6. WOOD LIGHT FRAME CONSTRUCTION
LIGHT WOOD FRAMING
Advantages
Flexible
Easily constructed
Economical
Disadvantages
Burns rapidly,
Decays if exposed to
moisture
Changes volume with
moisture changes
Framing unattractive (must
be covered)
6.1 WOOD LIGHT FRAME CONSTRUCTION - AN
OVERVIEW
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6.1 WOOD LIGHT FRAME CONSTRUCTION - AN OVERVIEW
6.2 INTRODUCTION TO BALLOON FRAME AND PLATFORM
FRAME
6.3 BALLOON FRAME
6.4 PLATFORM FRAME - ADVANTAGES AND
DISADVANTAGES
6.5 EIGHT STEPS FOR BUILDING A LIGHT WOOD FRAME
STRUCTURE
6.2 INTRODUCTION TO BALLOON FRAME AND
PLATFORM FRAME
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Advantages: Flexible - Any shape can be constructed - Has evolved over
150 years - Easily and swiftly constructed by hands, with a minimum amount
of tools
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Deficiencies: Rapid burning during fire - Decays fast exposed to dampness
- Expands and contacts significantly, causing cracking of plaster, sticking of
doors, buckling of floors, etc. - Can be controlled
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Two types: Balloon frame and Platform frame
- Advantages and
disadvantages
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Conventional Platform Frame - Built with 2” (nominal size)
members - connected with nails - Lumber aligned horizontally and vertically
and covered with sheathing - Floors and walls constructed - Sloping roof built
with header at lower edge and ridge boards at the the top
6.3 BALLOON FRAME
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In 1865, G.E. Woodward wrote ”A man and a boy can now attain the
same results, with the ease, that twenty men could on an old-fashioned
frame… the balloon frame can be put up for forty percent less money
than the mortise and tenon frame”
Framed solely with slender, closely spaced wooden members - Joist for
floors, studs for walls, and rafters for sloping roofs - Heavy beams were
eliminated
The full length studs ran continuously for two stories from foundation to
roof; hence not efficient for erection - The tall hollow spaces, in between
the studs, acted as multiple chimneys, spreading the fire very rapidly to
upper floors
6.3 Balloon Framing (Cont’d)
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“All” Light Wood Framing
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Full Length Studs
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Cost - Less than Timber
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Disadvantages
– Full length studs difficult to handle
– Hang 2nd floor platform
– No firestop
6.4 PLATFORM FRAME WITH ADVANTAGES AND
DISADVANTAGES
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Evolved from balloon frame after many modifications
Accepted now as the universal standard for wood light frame construction
Complex in details, but simple in concept
A floor platform is built, made up of either of a concrete slab on-ground or
with masonry/concrete footings - Wood load-bearing walls are erected upon
this floor/footings - A second floor wood platform is built on these walls Then a second set of walls is built on this platform - The attic and roof are then
built upon the second set of walls - Many variations are possible; one or two
stories tall, several types of roof (with or without attic) can be built
Advantages: Uses short, easily handled lengths of lumber for the vertical
framing - Vertical hollow spaces are automatically fire-stopped at each floor
level
6.4 Platform Frame (cont’d)
Advantages
 Short, easily handled lumber
 Made entirely of 2” lumber
 Automatic fire stop
 Working platforms
 Nail Connections
Disadvantage -Vertical shrinkage
6.4 PLATFORM FRAME …..
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(Cont’d)
Disadvantages: Each floor constitutes of a thick layer of wood, whose grain
runs horizontally - Leads to relatively large amount of vertical shrinkage in the
frame, as moisture dries from the wood - Can lead to distress in exterior/interior
finish surfaces
A conventional frame built entirely of 2” members (11/2 ” actual), with all
connections made with nails
Number of framing lumber are aligned parallel to one another, and nailed to cross
pieces; then covered with a sheathing (made up of a facing layer of boards, or
panels) that join and stabilize the pieces into a single structural unit - In a wall
structure, the vertical parallel pieces are called the studs, the cross pieces at the
bottom are the sole plates, and the cross pieces on top are called the top plates
In a floor, the parallel pieces are floor joists, and the cross pieces at the ends are
called headers, rim joists, or band joists. Sheathing on floor is called sub-floor
In a sloping roof, the rafters are headed off by the top plates at the lower edges of
the roof and by the ridge board at the peak
6.5 Building Sequence
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Plan / Design the Facility
– Establish Use, Owner Preference, Budget
– Consider Codes, Zoning & other Legal Requirements
– Graphically Communicate Building Design
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Foundations Design
Framing plans (identifies & locates framing members)
Architectural Floor Plans (locations, dimensions, walls, etc)
Exterior Elevations (details, openings, heights, finishes, etc.)
Interior Elevations & Sections (construction details, finishes, etc.)
Heating & AC, Plumbing, Electrical
6.5 EIGHT STEPS FOR BUILDING A WOOD LIGHT
FRAME STRUCTURE (Cont’d)
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Step 1: Establishing the position, shape, and size of the building
on site
- Erecting the batter boards, beyond the area to be excavated
- Corner stakes located with a plumb bob
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Step 2: Excavation and construction of the foundation and
substructure walls
- Excavating the foundations
- Form work built for walls
- Site-cast concrete foundation
- Slab-on-grade or other
- 4” layer of crushed stone, 3” to 4” thick concrete
- drainage for foundation
- Wall keyed to the floor slab
- Independent spread footings
Foundation Wall Systems
Sill
Anchor
Dampproofing
Stone for
Drainage
Perforated
Drainage
Pipe
Concrete or
CMU Wall
Drainage Stone
under SOG
often w/ Vapor
Barrier
Concrete
Strip
Footing
Thickened Slab-on-Grade
Load
Stone
Base
Thickened
SOG
Damp-proofing, Protection Board, & Drainage
Sequenced Photos of a Home Under Construction
Foundation
Foundation Materials
Reinforced Concrete
Concrete Masonry Units
Vapor
Barrier
Granular
SubBase
Foundation Insulation
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Insulate the Crawl Space
– Attach to Platform or on Ground
– Vapor Barrier
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Insulate the Exterior of the Wall
– Insulation exposed to the elements
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Insulate the Interior of the Wall
– Space & condensation considerations
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Insulation within the Wall (CMU)
6.5 EIGHT STEPS ……….
(Cont’d)
- Concrete wall built
- Interior steel pipe columns
- Exterior foam insulation for frost protection
- Batt insulation over plastic moisture barrier in crawl space in basement
- Drainage for walls
Step 3: Making the ground floor platform
- Floor framing plan
- Fire place and stair case opening
- Double header and trimmer joists at floor openings
- Bridging at mid-span
- Plywood sheets laid with their length directions perpendicular to joists
- Joining details
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Step 4: Framing of the ground floor walls
- Wall framing details
Building Sequence - Step Three
Erecting the Platform Frame
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Considerations
– Attachment
to the
Foundation
– Floor
Framing
– Sheathing
Attachment to the Foundation
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Sill Material
– Decay Resistant
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Termite Shield
Sill Attachment
– Anchor Bolts
– Expansion Bolts
– Add’l for Wind / Quake
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Set to Line & Elevation
Floor Framing
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- Spacing & Splicing
Spacing
– Factors Influencing Joist Spacing:
» Floor Loading (Minimums in Code) & Span Length
» Strength of Joist Material Used
» Sheathing (strength & size)
– Designation - Inches “o.c.” (on center)
» Typical - 16” oc (Other Typ. Options - 12” or 24”)
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Splicing
a) In - Line (w/ metal strap or wood)
b) Lapped
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Floor Framing Material
2” Material
(larger sizes optional)
Trusses
I-Beams
Wood,
Metal, or
Combination
Floor Framing
Bridging & Anchorage
Bridging
Joist Hanger
•Metal - Sized to Joist
•Purpose
Anchorage &
Support
•Material - Wood or Metal
•Purpose:
Improve Rigidity
Hold Joist Straight &
Distribute Loads
•Code requires for joists > 2x12
Wall Framing Layout
Framing Member Size & Spacing
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Loads - Vertical & Lateral
– Floor Loads, # of Stories, Roof Loads, Wind, Quake
– Minimum - Code Requirements
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Attachment of:
– Exterior and
– Interior Finishes
Opening Locations - Doors & Windows
 Insulation Requirements (may elect to use ‘deeper
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framing to accommodate thicker insulation)
Framing Terminology
Top Plate Often Doubled
Stud
Header
Sheathing
Sole Plate
Constructing the Wall Framing
Build on the Platform & Tilt-up or
 Build in Place
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Wall Framing
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6.5 EIGHT STEPS ……….
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(Cont’d)
Step 5: Building the upper-floor platform
- Details of second floor platform
- Interior stairways
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Step 6: Framing of the second-story walls
- Reinforcing against uplift
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Step 7: Framing of the attic floor and roof
- Roof framing and details
- Chimney details
- Dormer
- Hip rafter
- Roof framing
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Step 8: Completing the overall building frame
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Wall Sheathing
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Materials:
– Typically – OSB or Plywood
– Insulating Sheathing - (no structural qualities)
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Sheathing Purposes:
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Joins & stabilizes the structure
Resists uplift
Resists wracking- Resists lateral forces
Provides surface for finish material
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Roof Framing Built-in-Place Roof
Framing Built-in-Place
Ridge Board
Rafters
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Collar Ties
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Lookouts
Gable
Framing
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Note Strand
Orientation
Hurricane
Clip
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Roof Profiles
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Flat Roof
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Single Pitch
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Roof Profiles
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Gable Roof
Hip
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Hip Roof
Ridge
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Siding
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