Chapter 5
Light Wood Frame Construction
Light Wood Framing
Advantages
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Flexible
Easily constructed
Economical
Disadvantages
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Burns rapidly,
Decays if exposed to moisture
Changes volume with moisture changes
Framing unattractive (must be covered)
History - Prior to mid-1800s
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Timber Frame
timber with masonry
timber with earth fill
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Interior walls were simple plank structure
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Trees were plentiful, and labor was intense.
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Craftsmen were available, but tools were
limited – and had to be operated by hand.
History - mid 1800s
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Light wood framing advanced by
 Development of water powered saw mills
 Machine made nails became available
Earliest Version of Lt. Wood Framing
 Balloon Framing
Long lengths of material was plentiful
Wood members were small & easily handled
Provided for lateral stability
Balloon Framing
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Erection of wall framing members on a
wood sill secured to the foundation and
lapped against the floor joists.
Second floor joists lapped into the wall
framing system.
Roof framing then set on top of wall
plates. Roof rafters tied to ceiling joists
secured lateral displacement of exterior
walls.
Components were light in comparison
to timber structures, and erection
required minimal labor than before.
The practice was a more efficient use of
material.
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DISADVANTAGES OF BALOON FRAMING
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Long, straight lengths of material diminished in
availability as more structures were built.
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When buildings caught fire, the wall cavity of
balloon framing allowed fire & smoke to chimney
all the way to the roof, and structures burned
rapidly.
Since the wall and floor structure were built
integrally, most of the framing work was done off
the ground, where level conditions might not exist.
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PLATFORM FRAMING
With the disadvantages of balloon
framing, the platform frame system
evolved.
The floor structure was first built
onto the foundation sill, then
decked to provide a ‘platform’ on
which to work.
Ground-floor walls were erected
with a top plate to receive the
second floor joists, which became a
sill on which to erect the upper floor
joists – which, when decked became
another platform.
Single floor framing was more
plentiful because of shorter lengths.
wall
studs
wall
studs
sub floor
sub floor
floor
joists
floor
joists
sill
foundation
BALOON
sill
foundation
PLATFORM
studs and
joists are
lapped
wall
studs
single 2"x4"
plate
second
floor joists
temporary
ledger
BALOON
second
floor joists
wall
studs
2 - 2"x4"
plate
PLATFORM
roof
deck
rafters
ceiling joists
2 - 2"x4"
plate
fascia
wall
studs
Building Sequence
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Architect Plans and Designs the Facility – Then
Prepares Design and Construction Documents
Involve a selected Contractor, who:
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Obtains Building Permit
Purchases necessary materials
Selects Sub-Contractors for each phase of work
Excavation for utilities, foundations
Install Underground utility lines (electrical,
plumbing)
Foundation construction
Floor Construction
Erect Framing for Structure
Build construction pad & set batter boards
Batter boards enable accurate layout of foundation
A transit ensures accurate angles in layout
A level is used to ensure proper grades & elevation
Excavate & Place Foundations
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Materials Typically Used:
 Site Cast Concrete
 Concrete Masonry Units
 Reinforcing Steel
 Tie wire
 Anchor Bolts
Foundation and Basement Wall Construction
 Construction for support of loads
 Damp proofing and/or perimeter insulation
Foundation Wall Systems
Sill
Anchor
Dampproofing
Concrete or
CMU Wall
Gravel for
Drainage
Drainage Stone
under floor slab
with Vapor
Barrier
Perforated
Drainage
Pipe
Concrete
grade beam
Utility installation is simultaneous with foundation work
Installation of Plumbing Drainage Piping
Underground Plumbing
Example of grade beam monolithic with concrete floor
Wall
Load
Granular
Base
Thickened
Slab on
grade
Installation of plastic vapor barrier under concrete floor
Vapor
Barrier
Granular
SubBase
Foundation Insulation
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Some building codes require
perimeter insulation at
foundations – especially in
cold climates.
Insulate the Crawl Space or
Basement Walls
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Attach to Platform or on Ground
Vapor Barrier
Building the Platform Frame in Wood Floor With
Crawl Space
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Sequence of Assembly
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Install sills with insect barriers
Bolt sill members to the Foundation
Install floor framing and bridging
Install floor decking
Attachment to the Foundation
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Sill Material
 Treated for
resistance to insects
& decay in damp
climates.
Install insect shields
Sill Attachment with
anchor bolts
Floor Framing Options
FRAME WITH
DIMENSION LUMBER
FRAME FLOORS
USING TRUSSES
FRAME FLOORS WITH “I” JOISTS
Floor Framing
Spacing & Splicing
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Spacing
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Factors that determine joist spacing:
Floor Loading & Span Length
 Strength of Joist Material Used
 Type & thickness of floor decking
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Designation - Inches “o.c.” (on center)
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Typical - 12” , 16”, or 24” – to fit standard lumber
lengths)
Bridging for Floor Framing
Floor Framing
Using Steel Anchors
Decking over Floor Framing
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Materials Used
 Plywood or OSB
 Concrete or gypsum is poured over second
floor decks for sound deadening
Installation
 Deck is laid perpendicular to floor joists
 End joints are staggered to brace joists
 Power nails, screws, construction adhesive
Building Sequence for Ground Floor Walls
Layout
 Sole plates installed to define wall
locations
 Wall Framing - Lay out studs & assemble
with single top wall plate
 Tilt up walls on the Platform & fasten to
sole plate
 Install second layer of top wall plate to tie
all partitions and walls together.
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Install Wall Sheathing
 Corner bracing required for lateral stability
– usually OSB or plywood at all exterior
corners
Framing Terminology
Top Plate Doubled
Stud
Header
Sheathing
Decking
Sole Plate
Headers
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Headers are beams installed over
openings to carry weight of second floor
or roof loads.
Sizing Factors:
Load, Span, Material
Materials: dimension lumber, Laminated
wood, or Steel
Erecting the Wall Framing
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Build framing on the Platform & Tilt-up,
brace, and fasten to sole plates.
Double Top Plate
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Joist Support
Tie Framing
Together
Double Top
Plate
Header Supports
Double
Header
Corner
Framing
Sole Plate
Anchorage
Wall Sheathing
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Materials:
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OSB or Plywood for corner bracing
Insulating Sheathing - (no structural qualities)
Exterior Wall Sheathing:
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Joins & stabilizes the structure
Resists uplift
Resists racking & lateral forces
Provides surface for finish material
Building Sequence
PLATFORM & 2ND Story Walls
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Erect 2nd Story Platform
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Similar to 1st Floor Sequence
Install 2nd Floor access (stairs)
Erect 2nd Story Walls & Sheathing
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Similar to 1st Floor Sequence
Building Sequence
Attic Floor & Roof
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Options
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Build-in-place ceiling joists, rafters,
and bracing, OR
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Prefabricated Trusses, OR
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Combination
Roof Framing Built-in-Place
Ridge Board
Rafters
Collar Ties
LOOKOUTS
TO FORM
OVERHANGS
GABLE
FRAMING
Prefabricated Roof Trusses
Note Strand
Orientation
Hurricane
Clip
Metal clips in decking prevent uneven deflection
Roof Profiles
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Flat Roof
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Single Pitch
Roof Profiles
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Gable Roof
Hip
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Hip Roof
Ridge