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Copyright © 2018 American Wood Council 1

Prescriptive Residential Wood Deck Construction Guide with Commentary – DCA 6-2015 IRC Version (BCD 306)Loren Ross P.E.Manager, Engineering ResearchAmerican Wood Council

This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of AWC is

prohibited.

© American Wood Council 2018

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• The American Wood Council is a Registered Provider with the American Institute of Architects Continuing Education Systems (AIA/CES), Provider #50111237.

• Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.

• This course is registered with AIA CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner ofhandling, using, distributing, or dealing in any material or product.

• Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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Hundreds of wood decks get built every year and some without the proper guidance for designing or constructing a safe deck. However, AWC DCA 6, which has been recently updated, includes guidance on provisions for the 2015 International Residential Code (IRC) pertaining to single level residential wood deck construction. Provisions contained in this document that are not included in the IRC are considered good practice recommendations. This webinar will provide an overview of DCA 6 along with its Commentary and Appendices and include several examples showing application of the deck guide.

Course Description

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Upon completion, participants will be better able to:1.Identify deck provision changes from the 2015 IRC

and the corresponding DCA6 along with a refresher on 2012 IRC provisions.

2. Identify minimum prescriptive wood deck requirements

3.Describe deck construction including wood members and fasteners

4.Discuss provisions in DCA6 commentary and provide other resources

Objectives

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1.DCA6 History2.Changes for DCA6-12 and DCA6-153.DCA6 Commentary4.DCA6 Appendixes

Outline

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Polling Question

1. What is your profession?

a) Architect

b) Engineer

c) Code Official

d) Builder/Product Manufacturer

e) Other

Free Downloads

DCA6 Deck Guide with Commentary http://awc.org/pdf/codes-standards/publications/dca/AWC-DCA62015-

DeckGuide-1804.pdf

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Why is this Important?

• Deck & Porch Injury Study www.buildingonline.com/news/pdfs/Outdoor-Deck-and-Porch-Injury-Study.pdf• Nearly 15% of all

deck-related injuries resulted from structural failure

• 60% of structural failures are the deck connection to the house

• 33% are the railing

“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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Cooperators

• 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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Cooperators• Additional Cooperators

• APA-The Engineered Wood Association

• National Association of Home Builders

• Simpson Strong-Tie Company

• Southern Forest Products Association

• Southern Pine Inspection Bureau

• Stairway Manufacturers’ Association

• Virginia Polytechnic Institute and State University

• Washington State University

• NADRA – North American Deck and Railing Association

• WIJMA – Wood I-Joist Manufacturers Association

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Code Basis• Basis and Applicability

• 2015 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 jurisdiction12


Polling Question

2. DCA 6 contains certain good practice recommendations in addition to IRC requirements.

a) Trueb) False

Changes to DCA 6-12 and 15

• Hold-Downs Tension Devices on all Decks• Aspect Ratio 1:1• Post Height based on Tabulated Values• No Hollow Masonry Connection to Ledger• 2x6 Joists Added• I-joist Details for Hold-Down Tension Device• Overhang Tables• Glued Laminated Timber Beams Added• Footing Options Added• Knee Braces

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Decking

• Lumber• American Lumber Standards

Committee (ALSC) approved grade mark

• Naturally durable• Redwood or Western Cedar

• Preservative treated• American Wood Protection

Association (AWPA)• Ground contact

Revised in 201215

Decking• Dimension lumber (2″ nominal)• Span rated decking

• ALSC decking policy• Bear on 3 joists minimum• Substitution

• Approved by building official New to 2012

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Joists

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Polling Question

3. DCA6 defines “span” as…a) clear span, or from inside face of support to inside face of

support. b) engineering span, or from center of bearing to center of

bearing.c) outside span, or from outside face of support to outside face

of support.d) none of the above.


Joists

• DCA 6 Table 2• Allowable overhangs

more clearly defined• New southern pine

design spansNew to 2012

19Max Span is 18’ to maintain

reasonable footing size

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

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2015 IRC

Ledger

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Ledger• Ledger board to foundation wall

• Concrete or solid masonry• ½″ approved anchors

New to 2012

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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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Polling Question

4. Beam splices can only occur at interior post locations.a) Trueb) False


• Spans limited to 18’ due to footer sizes

Beam TableNew to 2012

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Posts• Post-to-Beam

• Notch• 3x or 4x beam• 2-ply beam• Two ½″ diameter bolts w/

washers • Post cap

• 3-ply beams

New to 2012

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Footings• Depth > 12″ or frost line• Soil 1,500 psf bearing capacity

New to 2012

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Footing Sizes and Post Heights

New to 201228


New to 2012: W>L 29

Typical Framing Plan

Lateral Support2015 IRC

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Lateral Support

• Attachment to House• Lateral attachment to

house floor system• 2012 IRC• 2 locations per deck• 1500 lb capacity• Always required

New to 2012

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Lateral SupportNew to 2012

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Lateral Support

New to 2012

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*Non-Ledger Decks are vertically independent of the primary structure but still relyon the primary structure to resist lateral loads. Free-standing decks are bothvertically and laterally independent.

Lateral SupportNew to 2015 IRC

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Diagonal Braces• Decks > 2′ above grade

• require diagonal bracing

• Parallel to beam • Lag Screw to beam and post

• Perpendicular to beam• Bracing not required

New to 2012

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*Diagonal bracing is never installed on center posts

Guards

• Adjacent Fixed Seating Requirement• 36″ measurement from seat

2015 IRC Section R312.1.2 Height.Required guards at open-sided walking surfaces, including stairs, porches, balconies or landings, shall be not less than 36 inches (914 mm) in height as measured vertically above the adjacent walking surface of the line connecting the nosings.

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Guards• IBC/IRC require guard rails

to resist 200 lb concentrated load [Table R301.5]

• Tests require 2.5 safety factor per IBC [1709.3.1]

• 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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Guards – DCA6-12• Guard Post to Rim Joist

• Hold down anchors• Minimum of two ½″ bolts

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1.DCA6 History2.Changes for DCA6-12 and DCA6-153.DCA6 Commentary4.DCA6 Appendixes

Outline

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DCA 6 Commentary• Background information• Example calculations• Alternative provisions

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DCA 6 Commentary

��

�� • Helpful Guidance

• 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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DCA 6 Commentary• Alternate prescriptive provisions

• Ex: 4x4 Posts

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DCA 6 Commentary• Alternate prescriptive provisions

• Ex: Soil Bearing Capacities

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DCA 6 Commentary – Appendix A• Safety glazing provisions

60"

36"

60"

60"

glass in windows within this area adjacent stairs must be safety glazed

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DCA 6 Commentary – Appendix B• Tributary area provisions

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DCA 6 Commentary – Appendix B• Tributary area provisions: Post Height

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DCA 6 Commentary – Appendix B• Tributary area provisions: Footing Size

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Polling Question

4. DCA6 Commentary providesa) background information.b) example calculations.c) alternate provisions.d) all of the above.


Additional Resources

• 2015 National Design Specification® (NDS®) for Wood Construction • Structural lumber

• Design values• 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 cross-section

• 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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Span Calculator• AWC Online Span Calculator

• Simple spans (no cantilever)• Uniform loads• Wet service conditions• Incising factor

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Post Height for DCA 6

• 6x6 minimum• 8x8 Alternate

• DCA 6 Commentary• 14' max. height

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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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Connecting Wood

• Tension perpendicular to grain • Achilles heel of wood connections

initiators:• notches• large diameter

fasteners• hanging loads• shrinkage

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Tension Perpendicular-to-Grain

• NDS Table 11.5.1C• Footnote 2• Restricts loading the

tension zone• Applies to ledgers if

constructed with a single row of fasteners as shown

��

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eCourses

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Resources• Wood Design Focus

• Deck Issue• www.forestprod.org/• Summer 2013

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Downloads

AWC DCA6 Deck Guide www.awc.org/pdf/codes-standards/publications/dca/AWC-

DCA62015-DeckGuide-1804.pdf

AWC DCA6 One-Pager to Post to Websitewww.awc.org/pdf/codes-standards/publications/dca/AWC-

DCA62015-OnePage-1804.pdf

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• This concludes The American Institute of Architects Continuing Education Systems Course

Questions?

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