
Both sides of Footing have same dimension
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Maximum
Soil
Pressure
(lb/sq.ft.)
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Plate or
Column
Width
(inches)
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Allowable
Load on
Footing
(kips)
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Footing
Thickness
(inches)
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Footing
Width
(inches)
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Reinforcing
Each Way
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Allowable
Load on
Footing
(kips)
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Footing
Thickness
(inches)
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Footing
Width
(inches)
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Reinforcing
Each Way
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1500 psf
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8"
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12.4
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10"
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3'-0"
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3 No. 3
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12.4
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10"
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3'-0"
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3 No. 3
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8"
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16.8
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10"
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3'-6"
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3 No. 4
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16.8
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10"
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3'-6"
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3 No. 4
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8"
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22
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10"
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4'-0"
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4 No. 4
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22
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10"
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4'-0"
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4 No. 4
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8"
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28
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10
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4'-6"
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4 No. 5
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28
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10"
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4'-6"
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4 No. 5
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8"
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34
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11"
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5'-0"
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5 No. 5
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34
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10"
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5'-0"
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6 No. 5
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8"
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48
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12"
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6'-0"
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6 No. 6
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49
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11"
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6'-0"
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6 No. 6
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8"
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65
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14"
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7'-0"
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7 No. 6
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65
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13"
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7'-0"
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6 No. 7
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8"
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83
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16"
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8'-0"
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7 No. 7
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84
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15"
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8'-0"
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7 No. 7
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8"
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103
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18"
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9'-0"
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8 No. 7
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105
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16"
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9'-0"
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10 No. 7
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2000 psf
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8"
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17
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10"
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3'-0"
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4 No. 3
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17
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10"
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3'-0"
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4 No. 3
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8"
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23
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10"
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3'-6"
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4 No. 4
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23
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10"
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3'-6"
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4 No. 4
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8"
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30
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10"
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4'-0"
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6 No. 4
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30
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10"
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4'-0"
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6 No. 4
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8"
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37
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11"
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4'-6"
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5 No. 5
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38
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10"
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4'-6"
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6 No. 5
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8"
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46
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12"
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5'-0"
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6 No. 5
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46
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11"
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5'-0"
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5 No. 6
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8"
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65
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14"
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6'-0"
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6 No. 6
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66
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11"
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6'-0"
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7 No. 6
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8"
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88
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16"
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7'-0"
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8 No. 6
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89
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15"
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7'-0"
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7 No. 7
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8"
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113
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18"
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8'-0"
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8 No. 7
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114
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17"
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8'-0"
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9 No. 7
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8"
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142
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20"
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9'-0"
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8 No. 8
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143
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19"
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9'-0"
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8 No. 8
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10"
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174
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21"
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10'-0"
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9 No. 8
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175
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20"
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10'-0"
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10 No. 8
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Caution!
Care needs to be taken when using the tables. You must be sure of what type of
loading you are going to place over the footings and what is the soil bearing
capacity. If you do not know, be sure to ask your Engineer or Architect.
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Definitions:
f'c = 2000 psi (Concrete Strength), Example: When Ordering Concrete, simply
specify 2000 psi concrete, or what ever is the required Concrete you will be
using.
Soil Pressure = the capacity of the soil to resist a load placed on it.
Column or Plate Width = The Square size of the Column or Plate that will be in
contact with the top of the Footing.
Allowable Load on Footings = This is the Total Load that comes down the Column
to the top of the Footing.
Footing Thickness = How thick the Footing must be from the top of the concrete
to the bottom of the concrete.
Footing Width = How wide and how long the Footing must be. These Footings are
square footings, which means they have the same dimension on both sides.
Reinforcing Each Way = The size and the number of steel reinforcing bars that
are required in each Pad Footing.
For Example: 4 No. 5 means use 4 steel bars (rebars) of the number 5 size.
The placing of the rebars are to be a mimimum of 3 inches from the dirt on the
bottom of the Pad Footing and 3 inches clear of the side dirt walls. The bars
are placed in a checker board pattern and tie together with bailing wire at the
points where they intersect. The spacing between each rebar should be equal.
A piece of concrete block or a metal piece, called a chair, should support the
rebars at least 3 inches off the bottom of the hole for the Pad Footing. Pad
Footings must be physically connected to a Column. The type of Column used
will require that you install either dowels (bent steel rebars extending from
the Pad Footing into the Concrete Column) or J-Bolts if you are using a Steel
Column with a Steel Plate. Once all of this is done, you need to call the
Building Department to request for a Footing Inspection.
Once the Footing has been inspected by the Building Official and he or she
approve the installation, you may now call the Concrete Plant to deliver the
Concrete for you Footing. If you intend to make your Concrete, be sure to
speak to your Building Official, because the Strength of the Concrete is based
on the proportions of mixture of cement, sand, aggregate (rocks) and water.
Any variation in the mixture content will change the Strength of the Concrete,
so be careful. Check if your Building Department will allow you to use a
Premixed Concrete which come in bags and can be purchased a local Lumber Yard
or Hardware Store. When using Premixed Concrete Bags, you must be aware of how
much water you can add to the Premix, since the amount of water will also
affect the Strength of the Premixed Concrete.
Loading Conditions: (where, psf = Pounds per Square Feet = lb/sq.ft.)
The design of footings requires that you know what is the capacity of the soil.
The tables shown are for two assumed soil bearing capacities (1500 psf and 2000
psf). If your soil has a larger bearing capacity, you will find that when you
have the Loads Calculated, the footing size will be smaller. If you do not
know what the soil capacity is for your project, be sure to get help.
These Tables are to be used to Estimate the Footing Needed for Construction and
MAY ONLY BE USED FOR DESIGN BY SOMEONE WHO HAS THE KNOWLEDGE AND EXPERIENCE IN
CONSTRUCTION.
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For Standard Wall Footings, the Sizes and Reinforcing Vary based on the Load Transferred by the Wall to the Foundation and the Soil Bearing Capacity.
The Soils and their Bearing Capacity vary throughout the Country. The Soils may vary from place to place.
Soil is the thin layer on the surface of the Earth on which the living beings of the earth survive since it is the layer of materials in which plants have their roots.
Soil is made up of many things like weathered rock particles and decayed plant and animal matter.
It takes a long time for soil formation and more than thousand years for the formation of a thin layer of soil.
Since soil is made up of such diverse materials like broken down rock particles and organic material, it can be classified into various types, though based on the size of the particles it contains.
Soil Types
Depending on the size of the particles in the soil, it can be classified into these following types:
- Sandy soil
- This type has the biggest particles and the size of the particles does determine the degree of aeration and drainage that the soil allows.
It is granular and consists of rock and mineral particles that are very small.
Therefore the texture is gritty and sandy soil is formed by the disintegration and weathering of rocks such as limestone, granite, quartz and shale.
- Silty soil
- Silty soil is composed of minerals like Quartz and fine organic particles.
- Clay soil
- Clay is a kind of material that occurs naturally and consists of very fine grained material with very little air spaces, the drainage in this soil
is low, most of the time there is a chance of water logging.
Clay soil becomes very heavy when wet.
Clay soil is formed after years of rock disintegration and weathering. It is also formed as sedimentary deposits after the rock is weathered,
eroded and transported.
- Loamy Soil
- This soil consists of sand, silt and clay to some extent. The texture is gritty and
retains water very easily, yet the drainage is well. There are various kinds of loamy soil ranging from fertile to very muddy and thick sod.
- Peaty Soil (aka, Muck)
- This kind of soil is basically formed by the accumulation of dead and decayed organic matter. It naturally contains much more organic
matter than most of the soils. It is generally found in marshy areas. This kind of soil is formed in wet climate.
Peaty soil is prone to water logging.
- Chalky Soil
- Unlike Peaty soil, Chalky soil consists of a large number of stones. This kind of soil is prone to dryness.
In geotechnical engineering, bearing capacity is the capacity of soil to support the loads applied to the ground.
The bearing capacity of soil
is the maximum average contact pressure between the foundation and the soil which should not produce shear failure in the soil.
There are three modes of failure that limit bearing capacity: general shear failure, local shear failure, and punching shear failure.
Spread footings and mat (pad) foundations are generally classified as shallow foundations.
These foundations distribute the loads from the superstructures to the soil on which they are resting.
Failure of a shallow foundation may occur in two ways:
- by shear failure of the soil supporting the foundation
- by excessive settlement of the soil supporting the foundation
The first type of failure is generally called bearing capacity failure.
The general shear failure case is the one normally analyzed.
Prevention against other failure modes is accounted for implicitly in
settlement calculations.
There are many different methods for computing when this failure will occur. This is usually performed by a Soils Testing Laboratory.
As part of the information provided are the acceptable Footings Sizes and Loads, and Retaining Walls per the Florida Building Code.
Depending on you location, you may review the Building Code in your area, which may or may not contain similar information.
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