Weekend Cabin Retreat Project
Foundations and Foundation Plans
Sacramento City College
EDT 300
EDT 300 - Foundation Plan Design
1
Objectives
 Describe
the procedure for staking
out a house location.
 List
the major considerations when
designing a footing for a residential
foundation.
 Analyze
a typical floor plan to
determine the appropriate
foundation.
2
EDT 300 - Foundation Plan
Design
Masonry Foundation
3
EDT 300 - Foundation Plan
Design
Wood Foundation
4
EDT 300 - Foundation Plan
Design
Staking Out House Location
 The
plot plan provides the necessary
dimensions required for staking out
the location of the house on the lot.
 Tools for staking out:
 Measuring
tape
 Contractor's level
 Transit (if required)
5
EDT 300 - Foundation Plan
Design
Staking Out House Location
 First
Step
 locate
each corner by laying off the
distances indicated on the plot plan.
 Drive a stake into the ground at the
location of each corner of the foundation to
identify its position.
6
EDT 300 - Foundation Plan
Design
Staking Out House Location
7
EDT 300 - Foundation Plan
Design
Staking Out House Location
 Square
corners may be laid out using
the 9-12-15 unit method.
 These proportions define a right
triangle and establish a 90 angle
corner.
8
EDT 300 - Foundation Plan
Design
Staking Out House Location
9
EDT 300 - Foundation Plan
Design
Staking Out House Location
 Batter
boards are used to retain the
location of the foundation during
excavation and construction.
 Are
constructed of 2 x 4 stakes driven into
the ground about 4 feet outside the footing
line.
 A 1 x 6 board is nailed horizontally to the
stakes so all are level and in the same
horizontal plane. (They will have the same
elevation.)
10
EDT 300 - Foundation Plan
Design
Staking Out House Location
11
EDT 300 - Foundation Plan
Design
Staking Out House Location
 A strong
cord is stretched across the
boards at opposite ends of the building and
located directly above the corner stakes.
 A plumb bob is used for accurate
placement of each stake.
 This is done for each side of the building.
 A saw kerf (cut) is usually made at the
exact point on the horizontal batter board
where the string is located.
 This prevents movement of the string along
the board.
12
EDT 300 - Foundation Plan
Design
Staking Out House Location
 After
cuts are made in all eight
batter boards, the outlines of the
house will be located.
 A control point is needed to
determine the depth of excavation
and foundation wall height.
 The corner with the highest elevation
is usually selected for this purpose.
 The finished floor should be at least
8 inches above the grade.
13
EDT 300 - Foundation Plan
Design
Excavation
 In
excavating for footings and
foundation walls, the top soil is
usually removed using a bulldozer or
tractor with a blade.
 This soil is saved for final grading.
 A trencher or backhoe may be used
to excavate for foundations when
either slab construction or a crawl
space is planned.
14
EDT 300 - Foundation Plan
Design
Excavation
 In
excavating for a basement, a
backhoe used.
 Selection of excavating equipment is
determined by the size of the
excavation and type of soil.
 Excavation for footings should
extend down to a minimum of 6 in.
into undisturbed earth.
15
EDT 300 - Foundation Plan
Design
Excavation
 It
must also be at least 6 in. below
the average maximum frost
penetration depth.
 Local codes usually specify the
minimum footing depth for a given
area.
16
EDT 300 - Foundation Plan
Design
Excavation
17
EDT 300 - Foundation Plan
Design
Excavation
 No
backfilling should be permitted
under the proposed footings, because
uneven settling of the house may
occur.
 Footings on rock. About 6 in. of the
rock should be removed under the
proposed footing and replaced with
compacted sand to equalize settling.
18
EDT 300 - Foundation Plan
Design
Excavation
 Sites
which have recently been filled
and regraded: the footings should
extend down to the original
undisturbed earth.
 Unless
soil tests prove that the earth is
sufficiently compacted to properly support
the structure.
19
EDT 300 - Foundation Plan
Design
Excavation
 Excavation
must be large enough to
allow space to work when constructing
the foundation wall and laying drain
tile.
 The steepness of the back slope will
depend on the type of soil
encountered.
 Sandy
soil is likely to cave-in and,requires
a gentle back slope.
 Clay may be nearly vertical.
20
EDT 300 - Foundation Plan
Design
Footing Shapes
 Footings
increase the supporting
capacity of the foundation wall by
spreading the load over a larger area.
21
EDT 300 - Foundation Plan
Design
Footing Shapes
 If
a foundation was built on rock, a
footing would not be necessary.
 Most houses are not built on such
solid material and therefore need
footings to support the heavy loads.
 The size and type of footing should
be
 suitable
for the weight of the building and
 soil bearing capacity.
22
EDT 300 - Foundation Plan
Design
Footing Shapes
 Footings
for most residential
structures are made of poured
concrete.
 The size of footing required is
commonly determined by using the
foundation wall thickness as a basis
for its proportions.
23
EDT 300 - Foundation Plan
Design
Footing Shapes
24
EDT 300 - Foundation Plan
Design
Footing Shapes
 This
size footing is designed for most
normal soil conditions ranging from
sand to clay.
25
EDT 300 - Foundation Plan
Design
Footing Shapes
 Foundation
walls should be centered
along the footing.
 The footing will project beyond each
side of the foundation wall a distance
equal to one-half the thickness of the
foundation wall.
 If the soil load bearing capacity is
very poor, the size of footings should
be increased and reinforced with
steel.
26
EDT 300 - Foundation Plan
Design
Footing Shapes
 The
footings must be large enough to
minimize the effects of:
 settlement
of the structure.
 unequal compressibility of the soil.
 to
reduce cracking.
 The weight of most homes is greater
on two of the four walls which causes
unequal loading.
27
EDT 300 - Foundation Plan
Design
Footing Shapes
28
EDT 300 - Foundation Plan
Design
Foundation Walls
 Foundation
walls extend from the
first floor to the footing.
 A foundation wall may also be a
basement wall.
29
EDT 300 - Foundation Plan
Design
Foundation Walls
 Materials
used to build foundation
walls include
 cast
(poured) concrete
 concrete block
 pressure-treated wood
 stone or brick in rare instances
30
EDT 300 - Foundation Plan
Design
Foundation Walls
 Cast
concrete and concrete block are
widely used in residential structures.
 Pressure-treated wood foundations
are gaining acceptance for residential
structures.
 Brick is much more expensive than
cast concrete, block, or wood, and is
seldom used.
 Stone was once used extensively, but
is no longer of significance as a
foundation material.
31
EDT 300 - Foundation Plan
Design
Footing Materials
32
EDT 300 - Foundation Plan
Design
Footing Materials
33
EDT 300 - Foundation Plan
Design
Footing Materials
34
EDT 300 - Foundation Plan
Design
Foundation Walls
 Foundation
types:
walls are of four basic
 T-foundation
 slab
foundation
 pier or post foundation
 permanent wood foundation
35
EDT 300 - Foundation Plan
Design
Foundation Types
36
EDT 300 - Foundation Plan
Design
Foundation Types
37
EDT 300 - Foundation Plan
Design
Foundation Walls
 The
type chosen for a particular
situation will depend upon
 the
weight to be supported
 load bearing capacity of the soil
 location of the foundation in the building
 climate
 local codes
 preferred building practice.
 All
should be considered when
designing a foundation.
38
EDT 300 - Foundation Plan
Design
T-Foundations
 Most
common foundation type
 Looks like an inverted T.
 The foundation and footing are
usually two separate parts but may be
cast as a single unit.
39
EDT 300 - Foundation Plan
Design
T-Foundations
 Concrete
for footings of a Tfoundation is usually placed in forms
made from construction lumber.
 The form boards are nailed to stakes
once they are level.
 Stakes prevent movement while the
concrete is being cast.
40
EDT 300 - Foundation Plan
Design
T-Foundations
41
EDT 300 - Foundation Plan
Design
Slab Foundations
A
slab foundation is an extension of a
slab floor.
 It is placed at the same time the
floor is cast and is not a separate
unit.
 It is sometimes called a thickened
edge slab.
42
EDT 300 - Foundation Plan
Design
Slab Foundations
 The
foundation wall should extend
down below the frost line, as in the
case of the T-foundation.
 Use of steel reinforcing bars or mesh
is recommended for the slab
foundation to prevent cracking due to
settling.
43
EDT 300 - Foundation Plan
Design
Slab Foundations
 Some
of the primary advantages of
the slab foundation
 requires
less time, expense, and labor to
construct.
 no separate footing is required, excavation
is not as extensive as for the T-foundation.
 Less time is required since the entire
foundation and floor is placed in one
operation.
44
EDT 300 - Foundation Plan
Design
Pier and Post Foundations
 Many
situations in residential
construction lend themselves to the
use of piers, columns and posts.
 Cheaper and just as satisfactory to
use piers rather than the Tfoundation under parts of the
building.
 Example:
a crawl space is planned and the
distance is too great for a single span, the
pier foundation is a logical choice,
45
EDT 300 - Foundation Plan
Design
46
EDT 300 - Foundation Plan
Design
Pier and Post Foundations
 Another
common application: a
basement or garage where the
distance is too great to span with
floor joists.
 Lally
columns are used to support a beam
that in turn supports the joist., rather than
construct a bearing wall partition.
47
EDT 300 - Foundation Plan
Design
48
EDT 300 - Foundation Plan
Design
Pier and Post Foundations
 Basic
difference between a pier and
column is the length.
 Piers are usually much shorter and
ordinarily located under the house.
49
EDT 300 - Foundation Plan
Design
Pier and Post Foundations
50
EDT 300 - Foundation Plan
Design
Pier and Post Foundations
51
EDT 300 - Foundation Plan
Design
Pier and Post Foundations
 The
column is composed of two
pieces; a footing and post.
52
EDT 300 - Foundation Plan
Design
Pier and Post Foundations
 The
footing is usually square or
rectangular
 The post may be masonry, steel, or
pressure-treated wood.
53
EDT 300 - Foundation Plan
Design
54
EDT 300 - Foundation Plan
Design
Wood Foundations
 Wood
foundations are known by
several names:
 the
permanent wood foundation (PWF)
 the all-weather wood foundation (AWWF)
 the treated wood foundation.
55
EDT 300 - Foundation Plan
Design
Wood Foundations
A
wood foundation is a below grade
pressure-treated plywood-sheathed
stud wall.
 The wood foundation is attractive in
climates where typical (concrete and
masonry) foundation work stops in
freezing or rainy weather.
56
EDT 300 - Foundation Plan
Design
Wood Foundations
 All
wood parts are pressure-treated
with chemical solutions that make the
wood fibers useless as food for
insects or fungus growth.
57
EDT 300 - Foundation Plan
Design
Wood Foundations
 The
system is accepted by
 the
Federal Housing Administration (FHA)
 the Department of Housing and Urban
Development (HUD),
 Farmers Home Administration (FmHA)
 the major model building codes
 It is rapidly gaining acceptance in state and
local codes as well.
58
EDT 300 - Foundation Plan
Design
Wood Foundations
 The
system may be used in full
basement or crawl space construction
 It is adaptable to most any site and
light-frame building design.
59
EDT 300 - Foundation Plan
Design
Wood Foundations
60
EDT 300 - Foundation Plan
Design
Wood Foundations
 Crawl
spaces
 A trench
is excavated to receive the footing
and foundation wall.
 The trench should be at least 12 in. deep
regardless of the frost depth.
 The depth of the excavation should be
below the average maximum frost
penetration depth.
 2 in. of sand or 6 in. of crushed stone or
gravel are raked smooth in the bottom of
the trench.
 This provides a level base for the footing.
61
EDT 300 - Foundation Plan
Design
Wood Foundations
 The
footing is generally 12” wide.
 Local
62
codes may require wider footings.
EDT 300 - Foundation Plan
Design
Beams and Girders
 Most
residences have spans too great
to use unsupported floor joists.
 A beam or girder is required to
support the joists and prevent
excessive sagging.
 The beam is usually placed an equal
distance from each outside wall or
under a bearing wall.
 A bearing wall is designed to support
part of the load of the structure.
63
EDT 300 - Foundation Plan
Design
Beams and Girders
 Beams
may be either wood or metal.
 Wood beams are of two types builtup and solid.
 Built-up beams
 are
used more frequently
 easier to handle
 more readily available
 do not check to the extent of solid beams.
 However,
solid beams are generally
stronger and more fire-resistant.
64
EDT 300 - Foundation Plan
Design
Beams and Girders
 Two
types of steel beams are
commonly used: S-beams and wideflange beams,
65
EDT 300 - Foundation Plan
Design
Beams and Girders
 The
wide-flange beam
 will
support greater weight
 is more stable than the standard S beam
 it is more popular for residential
construction.
66
EDT 300 - Foundation Plan
Design
Beams and Girders
 Calculation
of the size beam needed
is based on the weight of the
structure.
 Weights are designated either as live
loads or dead loads.
67
EDT 300 - Foundation Plan
Design
Beams and Girders
 Live
loads are those fixed or moving
weights, which are not a structural
part of the house.
 Examples include:
 furniture
 occupants
 snow
on the roof
 wind, etc.
68
EDT 300 - Foundation Plan
Design
Beams and Girders
 Dead
loads are those static or fixed
weights of the structure itself.
 Examples of dead loads are the
weights of:
 roofing
 foundation
walls
 siding
 joists,
69
etc.
EDT 300 - Foundation Plan
Design
70
EDT 300 - Foundation Plan
Design
71
EDT 300 - Foundation Plan
Design
Building Structure Loads
 First/Second
Floor
 Live
load plus dead load = 50 pounds per
square foot.
 Ceiling
 Live
load plus dead load = 30 pounds per
square foot.
 Walls
 Dead
 Roof
load = 10 pounds per square foot.
 No
load on the beam. Exterior walls
generally support the roof.
72
EDT 300 - Foundation Plan
Design
Building Structure Loads
 Weight
Calculations
 The example used is for a two-story
frame structure which is
28'-O" x 40'-O".
 Width
x length = Area of the house.
 28' x 40' = 1120 sq. ft. for each floor.
 8' x 40' = 320 sq. ft. of wall area for each
wall.
73
EDT 300 - Foundation Plan
Design
Building Structure Loads
 Weight
per sq. ft. x number of sq. ft.
= total wt.
 Weight
of first floor
 (1120 sq. ft. x 50 lbs./sq. ft.) = 56,000 lbs.
 Weight of second floor
 (1120 sq. ft. x 50 lbs./sq. ft.) = 56,000 lbs.
 Weight of ceiling
 (1120 sq. ft. x 30 lbs./sq. ft.) = 33,600 lbs.
 Weight of roof on beam
 (none in this example)
0 lbs.
 Total
145,600 lbs.
74
EDT 300 - Foundation Plan
Design
Building Structure Loads
 One-half
of the total weight bears
on the center beam.
 (1/2
x 145,600 pounds)
 Weight of first floor wall
 (320 sq. ft. x 10 lbs./sq. ft.)
 Weight of second floor wall
 (320 sq. ft. x 10 lbs./sq. ft.)
 Weight bearing on beam
 One
75
“kip” is 1,000 pounds
EDT 300 - Foundation Plan
Design
= 72,800 lbs.
= 3,200 lbs.
= 3,200 lbs.
= 79,200 lbs.
Building Structure Loads
76
EDT 300 - Foundation Plan
Design
Building Structure Loads
77
EDT 300 - Foundation Plan
Design
Building Structure Loads
78
EDT 300 - Foundation Plan
Design
Building Structure Loads
79
EDT 300 - Foundation Plan
Design
Lintels
A
lintel is a horizontal structural
member that supports the load over
an opening such as a door or window.
 Lintels may be constructed of
 precast
concrete
 cast-in-place concrete
 lintel blocks
 steel angle.
80
EDT 300 - Foundation Plan
Design
Lintels
 When
lintels are used in a masonry
wall, the ends must extend at least 4
in. into the wall on either side of the
opening.
 Common precast lintel sizes for
residential construction are 4" x 8",
4" x 6", and 8" x 8".
81
EDT 300 - Foundation Plan
Design
Lintels
82
EDT 300 - Foundation Plan
Design
Lintels
83
EDT 300 - Foundation Plan
Design
Lintels
84
EDT 300 - Foundation Plan
Design
Lintels
 Lintels
are also made of angle steel.
 They are available as equal angles
(both legs the same size) or as
unequal angles.
85
EDT 300 - Foundation Plan
Design
Lintels
86
EDT 300 - Foundation Plan
Design
Lintels
 Openings
in cast concrete walls do not
require lintels.
87
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 Concrete
is the result of combining
cement, sand, aggregate (usually
stone or gravel), and water.
 Cement is composed of a mixture of
lime, silica, alumina, iron components,
and gypsum.
 The proportions of the ingredients
will vary with the requirements.
88
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 Sidewalks,
driveways, footings, and
basement floors usually contain one
part cement, three parts sand, and
five parts aggregate.
 Footings as well as concrete floors
must have both a minimum
compressive strength of 3,000 psi
and minimum cement content of 5
bags (470 lbs.) per cubic yard.
89
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 The
amount of water used will most
likely be 6 or 7 gallons for each bag
of cement (normally 94 pounds per
bag).
 Concrete cures over a long period of
time and should be kept moist for
several days after it is placed.
 Failure to do this reduces strength
and may harm the exposed surface.
90
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 Temperature
also affects the setting
time of concrete.
 Cold weather slows down the process
and concrete should not be allowed to
freeze before it has set.
91
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 Concrete
is ordered by the cubic yard
(27 cubic foot).
 The consistency is generally specified
by how many bags of cement are
contained in each yard of mix.
 A "five-bag mix" is considered
minimum for most jobs.
 A "six-bag mix" will produce a
stronger product and should be used
when high strength or reinforcing is
required.
92
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 When
concrete is being placed, it
commonly traps air pockets within the
mixture.
 These air pockets are worked out by
vibrating or tamping.
 This action helps to form a more
dense material and removes weak
spots due to air pockets.
93
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 After
the concrete has been placed, a
screed is used to smooth the surface.
 The screed is a long straightedge,
usually a board, which is worked back
and forth across the surface.
 This
action brings excess water to the
surface and settles the aggregate.
 Power
screeds are a so available for
large jobs.
94
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 When
screeding is finished, the
surface is then worked over with a
float.
 A float is a short board about a foot
long with a handle attached to one of
the flat sides.
95
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 The
purpose of “floating” is:
 (1) to embed the large aggregate just
beneath the surface,
 (2) to remove any slight
imperfections, lumps, and voids to
produce a flat surface, and
 (3) to consolidate mortar at the
surface in preparation for final steeltroweling.
96
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 As
the mixture reaches the proper
consistency, the troweling process is
started.
 The trowel is rectangular and is used
in a circular motion.
 This troweling action further hardens
the surface and develops a very
smooth finish.
 A slightly rough surface is made by a
broom.
97
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 When
ordering concrete, one should
figure only 25 cubic feet to the yard.
 Some of the material will remain in
the mixer, some will be spilled, and
forms may sag.
 Experience has shown that it is
better to have a little more concrete
than you need than to have too little.
98
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 Large
areas of concrete crack from
expansion and contraction due to
changes in temperature and moisture
content.
 Cracking may be minimized or
controlled by contraction joints.
 Contraction joints should be placed in
line with interior columns, at changes
in the width of the slab, or at
maximum spacing of about 20 ft.
99
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 Joints
are formed by cutting grooves
in the freshly placed concrete with a
jointing tool.
 They can be cut into the slab with a
power saw after the concrete has
hardened.
 The depth of joints or grooves should
be one-fourth the thickness of the
slab.
100
EDT 300 - Foundation Plan
Design
Concrete and Masonry
A
concrete slab is usually placed
directly on firmly compacted sand 4
to 6 inches thick.
 Dry sand should be dampened to
prevent absorption of too much
mixing water from the fresh
concrete.
101
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 The
sand should be
 thoroughly
compacted to prevent
settlement of the slab.
 sloped toward the floor drains to ensure a
uniform slab thickness.
 Floor
slabs usually have a minimum
thickness of 4 inches.
102
EDT 300 - Foundation Plan
Design
Concrete and Masonry
 Floor
slabs should not be bonded to
footings or interior columns.
 A sand cushion 1 in. thick may be used
to separate the slab from the
footing.
 A sleeve of three thicknesses of
building felt may be wrapped around
columns to break the bond.
103
EDT 300 - Foundation Plan
Design
104
EDT 300 - Foundation Plan
Design
Concrete Blocks
 Concrete
blocks are used extensively
in residential buildings for exterior
and interior walls.
 Concrete blocks are hollow concrete
masonry units, usually 8" x 8" x 16" in
dimension.
 The actual size is 7 5/8" x 7 5/8" x
15 5/8".
 These dimensions allow for a 3/8 in.
mortar joint.
105
EDT 300 - Foundation Plan
Design
Concrete Blocks
106
EDT 300 - Foundation Plan
Design
Concrete Blocks
107
EDT 300 - Foundation Plan
Design
Concrete Blocks
 The
distance from the center line of
one,mortar joint to the center line of
the next will be 8 or 16 inches.
108
EDT 300 - Foundation Plan
Design