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Prescriptive Residential Wood Deck Construction Guide
John “Buddy” Showalter, P.E.
Vice President, Technology Transfer
American Wood Council
Michelle Kam-Biron, PE, SE, SECB
Director of Education
American Wood Council
Copyright © 2013 American Wood Council. All rights reserved.
www.awc.org
Copyright Materials
This presentation is protected by US and
International Copyright laws. Reproduction,
distribution, display and use of the presentation
without written permission of the speaker is
prohibited.
© American Wood Council 2013
Copyright © 2013 American Wood Council
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Downloads
DCA6 Deck Guide
http://www.awc.org/publications/DCA/DCA6/DCA
6-09.pdf
DCA6 Presentation
http://www.awc.org/pdf/DCA6-Decks-webinarAug2013.pdf
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Resources
Forest Products
Society
Wood Design Focus
http://www.forestprod.org/
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Objectives/Outline
 Identify minimum prescriptive
wood deck requirements
 Describe minimum material
requirements for deck
construction including wood
members and fasteners
 Discuss design requirements
and resources if prescriptive
limits are exceeded
 Provide a deck design
example
 Discuss durability issues (will
not be covered)
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Why is this Important?
News reports on deck collapse
Compiled by Dr. Frank Woeste
• 66 reports from 1996-2007
• 500+ injuries
• 17 deaths
• Example:
• Chicago, IL - June 2003
• 13 dead
• 40+ injured
Copyright © 2013 American Wood Council
Copyright © 2013 American Wood Council
“Except for hurricanes and tornadoes,
more injuries may be connected to deck
failures than all other wood building
components and loading cases
combined!”
Dr. Frank Woeste, P.E.
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DCA 6
Prescriptive Residential Wood Deck Construction Guide – Design for Code Acceptance No. 6 (DCA 6)
Primary Cooperators
 American Wood Council
 International Code Council
 Fairfax County Virginia
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DCA 6
 Additional Cooperators
 APA-The Engineered Wood Association
 National Association of Home Builders
 North American Deck & Railing
Association
 Simpson Strong-Tie Company
 Southern Forest Products Association
 Southern Pine Inspection Bureau
 Stairway Manufacturers’ Association
 Virginia Polytechnic Institute and State
University
 Washington State University
 WTCA-Representing the Structural
Building Components Industry
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DCA 6
 Basis and Applicability
 2009 International Residential Code (IRC)  bracketed text shows reference to applicable IRC sections ex. [R317 and R318].  Recommended prescriptive construction methods meet or exceed IRC minimum requirements
 Provisions not included in IRC are considered good practice recommendations
 Where differences exist, IRC applies
 Not intended to preclude use of other construction methods or materials
 All construction and materials approved by the authority having jurisdiction
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DCA 6 Outline
Commentary!!!
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Minimum Requirements
 Single level residential decks
only
 Hot tubs outside scope
 Does not apply for snow loads,
snow drift loads, or sliding snow
loads that exceed 40 psf
 Does not address wind or
seismic design issues
 Decks shall not be used or
occupied until final inspection
and approval is obtained
 Alternate methods and materials
approved by the building official
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Objectives/Outline
 Identify minimum prescriptive
wood deck requirements
 Describe minimum material
requirements for deck
construction including wood
members and fasteners
 Discuss design requirements
and resources if prescriptive
limits are exceeded
 Provide a deck design
example
Copyright © 2013 American Wood Council
Copyright © 2013 American Wood Council
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Minimum Requirements
Lumber
• American Lumber Standards Committee (ALSC) approved grade mark
• Naturally durable
• Redwood or Western Cedar
• Preservative treated
• American Wood Protection Association (AWPA)
• Ground contact
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Minimum Requirements
 Fasteners
 Nails – ASTM F 1667
• Threaded nails as stated in this
document include helical (spiral)
and annular (ring-shank) nails.
 Screws – ANSI/ASME B18.6.1
 Bolts/Lags – ANSI/ASME B18.2.1
 ½″ bolts and lag screws
prescribed extensively
 Edge distance and spacing based
on diameter
 Need to adjust for larger or smaller
fasteners
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Minimum Requirements
 Corrosion Resistance 2009 IRC R317.3
 Screws, bolts, nails
•
•
•
•
Hot-dipped galvanized
Stainless
Silicon bronze
Copper
 Hangers and anchors
• Galvanized
• Stainless
 Saltwater exposure
• Stainless
 Other fasteners/hardware
• Approved by building official
 Flashing
• Nominal 0.019” min.
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Minimum Requirements
 Corrosion Resistance
 2009/2012 IRC
R317.3 Fasteners and
connectors in contact with
preservative-treated and fireretardant-treated wood.
Fasteners, including nuts and
washers, and connectors in
contact with preservativetreated wood and fireretardant-treated wood shall be
in accordance with this
section. The coating weights
for zinc-coated fasteners shall
be in accordance with ASTM A
153.
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Minimum Requirements
 Corrosion Resistance – 2009/2012 IRC
R317.3.1 Fasteners for preservative-treated wood. Fasteners, including
nuts and washers, for preservative treated wood shall be of hot-dipped,
zinc-coated galvanized steel, stainless steel, silicon bronze or copper.
Coating types and weights for connectors in contact with preservativetreated wood shall be in accordance with the connector manufacturer’s
recommendations. In the absence of manufacturer’s recommendations, a
minimum of ASTM A 653 type G185 zinc-coated galvanized steel, or
equivalent, shall be used.
Exceptions:
1.
2.
3.
One-half-inch-diameter (12.7 mm) or greater steel bolts.
Fasteners other than nails and timber rivets shall be permitted to be
of mechanically deposited zinc-coated steel with coating weights in
accordance with ASTM B 695, Class 55 minimum.
Plain carbon steel fasteners in SBX/DOT and zinc borate preservativetreated wood in an interior, dry environment shall be permitted.
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Decking
 Dimension lumber (2″ nominal)
 Span rated decking
 ALSC decking policy
 Attachment
 2-8d commons
 2-#8 screws
 Spacing 1/8″
 Perpendicular or 45°
 Bear on 4 joists minimum
 Substitution
 Approved by building official
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Joists
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Joists
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Joists
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Joists
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Joists
• Span table development – without overhangs
–
–
–
–
–
40 psf uniform live load
10 psf uniform dead load
No. 2 Grade
L/360 Deflection Limits
Wet Service Condition
LJ
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Joists
• Span table development – with overhangs
–
–
–
–
40 psf uniform live load
10 psf uniform dead load
No. 2 Grade
Wet Service Condition
LJ /4
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Copyright © 2013 American Wood Council
LJ
LJ /4
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Joists
• Span table development – with overhangs
– L/180 cantilever deflection limit
– 220 lb. point load at the end of cantilever
220 lbs.
LJ /4
LJ
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Joists
220 lb
point
load
controls
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Joists
• AWC Online Span Calculator
–
–
–
–
–
Simple spans (no cantilever)
Uniform loads
Wet service conditions
Incising factor
18’-0” MAX (DCA 6)
Free at www.awc.org
Apps – not free
28
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Joists
• Incising factor
– Refractory
species
– DFL, HF, SPF
– Reduces
strength and
stiffness
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Joists
Incising factor
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Joists
DCA6 – Southern Pine Changes
http://awc.org/publications/DCA/DCA6/DCA6‐09.pdf
Copyright © 2013 American Wood Council
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Beams
• Spans
– L/4 maximum overhang
– Splice over posts
– Joists cannot be attached to opposite sides of the same beam
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Beams
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Beams
DCA6 – Southern Pine Changes
http://awc.org/publications/DCA/DCA6/DCA6‐09.pdf
Copyright © 2013 American Wood Council
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Beams
• Assembly
– For built-up beams
– 10d threaded or #10 wood
screws
– 16″ o.c. staggered
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Framing Plan
Southern Pine
2
3
12
10
11
12
700
12
2 12
1500
10
25
23
23
10
2
2
4
24
12
10
6
0
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Joist‐to‐Beam Connections
• Options
– Toe-nails
– Hurricane clip
– Joist hanger
LJ
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Copyright © 2013 American Wood Council
LJ /4
LJ
LJ /4
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Joist‐to‐Beam Connections
• Joist Hangers
– Capacity per Table 3A
– Galvanized
– No clips/brackets
DCA6 Addendum
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Post Requirements
•
•
•
•
6x6 or larger
Max. 14′ height
Centered on footings
Cut ends field treated
– Copper naphthenate
– [R402.1.2]
• Post-to-Beam
– Notch
• 3x or 4x beam
• 2-ply beam
• Two ½″  bolts w/ washers
– Post cap
• 3-ply beams
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Post Requirements
• Prohibited connection
– Beam to side of post
– Ensures wood-to-wood bearing
– Avoids potential issues with
non-compliant fasteners
– Bolts in wet service
environments have reduced
capacity
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Rim Joist Requirements
• Decking attachment
– #10 x 3″ min. wood screws @
6″ o.c.
– 10d threaded nails @ 6″ o.c.
Copyright © 2013 American Wood Council
Copyright © 2013 American Wood Council
• Joist attachment
– (3) #10 x 3″ min. wood screws
– (3) 10d threaded nails
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Footings [R403]
• Depth > 12″ or frost line
• Soil 1,500 psf bearing capacity
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Footings
• Sizes
– Square footings 2″ less than
round
– 1,500 psf soil bearing
– 2,500 psi concrete strength
– Coordinate thickness with
anchors
• Anchor length < footing
thickness
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Ledger Requirements [R502.2.1] • Ledger board depth > deck joist depth • Flashing with drip edge
– Corrosion resistant
• Ledger board depth < rim joist depth
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Deck Stability – Lateral Loads
2012 IRC
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Ledger Requirements
• Ledger board to foundation wall
– Concrete or solid masonry
– ½″ approved anchors
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Ledger Requirements
• Ledger board to foundation wall
– Hollow masonry
– ½″ approved anchors
– Grout at anchor locations
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Ledger Requirements
•
I-joists
– 1″ or thicker EWP band joist
• OSB
• SCL including LVL
– <1″ band joist
•
• Free standing deck
• Full plan submission
Trusses
– 2x4 ribbon
• No deck attachment
– Requirements
•
•
•
•
Standard details
Free-standing deck
Full plan submission
SBCA tech note www.sbcindustry.com
48
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Prohibited Ledger Attachment
• Exterior veneers
– Brick
– Masonry
– Stone
• Requires free-standing deck
Photo courtesy of John Bouldin. All rights reserved.
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Prohibited Ledger Attachment
• Cantilevered floors
• Bay windows
• Requires freestanding deck
50
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Deck Ledger Testing
• Virginia Tech & Washington
State University
• 3 common conditions
• ½″ diameter lag screws & bolts.
• Fastener spacing values limited
to:
– Deck live load of 40 psf and 10 psf
dead
– Band joist lumber with G ≥ 0.42
– Composite rim board with thickness ≥
1″ and equivalent G ≥ 0.50
– PPT deck ledger lumber with G ≥ 0.43
– Deck ledger can be incised and wet
– Proper installation including flashing
– No decay present
– No fastener corrosion
Copyright © 2013 American Wood Council
Copyright © 2013 American Wood Council
Photo courtesy of Frank Woeste and Joseph Loferski. All rights reserved.
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Ledger Board Fasteners
• IRC Table R502.2.2.1 modified to include EWP rim boards
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Ledger Board Fasteners
IRC 2012
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Ledger Board Fasteners
• Bolts
• Placement
–
–
–
–
2″ min. for top row
2″ min. from ends
Staggered in 2 rows
Bottom row depends on
ledger depth
– 5″ max. between rows
– ½″ diameter with washers
– Pilot holes
• Expansion/Adhesive Anchors
– ½″ diameter with washers
– Concrete or solid masonry
– Hollow masonry with grouted cells
– Embedment length per manufacturer
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Ledger Board Fasteners
IRC 2012
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Ledger Board Fasteners
• Lag Screws
• Lag Screw Installation
– ½″ diameter with washers
–
– Threads in band board
– Extend ½″ beyond band board
–
–
–
–
Pilot holes
• ½″ diameter in ledger
• 5/16″ diameter in band board
Insert by turning
Do not hammer
Soap or lubricant
Snug but not over-tightened
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Free Standing Deck
•
•
•
•
To resist vertical loads
Located within L/4 of wall
Deck and house footings same elevation
Caisson minimizes excavation by basements
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Deck Stability
• Decks > 2′ above grade • Parallel to beam
– require diagonal bracing
– Attach to exterior wall
– Bolt to beam and post
• Perpendicular to beam
– Bolt to post and joist or blocking
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Deck Stability – Lateral Loads
• Attachment to
House – Freestanding Deck
– 3/8″ ext. wall
sheathing
– 16″ o.c. fasteners
staggered
– Flashing over rim
joist
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Deck Stability
Brian J. Parsons, Donald A. Bender, Ph.D., P.E., J. Daniel Dolan, Ph.D., P.E., and Frank E. Woeste, Ph.D., P.E. Copyright © 2013 American Wood Council
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Deck Stability
• Attachment to
House – Deck
Supported by
Ledger
– Lateral
attachment to
house floor
system
– 2009 IRC
– 2 locations per
deck
– 1500 lb capacity
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Deck Stability – Lateral Loads
2012 IRC
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Guard Requirements
• Decks > 30″ above grade require guard
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Guard Requirements
Adjacent Fixed Seating
Requirement
• 36″ measurement from seat
R312.2 Height. Required guards at
open-sided walking surfaces,
including stairs, porches, balconies
or landings, shall be not less than
36 inches (914 mm) high measured
vertically above the adjacent
walking surface, adjacent fixed
seating or the line connecting the
leading edges of the treads.
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Guard Post Testing
• IBC/IRC require guard
rails to resist 200 lb
concentrated load
• Tests require 2.5
safety factor per IBC
• Virginia Tech
Research
– Typical ½″ bolt or lag
screw connections failed
– Commercial hold down
passed
Photo courtesy of Frank Woeste and Joseph Loferski. All
rights reserved.
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Guard Requirements
• Minimum 4x4 post
• Bending design value > 1,100 psi
– All No.2 species shown in Table 2
– CM = 0.85, Ci = 0.80, CD = 1.6
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Guard Requirements
• Guard Post to Rim Joist
– Hold down anchors
– Minimum of two ½″ bolts
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Stair Requirements
• Treads and Risers
– 7-3/4″ rise & 10″ run
– Except where
amended
– 1x risers
– Treads per Table 6
– Openings < 4″
diameter sphere
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Stair Requirements
• Stringers
– Minimum 2x12
– Spans per Figure 28
– Intermediate landings
permitted
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Stair Requirements
DCA6 – Southern Pine Changes
http://awc.org/publications/DCA/DCA6/DCA6‐09.pdf
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Stair Requirements
• Stringers
– Cut < 18″ o.c.
– Solid < 36″ o.c.
• Treads
– Sizes per Table 6
– Connections per
Fig 29
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Stair Requirements
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Stair Requirements
DCA6 – Southern Pine Changes
http://awc.org/publications/DCA/DCA6/DCA6‐09.pdf
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Stair Requirements
• Guard Requirements
– Required if 30″ total rise
– 6′ maximum between
posts
– 34″ height minimum
– Opening <6″ diameter
sphere
– Openings <43/8″ for
tread guards
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Stair Requirements
• Stringer Attachment
– Hangers
• Sloped joist hanger
• Per manufacturer
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Stair Requirements
• Handrails
– Required for stairs
with 4 or more treads
– Height 34″ – 38″
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Stair Requirements
• Handrails
– Type I: 4″ – 6¼″
perimeter
• Circular
– 1¼″ – 2″
diameter
• Noncircular
– Max. cross
section 2¼″
– Type II: >6¼″ perimeter
• Graspable recess
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Stair Requirements
• Handrails
– Continuous from
lowest to highest
riser
– Return to guard at
each end
– May be interrupted
by guard at turn
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Stair Requirements
• Stair Footings [R403]
–
–
–
–
12″ min. depth or frost line
10″ square or 12″ diameter
6″ thick
4x4 posts centered
• Bearing Block
– 2x4
– 8 fasteners
• Stringer
– ½″ bolts only if guard is
required
• Lighting
– Top landing
– Illuminate all landings
– Light switch inside the house
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Framing at Chimney or Bay Window
• Headers 6′ maximum span
– Use 6x6 post to reduce spans to <6′
– >6′ span requires plan submission
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Framing at Chimney or Bay Window
• Trimmers
– Triple
• 12"-16" joist
spacing
• Spans > 8'-6"
– Double
• 24" joist
spacing
• Spans < 8'-6"
– “a” < 3'
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DCA 6 Commentary
Joist Typ.
Beam
• Background information
• Example calculations
• Alternate prescriptive provisions
– Ex: Joists framing into 2 sides of the same beam
•
•
8′-0″ joists from opposite sides
Use 16′-0″ joist spans for equivalent tributary area
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Footing Design
DCA 6 Commentary
Post load: R
L 
 L L  L
R  50 J  J  B  B 
4  2
4 
 2
Square footing: Round footing: R
1500
B  12
D  12
5.5″
P
T
4R
1500
B or D
Footing thickness: T > P; Copyright © 2013 American Wood Council
Copyright © 2013 American Wood Council
D  5. 5
T
2
Figure C12. Footing dimensions and variables.
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Footing Design
DCA 6 Commentary
 Table C4 - additional
footing
diameters/thicknesses
not shown in Table 4


Assumes 1,500 psf soil
bearing capacity
Assumes 2,500 psi concrete
compressive strength
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Objectives/Outline
 Identify minimum prescriptive
wood deck requirements
 Describe minimum material
requirements for deck
construction including wood
members and fasteners
 Discuss design requirements
and resources if prescriptive
limits are exceeded
 Provide a deck design
example
Copyright © 2013 American Wood Council
Copyright © 2013 American Wood Council
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Additional Resources
 2005 National Design
Specification® (NDS ®) for
Wood Construction
 Structural lumber
• Design values
• Grading rules
 Column design
 Beam design
 Connection design
 Footing design
 Per engineering mechanics
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Design Values
Structural Lumber Classifications
 Dimension Lumber
 Rectangular or square cross-section
 2" - 4" thick and 2" or more wide
 Beams and Stringers
 Rectangular cross-section
 6" x 8" and larger
 Graded for strength in bending on
narrow face
 Posts and Timbers
 Square or nearly square crosssection
 5" x 5" and larger
 Graded for use as posts
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Additional Resources
 2012 National Design
Specification® (NDS ®) for
Wood Construction
 Structural lumber
• Design values
• Grading rules
 Column design
 Beam design
 Connection design
 Footing design
 Per engineering mechanics
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Design Values
Structural Lumber
Classifications
 Dimension Lumber
 Rectangular or square cross-section
 2" - 4" thick and 2" or more wide
 Beams and Stringers
 Rectangular cross-section
 6" x 8" and larger
 Graded for strength in bending on
narrow face
 Posts and Timbers
 Square or nearly square crosssection
 5" x 5" and larger
 Graded for use as posts
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Design Values
 Design values are assigned to predict strength
and stiffness properties to meet engineering
design requirements
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Design Properties ‐ Bending
Fiber Stress in Bending Fb
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Design Properties ‐ Compression
Compression Parallel to Grain Fc||
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Design Properties ‐ Tension
Tension Parallel to Grain Ft
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Lumber Adjustment Factors
Most common
adjustment factors
for decks
Beams/Joists
Columns
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Load Duration Factors
Assumption
for decks is
occupancy live
load
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Load Duration Curve
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Size Adjustment Factor
Common for joists/beams
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Repetitive Member Factor, Cr
 2"- 4" dimension lumber
 24" o.c. or less
 3 or more members
 Load distributing element
 Applies to Fb
Cr = 1.15
 For decks:
 Joists
 Built-up beams
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Wet Service Factor, CM
• Note the adjustment
is unity if:
FbCF < 1150 psi
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Incising Factor, Ci
 Sawn Lumber Refractory Species
 Increase
Preservative
Penetration
 0.4" Depth
 3/8" Length
 1100 teeth / ft2
density
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Incising Factor, Ci
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Adjustment Factors ‐ Example
 No. 2 grade, 2x8 Hem Fir
deck joist, 16" o.c., incised,
wet use, tabulated Fb = 850
psi




CF = 1.2
CM = 1.0
Ci = 0.80
Cr = 1.15
 Allowable Fb' is:
850(1.2)(1.0)(0.80)(1.15) = 938
psi
 Used to calculate joist spans
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Column Design
 Columns and posts must
be designed for stability
and load carrying capacity
 Tributary area
 Floor/deck load
 Column or post length (height)
 Design of solid columns
with unbraced lengths in
either the strong or weak
axis requires buckling
analysis in accordance
with NDS 3.7
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Post Height for DCA 6
 6x6 minimum
 4x4 Alternate
 DCA 6 Commentary
 Southern pine – 10' max.
 Other species – 8' max.
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Beam/Joist Design
 Beam/Joist Spans are based on:
 Species and grade of lumber
 Cross-sectional size of beam
 Tributary load it supports
 Design Considerations




Bending
Shear
Deflection
Bearing
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Joist/Beam Design ‐ Notches
 Notching Provisions – Sawn Lumber
 NDS 3.2.3 & R502.8
OUTER THIRD
OF SPAN ONLY
DEPTH, MAX.
1/4 JOIST
1/3
JOIST
DEPTH, MAX.
1/6 JOIST
DEPTH, MAX.
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Column and Beam Design
 Tables simplify process
 Wood Structural Design
Data (WSDD)
 Column load tables
 Beam load tables
 Requires adjusted design
values
 Free at www.awc.org
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Column and Beam Design
 Tables simplify process
 Wood Structural Design
Data (WSDD)
 Column load tables
 Beam load tables
 Requires adjusted design
values
 Free at www.awc.org
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Span Tables for Joists and Rafters
 Floors, ceilings, rafters
 Loads
 Dead loads - 5, 10, & 20 psf
 Live loads - 20, 30, 40, 50, & 60 psf
 Deflection criteria
• L/180, L/240, & L/360
• Adjustment factors for L/480 & L/600
 Design value adjustments





Size factor
Repetitive member
Load duration
Wet service
Incising
 Free at www.awc.org
 Span table tutorial
http://www.awc.org/technical/spant
ables/tutorial.html
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Span Calculator
• AWC Online Span Calculator
–
–
–
–
Simple spans (no cantilever)
Uniform loads
Wet service conditions
Incising factor
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Connection Design
• NDS design values
–
–
–
–
Equations
Tables
Penetration
Spacing, end, and edge
distance
– Tension perpendicular to grain
• Materials
– Wood to wood
– Wood to steel
– Wood to concrete
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NDS Capacity Tables
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NDS Connection Calculator
•
•
•
•
Single fasteners
All 6 yield modes
ASD and LRFD
Free at
www.awc.org
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Spacing, End, & Edge Distances
Parallel to Grain
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Spacing, End, & Edge Distances
Perpendicular to Grain
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Connecting Wood
wood and tension perpendicular to
grain
 the evil of wood connections
initiators:
• notches
• large diameter fasteners
• hanging loads
• shrinkage
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Tension Perpendicular to Grain
These are no‐no’s!
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Wet Service Factor, CM
CM = 1.0 if:
Saturated
1 fastener
19% MC
fabrication MC
in-service MC
2+ fasteners
Dry
CM
0.4
Lateral load (D>1/4″)
split splice
plates
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Objectives/Outline
 Identify minimum prescriptive
wood deck requirements
 Describe minimum material
requirements for deck
construction including wood
members and fasteners
 Discuss design requirements
and resources if prescriptive
limits are exceeded
 Provide a deck design
example
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Deck Design Example 1
Beam
 Deck height = 2'-0"
 8' x 12' deck surface
 Structural members: southern pine
 Decking: 5/4 radius edge southern
pine decking
 48" frost line
Joists
Deck
House
 Determine sizes for joists, beams,
hangers, footings, stringers, and
treads
 Determine fastener spacing for lag
screws in southern pine house rim
board
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Deck Design Example 1
 Joist Size for 8′ span dimension (w/out overhang)
 DCA 6 Table 2
 2x8 @ 24″ o.c.
 Cantilever has same max span
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Deck Design Example 1
 Beam Size for 12′ span dimension





 Try 3-2x8: spans 9′-6″
DCA 6 Table 3
 LB/4 = 9′-6″ /4 = 2′-4½″
 9′-6″ + 2′-4½″ + 2′-4½″ =
For 8′ joist span
14’-3” > 12” OK
Try 2-2x8: spans 7′-7″
 Use 8′ span with 2′
LB/4 = 7′-7″ /4 = 1′-10¾″
overhangs at each end
*2‐2x10 also works
7′-7″ + 1′-10¾″ + 1′-10¾″ = 11′-4½″ < 12’ NG
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Deck Design Example 1
 Joist Hanger Size
 DCA 6 Table 3A
 For 2x8
 500 lb joist hanger
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Deck Design Example 1
 Footing Size





DCA 6 Table 4
Thickness = 6″
Square = 15″
Round  = 17″
Below frost line
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Deck Design Example 1
 Ledger Fastener Spacing




Assume 2x10 southern pine house rim board
Assume 2x8 southern pine ledger
DCA 6 Table 5
½″ lag screws @ 18″ o.c.
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Deck Design Example 1
 Stair Stringers
 DCA 6 Figure 28
 2′ deck height
 Requires 2′-6″ cut
stringer span assuming
7¾″ rise and 10″ run 6’0” > 2’-6” ok
 Use a Cut stringer
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Deck Design Example 1
 Stair Treads
 DCA 6 Table 6
 Cut stringer
 5/4x6 southern pine
treads
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Deck Design Example 1
 Guard requirements
 Deck height < 30″
 Guard optional
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Deck Design Ex. #1 ‐ Framing Plan
Southern Pine
2
8
0
0
18
500
8
8
N/A
N/A
N/A
2
17
15
15
6
5/4
2’
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6
48
8
8
0
6
2’
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Deck Design Example 2
Deck
House
Beam
 Deck height = 8'-0"
 16' x 20' deck surface
 Structural members: southern pine
 Decking: 5/4 radius edge southern
pine decking
 Framing around a 5′ wide by 2½′
deep bay window
 48" frost line
Joists
 Determine sizes for joists, beams,
hangers, footings, stringers, and
treads
 Determine fastener spacing for
bolts in 1-1/8″ EWP house rim board
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Deck Design Example 2
 Joist Size for 16′ span dimension
 DCA 6 Table 2
 2x10 @ 16″ o.c.
 Cantilever = LJ/4
• 14′-0″ /4 = 3′-6″
• 14′ + 3′-6″ =17′-6″ > 16’ OK
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Deck Design Example 2
 Beam Size for
20′ span
dimension
DCA 6 Table 3
For 14′ joist span
2-2x12 spans 8′-0″
6x6 posts @ 8′ o.c.
LB/4 = 8′/4 = 2′
overhangs
 8′ + 8′ + 2′ + 2′ = 20′
OK





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Deck Design Example 2
 Joist Hanger Size
 DCA 6 Table 3A
 For 2x10
 600 lb joist hanger
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Deck Design Example 2
 Footing Size





DCA 6 Table 4
Thickness = 8″
Square = 18″
Round = 20″
Below frost line
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Deck Design Example 2
 Ledger Fastener Spacing




Assume 1-1/8″ EWP house rim board
Assume 2x10 southern pine ledger
DCA 6 Table 5
½″ bolts @ 12″ o.c.
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Deck Design Example 2
 Stair Stringers
 DCA 6 Figure 28
 8′ deck height
 Requires 10′-4″ stringer span
assuming 7-3/4″ rise and 10″ run
13’3” > 10’-4” solid stringer
 Use solid stringer
 Note: cut stringers could be
used with intermediate support
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Deck Design Example 2
 Stair Treads
 DCA 6 Table 6
 Solid stringer
 2x8 southern pine treads
 Note 5/4 treads could be
used if a cut stringer is
included between solid
stringers
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Deck Design Example 2
 Bay Window




Header = 6′
a = 2’-6”
Double trimmer joist
Trimmer hanger = 1,400 lbs
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Deck Design Example 2
 Lateral attachment
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Deck Design Ex. #2 ‐ Framing Plan
Southern Pine
1-1/8” house rim
2
2’6”
10
0
12
14
600
1400
2’
10
2 10
2’
20
18
18
8
8’
2
12
10
2’
48
8’
8
4
2
8
0
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Deck Design Example 3
Beam
Deck
Beam
 Deck height = 14'-0"
 24' x 30' deck surface
 Structural members: southern pine
 Decking: 5/4 radius edge southern
pine decking
 Framing around a 8′ wide by 3′ deep
bay window
 48" frost line
House
Joists
 Determine sizes for joists, beams,
hangers, footings, stringers, and
treads
 Determine fastener spacing for bolts
in southern pine house rim board
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Deck Design Example 3
 Joist Size for 24′ span
dimension
 DCA 6 Table 2
 2x12 @ 12″ o.c.
 Cantilever = LJ/4
• 18′ /4 = 4′-6″
• 18′ + 4′-6″ = 22′-6″ < 24’ NG
 Cantilever both ends
• Free-standing deck
• 18′ + 3′ + 3′ = 24’ or
• 16′ + 4′ + 4′ = 24’
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Deck Design Example 3
 Beam Size for 30′ span dimension




DCA 6 Table 3
For 18′ joist span
3-2x12 spans 8′-10″
6x6 posts @ 8′ o.c.
Copyright © 2013 American Wood Council
Copyright © 2013 American Wood Council
- LJ/4 = 2′-2.5″
- 3(8′-10″) + 2(2′-2.5″) = 30′-11″ OK
- Use 1′-9″ overhangs each end
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Deck Design Example 3
 Joist Hanger Size
 DCA 6 Table 3A
 For 2x12
 700 lb joist hanger
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Deck Design Example 3
 Footing Size





DCA 6 Table 4
Thickness = 10″
Square = 23″
Round = 25″
Below frost line
 Since deck height
is 14′, footing top
needs to be at
ground level (see
Figure 22)
 48″ tall caisson
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Deck Design Example 3
 Attachment to house
 Free-standing deck
 DCA 6 Figure 23
 ½″ lag screws @ 16″ o.c. staggered
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Deck Design Example 3
 Stair Stringers
 DCA 6 Figure 28
 14′ deck height
 Requires 18′-4″ stringer
span assuming 7-3/4″
rise and 10″ run
 NG
 Requires intermediate
support
• Landing
• 4x4 posts
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Deck Design Example 3
 Stair Treads
 DCA 6 Table 6
 Solid stringer
 2x8 southern pine
treads
 Note 5/4 treads could
be used if a cut stringer
is included between
solid stringers
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Deck Design Example 3
 Bay Window
 Free-standing deck
 No trimmers or headers needed
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Deck Design Example 3
 Lateral attachment
 Not required for freestanding deck
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Deck Design Ex. #3 ‐ Framing Plan
Southern Pine
3’
3
0
16
See figure 23
700
N/A
12
18
beam
staggered
3’
N/A
N/A
25
23
8’10’’
1’9’’
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Copyright © 2013 American Wood Council
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10
8’10’’
2
48
8’10’’
12
8
10
18 4
supported
Supported
2
8
1’9’’
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Resources
DCA6 Deck Guide
http://www.awc.org/publications/DCA/DCA6/DCA
6-09.pdf
DCA6 Presentation
http://www.awc.org/pdf/DCA6-Decks-webinarAug2013.pdf
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Resources
Forest Products
Society
Wood Design Focus
http://www.forestprod.org/
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Downloads
AWC DCA6 Deck Guide
http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf
AWC DCA6 Presentation
http://www.awc.org/pdf/DCA6-Decks-webinar-Aug2013.pdf
AWC DCA6 One-Pager to Post to Website
http://www.awc.org/pdf/DCA6-ResidentialDeckGuide-1009onepager.pdf
Forest Products Society - Wood Design Focus
http://www.forestprod.org
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Questions
?
www.awc.org
info@awc.org
202-463-2766
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