Chapter 05 Wood Light Frame Construction

Fundamentals of Building Construction, Materials & Methods, 6th Edition
Copyright © 2013 J. Iano. All rights reserved.
5 WOOD LIGHT FRAME CONSTRUCTION
PLATFORM
FRAME

Platform Frame
Balloon Frame
Small-dimension members
span from ground floor to
roof.
• North-American invention
• Light wood frame uses
lighter wood members,
simpler nailed connections
• Requires less skilled
builders

Platform Frame
Precursor technologies:
• Water- or steam-powered
saw mills
• Machine-made nails
• Railroad transportation

Platform Frame
Platform Frame
Relies on shorter
length, single-story
height members
that are easier to
produce, handle,
and erect.

Platform Frame
Platform Framing
Platform…walls…platform…walls…

Platform Frame
• Nominal 2-inch
members (1-
1/2” wide)
• Spaced at 16" or
24“ on center
• Floor, ceiling:
joists
• Wall: studs
• Roof: rafters

Platform Frame
Panels applied over
framing:
• Floor:
subflooring
• Wall and roof:
sheathing
• OSB, plywood,
or other material

Platform Frame
OSB (Oriented
Strand Board):
engineered wood,
formed by adding
adhesives and then
compressing layers
of wood strands
(flakes) in specific
orientations.

Platform Frame
Plywood: an
engineered wood
material manufactured
from thin layers or
"plies" of wood veneer
that are glued
together, with each
layer having its grain
rotated 90 degrees
from the next layer
and giving the sheet
strength in all
directions.

FOUNDATIONS
FOR LIGHT
FRAME
STRUCTURES

Foundations for Light Frame Structures
Residential Basement Foundation
Excavation to
necessary depth
of basement (and
at least below the
frost line).
Temporary batter
boards, tautly
strung together,
mark the location
of the faces of the
structure.

Cast-in-place
concrete strip
footing
Cast-in-place
concrete
foundation
wall, 8" to 12"
thick, 8' to 10'
tall

• Anchor bolts cast into
the top of the
foundation wall attach
to the lumber framing.
• Steel reinforcing is also
located at the bottom
of the wall, connecting
the wall to the
concrete footing.

• Dampproofing or
waterproofing is applied
on the outside of the
wall to prevent the
concrete from ‘wicking
up’ moisture from the
earth.
• Crushed stone and
perforated perimeter
drain help drain
moisture away from the
foundation.

• Backfilled soil is placed
in the gap between the
excavation and the
foundation after the
first-floor platform is
erected and can brace
the foundation walls.

Foundation Insulation Strategies
The amount and
location of foundation
insulation varies with
the severity of the
climate.

Top Left: Foam plastic
insulation on the outside
of walls reduces heat
loss through the
foundation, protects the
exterior damproofing
during backfilling, and
reduces the potential for
condensation on
surfaces in the
basement.

Top Right: Rigid insulation
can be applied to the
inside face of foundation
walls in existing buildings,
or to reduce the risk of
termite infestation
through the cellular
channels of the insulation.
It must be covered by
gypsum board (not
shown) to limit toxic gases
produced in a fire.

Bottom Left: Crawl spaces
under the first floor can be
insulated with batt
insulation on the interior
surfaces, to protect
against the loss of heated
air to the exterior. This
method is used in a mild
climate.

Bottom Right: When a
crawlspace is ventilated
to the exterior, the floor
platform above must be
insulated to protect
against heat loss. Rigid
insulation underneath
the floor joists protects
the joists and batt
insulation between them
from high humidity in
the crawlspace.

A vapor barrier sheet,
applied to the ground
surface, inhibits the
absorption of moisture
into the crawlspace air
and limits humidity in
the space.

Cast-in-place concrete foundation wall
with anchor bolts protruding
Note pockets in far side of concrete
wall for setting of floor beams.

Exterior
foundation
insulation:
Expanded
polystyrene
rigid foam

BUILDING THE
FRAME

Building the Frame
Ground Floor Platform
• Sill plates
anchored
• Girders
placed
• Floor joists
laid
• Subflooring
applied

Building the Frame
Section
• Sill plates
anchored
• Girders
placed
• Floor joists
laid
• Subflooring
applied

Building the Frame
Preservative-
treated 3x8 sill
plate with
closely spaced
anchor bolts

Building the Frame
Oversized square
washers create a
stronger sill-to-
foundation
connection, for
resistance to
seismic forces.

Building the Frame
Floor framing with 2x12 solid member
joists

Building the Frame
Wall sections are
assembled lying
down, then tilted
into place.
Temporary
bracing holds
walls in
alignment.

Building the Frame
Wall sheathing
may be applied
before the walls
are stood up, or
later, after the
frame is fully
erected (as
shown here).

Building the Frame
Section:
• Sole plates are
nailed to the floor
platform.
• Studs run
continuously
between sole and
top plates.

Building the Frame
Top plates are
doubled, to
support joists or
rafters above.
The top plate
ends are
staggered to tie
separate wall
sections together.

Building the Frame
Framing at
corners
provides
nailing
surfaces for
interior
wallboard
and
exterior
sheathing.

Building the Frame
Rough Opening
Jack studs
support the
header.
The header
supports the
loads above
the opening.

Building the Frame
Walls are
constructed
in sections,
lying down
on the floor
platform
and then
tilted up
into
position.

Building the Frame
Adjustable,
bowed
springboards
allow precise
alignment of
the walls.

Building the Frame
Window rough
opening, viewed
from the inside,
with the window
installed.

Building the Frame
Bottom section of
sheathing is
preservative
treated plywood, to
protect from decay
at raised grade on
exterior side.
Upper portion is
OSB.

Building the Frame
A Glulam
(engineered
composite of
wood
laminations)
beam spans a
large garage
door opening.
Such a span
would require a
large, heavy,
and expensive
lumber header.

Building the Frame
Lateral Force Resistance
• Sliding
• Overturning
• Wracking
• Failure among parts

Building the Frame
Anchor
bolts
resist
sliding.

Building the Frame
Hold-downs
resist
overturning.
(Will be nailed
over sheathing
after sheathing
is applied).

Building the Frame
A heavy-duty
hold-down to
resist high shear
forces, such as
hurricane activity.

Building the Frame
Shear walls
resist
wracking:
Plywood
sheathing

Building the Frame
With high lateral
forces, special
nailing is required to
ensure adequate
load transfer and
prevent failure
among parts.

Building the Frame
Any solid
sheathed area
may act as a
shear wall.
Interior walls,
properly
constructed,
can also act as
shear walls.

Building the Frame
Higher strength prefabricated
assemblies may be used where solid
wall area is limited.

Building the Frame
Metal
strapping is
one form of
collector
used to
transfer
forces
between
parts.

Building the Frame
Upper Floor Platform
Upper floor
framing much
the same as
ground floor.

Building the Frame
Section Drawing: Rim joists and
interior blocking close off joist spaces
and prevent the joists from tipping.

Building the Frame
An alternative to working with lumber is the use of
pre-manufactured I-joists. These structural
components are lighter in weight, can span greater
distances, provide greater straightness and
uniformity, and reduce drying shrinkage of the floor
platform than ordinary lumber components.

Building the Frame
With I-joists, the thinner OSB webs (middle
sections) require stiffeners, blocking, or squash
blocks to support loads from above without
buckling.

Building the Frame
I-joist framing
seen from
below.
Note web
stiffeners at
joist ends.

Building the Frame
I-joist framing
seen from
above.

Building the Frame
Upper Floor Walls
Each floor
platform makes a
convenient work
surface for
building the next
set of walls.

Building the Frame
Roof Framing
Ceiling joists and
roof rafters are
erected on top of
the upper floor
walls.

Building the Frame
A knowledgeable
framer can lay out all
cuts on a sloped rafter
with nothing more
than a traditional
framing square and
pencil.

Building the Frame
Collar ties, close to the
upper ends of the
rafters, resist wind
uplift forces.
Ceiling joists, close to
the lower ends of
rafters, resist the
rafter horizontal
spreading forces that
could cause the walls
to spread outward.

Building the Frame
Solid
lumber
rafters in
a gable
roof and
dormer.

Building the Frame
When rafters are not tied at
the lower ends with ceiling
joists, as in an attic, a
structural ridge beam (steel
in this example) is required
to prevent the ridge from
sagging and the rafters
from pushing outward on
the tops of the walls.

Building the Frame
The complex
cuts required for
hip framing
(shown here) or
valley framing
can also be laid
out with just a
framing square.

Building the Frame
Pre-
fabricated
roof trusses
with
temporary
bracing

Building the Frame
A fully-framed
and sheathed
structure.
Rough
Carpentry has
concluded,
and Finish
Carpentry
work at the
roof eaves has
begun.

Chapter 05 Wood Light Frame Construction

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Chapter 05 Wood Light Frame Construction