Building Foundations
Foundation Walls
Footings
 A base
 Monolithic
construction
 Independent
construction
Foundation-Wall Footings
 Spread footings
 Undisturbed soil
Footing Design
 Prevent settling or
cracks
 Minimum of 12” below
grade. Below frost line
 Thickness = thickness
of foundation wall
 Width = 2x thickness of
foundation wall
Footing Reinforcement
 Rebar embedded
2
lengths of ½”
diameter (#4)
rebar
 Positioned
minimum of 3”
above bottom
Footing Forms
 Form
 steel, lumber, or
combination of
lumber &
plywood.
 Keyway
Other Types of Footings
 Pier and post
 Stepped
Footings
Footing Drains
 4” diameter pipes at
base of footing
 Carries water away
from house.
 Sloped at least 1/8” per
foot
 Landscaping Fabric
Poured-Concrete Foundation
Walls
 Durable & water





resistant
Most building sites
Support any type of
house
8 –10” thick
Min. compressive
strength 2500 psi
Most 8’ high
Full Height Walls
 Formwork
 Reusable forms
 Wales
Standard Wall Forms
 Wood or metal
 Built on site
 Prefabricated
forms
 Snap-ties
 3 –7 days
Insulating Wall Forms
 ICFs (Insulating
Concrete Forms)
 Permanent
 Basic
components
 planks,
sheets, or
hollow blocks
 Standard wall
 Grid wall
Placement
 Poured continuously




without interruption
Cold joint
Water content
Remove Air pockets
Concrete vibrator
(stinger)
Crawl-space Walls
 Advantage –
reduced cost
 Soil cover
 Ventilated
 Insulated
 Piers support
Reinforcing Concrete Walls
 Rebar centered in
wall
 Lintel
Sill Plate Anchors
 Anchor bolts
 Metal strap
anchors
 Sill sealer
Foundation Wall Details
 Special
features:
 Brick-veneer
siding
 Utility Sleeves
Foundation Vents And
Windows
 Metal vents
 Rust-resistant
steel frame
windows
 Wood framing
(pressure treated)
Beam Pockets
 Girder flush with
top of sill plate
Stripping and Maintaining
Forms
 Wood wedges (no
metal pry bars)
 Stiff bristle (not
wire) brush
 Form-release
agent – Bio-slick
Moisture Protection
 Bituminous (tar)
coating
 Top of footings to
finished grade
level
Backfilling
 Filling in
excavation area
 Too soon, push in
foundation walls
 First floor framing
 Temporary
bracing
Concrete Block Walls
 Popular for
foundation walls
 No formwork
 Blocks
inexpensive
 Work stopped
and started
Concrete Block Basics
 Concrete Masonry





Unit (CMU)
Head Joint
Bed Joint
Common bond
Pilasters
Protect from
freezing & moisture
Cutting Block
 Brick hammer
and chisel
 Portable masonry
saw
Mortar
 Mortar bond
strength depends
on:






Type & quantity
Workability, or
plasticity
Surface texture
bedding areas
Rate at which
masonry units
absorb moisture from
mortar
Water retention
Skill of person laying
block
Mortar Mixtures
 Portland cement,
hydrated lime, sand,
& water.
 Prepackaged mortar
mix




Type N
Type M
Type S
Type O
Mixing and Placing Mortar
 Evaporation
 Hydration
 2 ½ hour when air
temp is 80ºF or
higher
 3 ½ hours when air
temp is below 80ºF.
Laying Block Foundation
Walls
 Skilled masons
 Corners built first
 Story pole
(course pole)
Intersections
 Control joint
Tooling the Joints
 Weather tight
joints & neat
block walls
 “Thumbprint hard”
 Tooling compacts
 Head joints, then
bed joints
Completing the Walls
 Hollow block
walls capped
 Strengthened with
rebar
Moisture Protection
 Damp proofed
or waterproofed
 Parging
Radon
 Colorless &
odorless
radioactive gas
 Extremely toxic
 Lung cancer
 Soluble in water
 9X heavier than
air
Radon-Resistant Construction
 Gas-permeable
layer
 Soil-gas retarder
 Sealants
 Vent pipe
 Cap course
Review
1.
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3.
4.
5.
6.
7.
What is the minimum depth required for an
exterior-wall footing?
Describe the type and position of reinforcement
that is commonly added to strengthen a footing.
What is a keyway and how is it formed?
For nearly all poured-concrete foundation walls,
formwork must be constructed for each wall face.
What holds the formwork together?
What creates a cold joint?
Why are the joints in a concrete block wall
tooled?
When using mortar, why is it helpful to know the
differences between hydration and evaporation?