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Wood Decks Page 1 Appendix M Wood Decks (Entire section is a NC amended appendix) Section AM101 Section AM103 General Flashing AM101.1 General. A deck is an exposed exterior AM103.1 Flashing. When attached to a structure, wood floor structure which may be attached to the structure to which attached shall have a treated the structure or freestanding. Roofed wood band for the length of the deck, or porches (open or screened-in) may be constructed corrosion-resistant flashing shall be used to using these provisions. prevent moisture from coming in contact with the untreated framing of the structure. Aluminum AM101.2 Deck design. Computer deck design flashing shall not be used in conjunction with deck programs may be accepted by the construction. The deck band and the structure band Code Enforcement Official. shall be constructed in contact with each other except on brick veneer structures and where Section AM102 plywood sheathing is required and properly flashed Footers (when plywood is required, use pressure AM102.1 Footers. Support post shall be preservatively treated plywood). Siding shall not supported by a minimum footing per Figure AM102 be installed between the structure and the deck and Table AM102.1 Minimum footing depth band. If attached to a brick structure, neither shall be 12” below finished grade per R403.1.4. flashing nor a treated band for the brick structure is Tributary area is calculated per Figure AM102.1. required. In addition, the treated deck band shall be constructed in contact with the brick veneer. Flashing shall be installed per Figure AM103. THICKNESS Figure AM102 Table AM102.1 Footing table a, b, c Size (inches) Tributary Area Thickness (inches) A x A B x C (Sq. Ft.) Precast Cast-in-place 8 x 16 8 x 16 36 4” 6” 12 x 12 12 x 12 40 4” 6” 16 x 16 16 x 16 70 8” 8” ---- 16 x 24 100 -- 8” 24 x 24 150 -- 8” a. Footing values are based on single floor and roof loads b. Support post must rest in center 1/3 of footer c. Top of footer shall be level for full bearing support of post 2009 NC Wood Deck Code Page 2 Tributary area of shaded section on free standing deck shown is 5’x6’=30 sq. ft. Code will require a minimum footer of 8”x 16” per Table AM102.1 Figure AM102.1 Figure AM103 Deck Flashing between Flashing shall be between bands for full depth and kick out underneath if siding below. Flashing shall extend underneath siding above a min. 2”. House Treated bands on both the house and deck can be in contact with no flashing Deck House No flashing- treated Section AM104 Deck attachment AM104.1 Deck Attachment. When a deck is AM104.1.2 Brick Veneer Structures supported at the structure by attaching the deck to the structure, the following attachment Fasteners 8’ Max Joist Span a 16’ Max joist Span a 5/8” Hot Dipped Galv. Bolts with Nut and Washer b 1@ 2’-4” o.c. 1@ 1’-4”o.c. schedules shall apply for attaching the deck band to the structure. AM104.1.1 All Structures Except Brick veneer Structures: Fasteners 8’ Max Joist Span a 16’ Max Joist Span a 5/8” Hot Dipped Galv. Bolts with nut and washer b and 12d Common Hot Dipped Galv. Nails c 1 @ 3’-6” o.c. and 2 @ 8” o.c. 1 @ 1’-8” o.c. and 3 @ 6” o.c. AM104.1.3 Masonry Ledge Support If the deck band is supported by a minimum of ½ inch masonry ledge along the foundation wall, 5/8 inch hot dipped galvanized bolts with washers spaced at 48 inches o.c. may be used for support. a. Attachment interpolation between 8’&16’ is allowed b. Minimum edge distance for bolts is 2 ½ inches a. Attachment interpolation between 8’&16’ joists span are allowed AM104.1.4 Other means of support Joist hangers or other means of attachment may be connected to house band and shall be properly flashed b. Minimum edge distance for bolts is 2 ½ inches c. Nails must penetrate the supporting structure band a minimum of 1 ½ inches 2009 NC Wood Deck Code Page 3 Section AM105 Section AM106 AM105.1 Girder Support & Span. Girders M106.1 Joist Spans & Cantilevers. Joists shall bear directly on support post with post spans shall be based upon Table R502.3.1(2) with attached at top to prevent lateral displacement or 40 lbs per sq. ft. live load and 10 lbs per sq. ft. be connected to the side of posts with two 5/8 inch dead load. Floor joists for exterior decks may be hot dipped galvanized bolts with nut and washer. cantilevered per Table R502.3.3 (1). Girder spans are per Table R502.5 (1&2). Girder support may be installed per Figure AM105 for top mount; Figure AM105.1 for side mount and Figure AM105.2 for split girder detail. Girders may also be cantilevered off ends of support post no more than 1 joist spacing or 16” whichever is greater per Figure AM105.3. Figure AM105 Figure AM105.1 Figure AM105.2 Figure AM105.3 2009 NC Wood Deck Code Floor joists Max. 16” girder cantilever at ends or 1 rim/band joist whichever is less Girder can have decorative clip. Clip not to exceed D/4. D=depth of member /4 Cantilevered girder is limited to floor loads only, roof loads prohibited on cantilevered girder application Top of post mounted Girder Cantilevered dropped girder detail Side mount dropped girder 2-5/8” Galv. through bolts with nuts and washer Spacing 2x6 2x8 2x10 2x12 12” 10-9 14-2 18-0 21-9 16” 9-9 12-10 16-1 18-10 19.2” 9-2 12-1 14-8 17-2 24” 8-6 11-0 13-1 15-5 Partial reprint of Table R502.3.1(2) , #2 SYP only joist spans 2x2 ledger strip or joist hanger required Decks less than 48” from grade can use 3-16d toenailed for attachment of wood post. Decks 48” or greater from grade requiring lateral bracing shall be anchored at top of wood posts with approve strap or post brackets Top mount/flush Split girder detail Deck post 2-5/8” bolts with nuts and washers Floor joist max o.c. spacing 16” Connector block at each joist nailed to side of joist with 3-8d nails and face nailed through each girder ply with 2-16d nails. Block must fill gap between girder ply’s Split girder limited to floor loads only and cantilever girder ends allowed per AM105.3 Page 4 Section AM107 AM107.1 Floor Decking. Floor decking shall be No. 2 grade treated Southern Pine or equivalent. The minimum floor decking thickness shall be as follows: J (((9((((()t8438uldksfj Section AM108 AM108.1 Post height. Maximum height of Deck Figure AM109 support posts as follows: Section AM109 AM109.1 Deck bracing. Decks shall be braced to provide lateral stability. The following are acceptable means to provide lateral stability. AM109.1.1. When the deck floor height is less than 4’-0” above finished grade per Figure AM109 and the deck is attached to the structure in accordance with Section AM104, lateral bracing is not required. Figure AM109.1 AM109.1.2. 4x4 wood knee braces may be provided on each column in both directions. The knee braces shall attach to each post at a point not less than 1/3 of the post length from the top of the post, and the braces shall be angled between 45 degrees and 60 degrees from the horizontal. Knee braces shall be bolted to the post and the girder with one 5/8 inch hot dipped galvanized bolt with nut and washer at both ends of the brace per Figure AM109.1 AM109.1.3. For freestanding decks without knee braces or diagonal bracing, lateral stability may be provided by embedding the post in accordance with Figure AM109.2 and the following: Figure AM109.2 Post size a Max. Post Height b,c 4x4 6x6 8’-0” 20’-0” a.This table is based on No. 2 Southern Pine posts. b.From top of footing to bottom of girder c.Decks with post heights exceeding these requirements shall be designed by a registered design professional Joist Spacing Decking (nominal) 12” o.c. 1” S4S 16” o.c. 1” T&G 19.2 o.c. 1-1/4” S4S 24”-36” o.c. 2” S4S Post size Max. Tributary Area Max. Post Height Embedment Depth Concrete Diameter 4x4 48 SF 4’-0” 2’-6” 1’-0” 6x6 120 SF 6’-0” 3’-6” 1’-8” Max post height for 4x4 is 4’ from top of footer, 6’ for 6x6 Freestanding decks requiring bracing shall be installed in both directions off each post Decks attached to structure require diagonal bracing only at outside girder line parallel with structure Attached not less than 1/3 of post length Decks attached to structure can also be braced on exterior girder line with embedment option Braces shall be between 45 and 60 degrees Grade Less than 4’ (decking to grade) and attached to structure no bracing required 2009 NC Wood Deck Code Page 5 AM109.1.4 2x6 diagonal vertical cross bracing may be provided in two perpendicular directions for freestanding decks or parallel to the structure at the exterior column line for attached decks. The 2x6’s shall be attached to the posts with one 5/8 inch hot dipped galvanized bolt with nut and washer at each end of each bracing member per Figure AM109.3. AM109.1.5 For embedment of piles in Coastal Regions, see Chapter 45. Figure AM109.3 Section AM110 AM110.1 Stairs shall be constructed per Figure AM110. Stringer spans shall be no greater than 7’ span between supports. Spacing between stringers shall be based upon decking material used per AM107.1. Each Stringer shall have minimum 3 ―” between step cut and back of stringer. All stringers supported at top on suspended headers shall be attached with 3/8” Galv bolts with nuts and washers. One 5/8” bolt top and bottom end with nut and washer If span between post is greater than 7’ center blocking and 1- 5/8” bolt with nut and washer required Max. spacing between stringers 36”. 3 ―” Min 7’ Max. stringer span between supports Section AM111 AM111.1 Handrails, Guards and General. Deck handrails, guards and general construction shall be per Figure AM111. Figure AM110 Figure AM111 Deck post per AM108 Rail posts cannot exceed 7’ o.c. spacing and shall be attached with 2-3/8” Galv bolts with nut & washer to outer bands. Exterior Girder Clear Spans Deck Width Nominal Lumber Size 2x6 2x8 2x10 2x12 20’ (2ply) 3-11 5-0 6-1 7-1 20’ (3ply) ---- 6-3 7-7 8-10 20’ (4ply) ---- ---- 8-9 10-2 *Partial reproduction of Table R502.5(1) at 30 ground snow load and roof ceiling and 1 clear span floor. Deck width is 20’ or less measured in the direction of joists span. Splices in plys must break over bearing supports. Riser openings. Stairs with a 30” or more vertical rise must have solid risers or opening restricted to prevent a 4” sphere from passing per R311.5.3.3. Stairs treads and risers per R311.5.3.1 (8 ΕΎ” Max riser) & R311.5.3.2 (9” minimum tread depth). Stairways min 36” width per R311.5.1 (rail projections allowed). Stair handrail/Guard. Height between 30”-38” per R311.5.6 & R312.1. Openings on side of stairs requiring guards shall not allow a sphere 4 3/8” to pass per R312.2 exception #2. Footers per Table AM102.1. Minimum base of footers 12” below grade. Guards at a Minimum 36” required per R312.1 with 30” drop and opening limits per R312.2 (4” on vertical pickets, 6” on horizontal and ornamental guard rails), top rail and post to support 200lbs with infill to meet 50lbs per Table R301.5 and footnotes. Decking per AM107 for #2 SYP and attached with 2-8d galv nails at each joist or approved screws. Other materials per mfg installation based upon joists o.c. spacing. Alternate material attached per mfg installation instructions. Attachment to structure based upon all cladding types but brick veneer per AM104.1.1, Brick veneer per AM104.1.2, Masonry ledge per AM104.1.3 or other per AM104.1.4. Lateral Bracing per AM 109. AM109.1.1 height required; AM109.1.2 knee bracing; AM109.1.3 freestanding embedment; AM109.1.4 diagonal bracing; AM109.1.5 Coastal embedment. Floor joist cantilevers allowed per Table R502.3.3(1) 2009 NC Wood Deck Code Page 6 Figure AM111.1
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