Prescriptive Residential Wood Deck Construction Guide with Commentary DCA IRC Version (BCD 306)

Save this PDF as:
Size: px
Start display at page:

Download "Prescriptive Residential Wood Deck Construction Guide with Commentary DCA IRC Version (BCD 306)"

Transcription

1 Prescriptive Residential Wood Deck Construction Guide with Commentary DCA IRC Version (BCD 306) Loren Ross P.E. Manager, Engineering Research American Wood Council Copyright Materials 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 Copyright 2018 American Wood Council 1

2 The American Wood Council is a Registered Provider with the American Institute of Architects Continuing Education Systems (AIA/CES), Provider # 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 of handling, 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. 3 Course Description 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. 4 Copyright 2018 American Wood Council 2

3 Objectives 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 5 Outline 1.DCA6 History 2.Changes for DCA6-12 and DCA DCA6 Commentary 4.DCA6 Appendixes 6 Copyright 2018 American Wood Council 3

4 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 DeckGuide-1804.pdf 8 Copyright 2018 American Wood Council 4

5 Why is this Important? Deck & Porch Injury Study ews/pdfs/outdoor-deckand-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. 9 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 10 Copyright 2018 American Wood Council 5

6 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 11 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 jurisdiction 12 Copyright 2018 American Wood Council 6

7 Polling Question 2. DCA 6 contains certain good practice recommendations in addition to IRC requirements. a) True b) 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 14 Copyright 2018 American Wood Council 7

8 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 Decking Dimension lumber (2 nominal) Span rated decking ALSC decking policy Bear on 3 joists minimum Substitution Approved by building official New to Copyright 2018 American Wood Council 8

9 Joists 17 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. Copyright 2018 American Wood Council 9

10 Joists DCA 6 Table 2 Allowable overhangs more clearly defined New southern pine design spans New to 2012 Max Span is 18 to maintain reasonable footing size 19 Joists AWC Online Span Calculator Simple spans (no cantilever) Uniform loads Wet service conditions Incising factor 18-0 MAX (DCA 6) Free at Apps not free 20 Copyright 2018 American Wood Council 10

11 Ledger 2015 IRC 21 Ledger Ledger board to foundation wall Concrete or solid masonry ½ approved anchors New to Copyright 2018 American Wood Council 11

12 Beams Spans L/4 maximum overhang Splice over posts Joists cannot be attached to opposite sides of the same beam 23 Polling Question 4. Beam splices can only occur at interior post locations. a) True b) False Copyright 2018 American Wood Council 12

13 Beam Table Spans limited to 18 due to footer sizes New to 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 Copyright 2018 American Wood Council 13

14 Footings Depth > 12 or frost line Soil 1,500 psf bearing capacity New to Footing Sizes and Post Heights New to Copyright 2018 American Wood Council 14

15 Typical Framing Plan New to 2012: W>L 29 Lateral Support 2015 IRC 30 Copyright 2018 American Wood Council 15

16 Lateral Support Attachment to House Lateral attachment to house floor system 2012 IRC 2 locations per deck 1500 lb capacity Always required New to Lateral Support New to Copyright 2018 American Wood Council 16

17 Lateral Support New to 2012 *Non-Ledger Decks are vertically independent of the primary structure but still rely on the primary structure to resist lateral loads. Free-standing decks are both vertically and laterally independent. 33 Lateral Support New to 2015 IRC 34 Copyright 2018 American Wood Council 17

18 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 *Diagonal bracing is never installed on center posts 35 Guards Adjacent Fixed Seating Requirement 36 measurement from seat 2015 IRC Section R 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. 36 Copyright 2018 American Wood Council 18

19 Guards IBC/IRC require guard rails to resist 200 lb concentrated load [Table R301.5] 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. 37 Guards DCA6-12 Guard Post to Rim Joist Hold down anchors Minimum of two ½ bolts 38 Copyright 2018 American Wood Council 19

20 Outline 1.DCA6 History 2.Changes for DCA6-12 and DCA DCA6 Commentary 4.DCA6 Appendixes 39 DCA 6 Commentary Background information Example calculations Alternative provisions 40 Copyright 2018 American Wood Council 20

21 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 41 DCA 6 Commentary Alternate prescriptive provisions Ex: 4x4 Posts 42 Copyright 2018 American Wood Council 21

22 DCA 6 Commentary Alternate prescriptive provisions Ex: Soil Bearing Capacities 43 DCA 6 Commentary Appendix A Safety glazing provisions glass in windows within this area adjacent stairs must be safety glazed 36" 60" 60" 60" 44 Copyright 2018 American Wood Council 22

23 DCA 6 Commentary Appendix B Tributary area provisions 45 DCA 6 Commentary Appendix B Tributary area provisions: Post Height 46 Copyright 2018 American Wood Council 23

24 DCA 6 Commentary Appendix B Tributary area provisions: Footing Size 47 Polling Question 4. DCA6 Commentary provides a) background information. b) example calculations. c) alternate provisions. d) all of the above. Copyright 2018 American Wood Council 24

25 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 49 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 50 Copyright 2018 American Wood Council 25

26 Design Values Design values are assigned to predict strength and stiffness properties to meet engineering design requirements 51 Span Calculator AWC Online Span Calculator Simple spans (no cantilever) Uniform loads Wet service conditions Incising factor 52 Copyright 2018 American Wood Council 26

27 Post Height for DCA 6 6x6 minimum 8x8 Alternate DCA 6 Commentary 14' max. height 53 Column and Beam Design Tables simplify process Wood Structural Design Data (WSDD) Column load tables Beam load tables Requires adjusted design values Free at 54 Copyright 2018 American Wood Council 27

28 Connecting Wood Tension perpendicular to grain Achilles heel of wood connections initiators: notches large diameter fasteners hanging loads shrinkage 55 Tension Perpendicular-to-Grain NDS Table C Footnote 2 Restricts loading the tension zone Applies to ledgers if constructed with a single row of fasteners as shown 56 Copyright 2018 American Wood Council 28

29 ecourses 57 Resources Wood Design Focus Deck Issue Summer Copyright 2018 American Wood Council 29

30 Downloads AWC DCA6 Deck Guide DCA62015-DeckGuide-1804.pdf AWC DCA6 One-Pager to Post to Website DCA62015-OnePage-1804.pdf 59 Questions? This concludes The American Institute of Architects Continuing Education Systems Course 60 Copyright 2018 American Wood Council 30