Introduction to Foundations
What is a Foundation?
A Foundation is the structural support
for a structure.
Foundation materials include concrete,
brick, concrete block, and wood.
Foundation types and depths vary greatly
depending on the region of the country
that they are installed in.
Site Preparation
Before a foundation can be installed
the site has to be made ready.
The contractor responsible for this is
known as an excavator
The first step is typically to remove the
topsoil and to place it in a pile
This material is used to grade the site once
the house is completed
Excavation
What is Excavation
Excavation is simply to dig the hole for the
house
They dig a hole in the soil using a piece of
machinery known as a Front End Loader
How do they know how big the hole should
be?
Site Plans
The Site Plan is a drawing that is
generated by a Surveyor
The surveyor uses special instruments to
measure the Lot that the home is being
built on
They then work with the Architect to place
the home in the desired location on the
Plot Plan (Also called a Plot of Survey)
More on Site Plans Later
Frost Line
The Frost Line is the depth to which the
soil freezes on average during the
winter
Frost Line is measured in Inches
Depth of Frost Line varies depending on
the location of the jobsite
See chart
Frost Line
Foundation Heave
In cold climates the water in the soil
freezes during the winter.
Water expands as it freezes
This expansion can cause foundations that
are not below the frost line to move in an
upwards direction
This is known as Heave
In order to avoid heave Foundations must
be poured at a depth below the frost line
Frost Line & Foundation Depth
The depth of the Foundation is
proportional the Frost Line for the area
Foundations must be excavated to a depth
of at least 6” below the Maximum Frost
Line for the area
This is a general guideline and can be
overridden by local Building Codes
Foundation Footings
A Footing (Footer) is the bottom most
structural member of the foundation
Its job is to disperse the weight of the
home over a larger area of soil
This is the same principal as laying down
on thin ice to spread out your body weight
Footer size is determined by the width of
the Foundation Wall
Foundation Footings
Foundation Footings
Footer Form
Footer Form
Footer Form
Footer Form
Footer Form
Foundation Types
There are two main types of foundations
typically used in the Midwest
Slab on Grade is a Concrete Pad that is
poured at the same level as the surrounding
soil
Basement/ Crawl Space are poured deeper
than the level of the surrounding soil, leaving
a void under the structure of the home
Regardless of the type all Foundations
require a Footer
Slab on Grade
Slab Foundations are typical in areas
where the soil is to wet, or rocky for a
Basement to be practical.
Areas such as Florida do not have
basements, why?
Areas such as Arizona do not have
basements, why?
Slab on Grade
Slab Foundations are used in the
Midwest for things such as:
Garage floors
Porches
Sheds
Homes where a basement is not desired
Slab on Grade
Slab on Grade
Slab Foundations are made with
Poured Concrete and Reinforced using
Steel Rod or Rebar
Typically 4-6” Thick
Home Floors are level
Garage floors are pitched away from the
home to ensure proper drainage
Crawl Space Foundation
A Crawls Space Foundation is built in a
similar fashion to that of a Basement
Foundation, the only difference is the
height
While Basements are tall enough for
people to walk in, Crawl Spaces are only
tall enough for people to crawl in
Typical height for a Crawl Space is 18” –
36”, with 18” being the minimum
Crawl Space
Basement Foundation
A Basement Foundation is dug deep
enough for people to walk in
They are typically 8’ – 9’ deep, with some
going as deep as 10’
The main advantage of a Basement
Foundation is that it can be used as living
space
The cost is considerably less than the
price of the first floor
Basement Foundation
Basement Cost Vs Crawl Space
Both Require same labor to layout
Both Require same machinery to Excavate
Basement is deeper which means:
Slightly more Labor
Slightly more Concrete
Slightly more extra materials
In the end if possible Basements are the
way to go!
Basement Advantages/ Uses
Basements house all of the
Mechanicals, such as the Furnace,
Electrical Panel, and Hot water Heater
Basements have many uses:
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Storage
Workshop
Kids play room
Home Theatre
Others?
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Rec Room
Living Area
Office Space
In Law Quarters
Foundation Walls
Foundation Walls are what support the
Home
They are built on top of the Footer
There are several types of Foundation
Walls
CMU (Cinder Block)
Wood
Poured Concrete
Rock/ Stone (When?)
CMU Foundation Walls
Concrete Masonry Unit (CMU) or Cinder
Block Walls are placed by hand
Requires more labor
Each CMU must be laid by a trained
Mason
CMU’s are held together using Mortar
Use a Poured Concrete Footer
Labor makes them less Cost Effective than
Poured Walls
Wood Foundation Walls
Wood Foundation Walls are built of
Pressure Treated wood
This material is resistant to Rot, Insects
and Decay
Use 2x4 or 2x6 lumber
Faced with special plywood
Insulated with Fiberglass Wool
Typically uses a wood Footer
Polyethylene Film used as a Vapor Barrier
Poured Concrete Walls
Most common type of Foundation Wall
in the Midwest
Forms are erected to our the Concrete
into
Forms are built from Wood and are tied
together using Steel Rods (Holds Spacing)
Concrete is delivered to the site in a
Ready Mix Delivery Truck
It is then Poured into the forms using
either a Chute or a Boom (Pumper Truck)
Concrete Truck w/ Chute
Concrete Truck Oops
Concrete Truck w/ Pumper
Concrete Truck w/ Pumper
Poured Concrete Walls (cnt’d)
Very fast and Cost Effective method of
building a Foundation
Typical time from Footer to Walls can be
as little as Three Days
Very strong, Concrete has a very high
Compression Strength
Rock/ Stone Walls
Before concrete became a readily
available building material Stones and
Rocks were used to create foundation
walls
Stones were gathered from surrounding
fields
They were held in place using mortar
Basements weren’t typically used as living
space (root/ storm cellar)
Not used in modern home construction
Foundations & Drainage
Water must be drained away from the
house
This is done using a system called a Drain
Tile
A 4” Perforated Corrugated plastic drain
pipe is placed as the base of the footer
18” of course (1”) Gravel is then filled in on
top of the Drain Pipe
The Gravel prevents smaller material from
entering the pipe, this would cause the pipe
to clog
Foundations & Drainage (cnt’d)
The Drain Pipe is then typically connected to
a Sump Pump
A Sump Pump is a Submersible Electric
Water Pump that is placed in a Sump Well
Water enters the Sump Well and when the
level reaches a preset height a Float turns
the Sump Pump on
Water is then pumped out of the Sump Well
to either the City Sewer connection, or to a
location at Grade Level outside of the home
Drain
Tile
Damp Proofing Foundations
Poured Concrete and CMU Foundation
Walls must be protected from water
This is because they are made of a Porous
material, and without proper Damp Proofing
water could seep into the basement
There are Three typical methods of Damp
Proofing
Sprayed Hot Tar or Rubber Membrane are
sprayed from a tank in an enclosed truck
through a Spray Gun that is similar to a
Pressure Washer
Damp Proofing (cnt’d)
Commercial Cement Paint may be applied,
this is either sprayed or rolled on
Parge Coat, this method involves spreading
plaster over the entire Footer and
Foundation Wall
There must be two layers applied
Thickness must be 1/4” minimum
Sprayed Hot Tar is the most common
method of Damp Proofing, as it is the fastest
and most Cost Effective of the three
Concrete Basement Floors
Once the Concrete Walls have Cured and
the forms have been removed the Basement
Floor can be poured
A layer of Compacted Sand or Gravel is
placed inside the foundation walls
Typical Depth is 4”-6”
A 1” Layer of Sand is placed on the inside
top of the Footer, this acts as a barrier to
prevent the Floor and the Footer from
Bonding
Concrete Basement Floors
Plumbing Rough Ins are made in the floor if
you plan to have a bathroom in your
basement. These include the drain for the
toilet and the shower/ bath
There is also a drain in the floor that allows
the condensation from the air conditioner to
be removed. This needs to be placed by the
Mechanical Area
Depending on the height of the City Sewer
Connection the Sewer Main is roughed in
through the floor, or the wall
Concrete Basement Floors
A 6mm Polyethylene Vapor Barrier is then
placed on top of the sand
A screen board is fastened to the perimeter
walls, this ensures that the Finished Floor will
have an even depth
Lastly Concrete is poured into the basement
in the same fashion as the Foundation Walls
The Concrete is smoothed out using a tool
called a Float.
Concrete Basement Floors
Basement Heights
Caution must be used when describing the
height of the basement ceilings.
Ceiling height is measured from the finished
Concrete floor to the Ceiling Joists above
EX. If you say that you have 8’ ceilings the
clear dimension will be less than 8’ WHY?
If you want to tell the client that they are
getting a ceiling in their basement that is a
true 9’ you must compensate for this,
WHERE?
I-Beams & Columns
The weight of the house is supported by the
Foundation Walls, and the Footer
This weight is comprised of the Walls,
Floors, Roof, and Contents of the Home
However… The building materials that are
used to span the First Floor of the home
(Called Floor Joists) are made of wood and
can only span a certain distance
If the span is greater than the Rating of the
Floor Joist Support Columns and Steel/
Engineered Beams must be used
I-Beams & Columns (cnt’d)
A Steel Beam is used in a perpendicular
direction to that of the Floor Joists
The Beam sits on top of the Foundation
Walls or in a Beam Pocket
The Floor Joists then sit on the Top of the
Beam, the span is effectively cut in half
The catch is that the Beams only have a
certain distance that they can span. When
this distance is reached Lally Columns must
be used to periodically support the Beam
I-Beams & Columns (cnt’d)
I-Beams & Columns (cnt’d)
I-Beams & Columns (cnt’d)
I-Beams & Columns (cnt’d)
I-Beams & Columns (cnt’d)
There are two main types of Support Beams
Steel Beams they are commonly known as
I-Beams due to their shape
The two most common types are S and W
beams, they both have an I shape but..
S Beams have Narrow Flanges
W Beams have Wide Flanges
S & W Steel Beams
I-Beams & Columns (cnt’d)
The other type of Support Beam is a Wood
Laminate beam
The are commonly called Glue Lam or LVL
It is composed of multiple pieces of wood
that are glued together using heat and
pressure
LVL beams have span and strength
characteristics similar to those of steel
Example
Lally Columns
Lally Columns are made of steel
The Diameter of the Lally Column is
determined by the Load that must be supported
Lally Columns can be a single column, or they
can be paired together, again this is determined
by the load that is supported
Flanges are welded to the top and bottom of
the Lally Column, the top is the width of the
Support Beam, with bolting holes to bolt it to
the Beam
The bottom Flange is covered by the Basement
Floor
Lally Column Footers
Since Lally Columns support large amounts of
weight they require a special footer
This footer is also Square Poured Concrete
Footer sizes are as follows:
One Story: 8” Deep and 5” larger on each
side of the column
Two Story: 12” Deep and7” larger on each
side of the column
Lally Column
Footers
Load Types
House Loads are split into two types:
Live Load: Fixed or moving objects
People, Furniture, Snow/ Rain on the
Roof & Wind
Dead Load: Fixed or Static Weights
Walls, Roof, Foundation, Floors, Siding
and Joists
Load Sizing
House Loads are estimated using the
following calculations:
Area of House in Sq Ft = W X L (In Feet)
Weight of each floor = 50#/Sq Ft
Weight of the Ceiling = 30#/Sq Ft
Weight of Roof = 0 (Supported by Walls)
Weight of Load Bearing Walls 10#/Sq Ft
Concrete
What is Concrete?
Concrete
What is Concrete?
Concrete is a mixture of Four key ingredients:
Cement
A Binding Agent for the Aggregate and Sand
Made from Limestone and Clay or Sand
Heated in a Kiln to 2700°F
Water
Aggregate
Gravel
Sand
Concrete
Concrete Cures via Chemical Reaction
When Concrete Cures it generates Heat
Final product can be described as a rock like
substance
Steel Reinforcing bar or Rebar is added to give it
strength
Concrete has very high Compression Strength,
but low in Tension Strength
Tension Strength is a pushing or pulling force
Rebar strengthens the wall laterally