4 HEAVY TIMBER FRAME CONSTRUCTION
History
• Simple timberframed
structures
appear with the
oldest known
civilizations.
• The traditional
braced frame
structure first
appears in the
middle ages.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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HISTORY
Contemporary
• Contemporary timber
frame construction may
be used for both
residential and
nonresidential
structures.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
4 HEAVY TIMBER FRAME CONSTRUCTION
FIRE-RESISTIVE
HEAVY TIMBER
CONSTRUCTION
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Resistance to Fire of Large Timbers
• Large wood
members have
greater resistance
to fire than
unprotected steel.
• Steel, due to its
high thermal
conductivity,
quickly heats up
and loses strength
during fires.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Resistance to Fire of Large Timbers
• Large timbers are slow
to absorb heat, slow to
catch fire, and slow to
burn.
• The charred outer layer
of a partially-burned
timber insulates and
protects the inner
undamaged portion of
the timber which
retains the capacity to
carry some load.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Heavy Timber
Construction
• Fire-resistive, traditional Mill
Construction consists of heavy
timber framing within brick
masonry exterior walls.
• In the contemporary building
code, Type IV Heavy Timber
construction requires heavy
timber framing within
noncombustible—masonry, steel,
or concrete—exterior walls.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Heavy Timber
Construction
• Timbers must meet minimum size requirements to qualify as
Type IV-HT construction in the building code.
• Members with lesser dimensions are classified as wood light
frame (Type V) construction.
Supporting Floor Loads
Supporting Roof and Ceiling Loads
Only
Columns
8 x 8 (184 x 184 mm)
6 x 8 (140 x 184 mm)
Beams and
Girders
6 x 10 (140 x 235 mm)
4 x 6 (89 x 140 mm)
Trusses
8 x 8 (184 x 184 mm)
4 x 6 (89 x 140 mm)
Decking
3 decking plus 1" finish (64 mm
decking plus 19 mm finish)
2" decking, or 1 1/8" plywood (38 mm
decking, or 29 mm plywood)
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Heavy Timber
Construction
In IBC, note how allowable heights and areas of
Heavy Timber (Type IV-HT) buildings exceed
those for unprotected steel (Type III-B).
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Heavy Timber
Construction
Allowable heights and areas of Heavy Timber
buildings also exceed those of light wood frame
(Type V) structures.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Wood Shrinkage
• Wood column/beam
connections are designed
to minimize the effects of
cross-grain shrinkage that
can lead to differential
settling between interior
framing and exterior walls
made of materials that are
not prone to shrinkage.
• Right: Traditional cast iron
pintle column base.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Wood Shrinkage
• Right: Contemporary
beam/column
connection with
bearing blocks, split
rings, steel straps.
• Note how beam ends
are not supported on
cross-grain material.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Beam Anchorage
• Fire cut beam
ends (right):
Collapse of
beam must not
topple
supporting
wall.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Beam Anchorage
• A ventilating
air space
around the
beam end
prevents
moisture in the
masonry wall
from seeping
into the beam.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Beam Anchorage
• Upper clip
restrains beam
from side-to-side
movement while
allowing rotation
due to structural
deflection or
beam collapse in
a fire.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
FIRE-RESISTIVE HEAVY TIMBER CONSTRUCTION
Floor and Roof Decks
• Decking comes in
depths of 2" to 8",
capable of spanning
roughly from 5' to more
than 20'.
• To achieve the required
fire-resistance, floor
decking must be covered
with tongue-and-groove
boards or plywood.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
HEAVY TIMBER CONSTRUCTION
Floor and Roof Decks
• Fire-resistive
heavy timber
floors and roofs
must be
constructed
without
concealed
cavities where
fire could
develop
undetected.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
LATERAL BRACING
Bracing Heavy Timber Structures
• HT structures
may be braced
against lateral
forces with
diagonal framing
members, shear
walls of masonry
or concrete, or
rigid panels
attached to the
building frame.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
LATERAL BRACING
Bracing Heavy Timber
Structures
• To meet
contemporary
standards, historical
structures may
require insertion of
new steel or
reinforced concrete
bracing elements.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
LATERAL BRACING
Bracing Heavy Timber Structures
• Floor and roof
diaphragms must also
be securely tied to the
supporting structure.
• Right: New OSB,
metal straps, and
structural angles tie
the floor structure of
an historic mill
building to its
masonry walls.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
HEAVY TIMBER CONSTRUCTION
Building Services
• When floor and
roof systems
cannot have
concealed spaces,
services such as
lighting, ductwork,
sprinkler piping,
electrical wiring
must be routed in
the open.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
4 HEAVY TIMBER FRAME CONSTRUCTION
CONNECTIONS
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
CONNECTIONS
• Knee bracing
with traditional,
pegged mortise
and tenon
joinery
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
CONNECTIONS
• Proprietary fastening system with self-drilling steel
dowels and concealed steel plates
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
CONNECTIONS
• Fabricated steel seat, concealed plates, and exposed
through-bolts
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
CONNECTIONS
• Steel plate gusset with tie rod and through-bolts
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
CONNECTIONS
• Copper sheet metal flashing to protect against moisture
absorption at vulnerable ends of large timbers exposed
to the weather
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
4 HEAVY TIMBER FRAME CONSTRUCTION
LONGER SPANS IN
HEAVY TIMBER
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
LONGGER SPANS IN HEAVY TIMBER
Large Beams
• Glulam
beams can
span over 80',
and arches
even further.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
LONGGER SPANS IN HEAVY TIMBER
Trusses
• Heavy timber
trusses can span
beyond 200'.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
LONGGER SPANS IN HEAVY TIMBER
Domes
• The
Washington
State Tacoma
Dome spans
530'.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.