ADOPTS WITH AMENDMENTS:

International Residential Code 2009 (IRC 2009)

Heads up: There are no amended sections in this chapter.

Appendix M Wood Decks

AMENDMENT
This section has been amended at the state or city level.
This appendix is a North Carolina addition to the 2009 International Residential Code.
(The provisions contained in this appendix are adopted as part of this code.)

Section AM101 General

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AM101.1 General

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A deck is an exposed exterior wood floor structure which may be attached to the structure or freestanding. Roofed porches (open or screened-in) may be constructed using these provisions.

AM101.2 Deck Design

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This section has been amended at the state or city level.
Computer deck design programs may be accepted by the code enforcement official.

Section AM102 Footers

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AM102.1 Footers

AMENDMENT
This section has been amended at the state or city level.
Support post shall be supported by a minimum footing per Figure AM102 and Table AM102.1. Minimum footing depth shall be 12-inches below finished grade per Section R403.1.4. Tributary area is calculated per Figure AM102.1.
FIGURE AM102

Note: Tributary area of shaded section on free standing deck shown is 5' x 6' = 30 sq. ft. Code will require a minimum footer of 8" x 16" per Table AM102.1.
FIGURE AM102.1


TABLE AM102.1
FOOTING TABLEa,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
For SI: 1 inch = 25.4 mm, 1 square foot = 0.0929 m2.
  1. Footing values are based on single floor and roof loads
  2. Support post must rest in center 1/3 of footer
  3. Top of footer shall be level for full bearing support of post

Section AM103 Flashing

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AM103.1 Flashing

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This section has been amended at the state or city level.
When attached to a structure, the structure to which attached shall have a treated wood band for the length of the deck, or corrosion-resistant flashing shall be used to prevent moisture from coming in contact with the untreated framing of the structure. Aluminum flashing shall not be used in conjunction with deck construction. The deck band and the structure band shall be constructed in contact with each other except on brick veneer structures and where plywood sheathing is required and properly flashed. Siding shall not be installed between the structure and the deck band. If attached to a brick structure, neither the flashing nor a treated band for brick structure is required. In addition, the treated deckband shall be constructed in contact with the brick veneer. Flashing shall be installed per Figure AM103.

FIGURE AM103

Section AM104 Deck Attachment

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AM104.1 Deck Attachment

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When a deck is supported at the structure by attaching the deck to the structure, the following attachment schedules shall apply for attaching the deck band to the structure.

AM104.1.1 All Structures Except Brick Veneer Structures

AMENDMENT
This section has been amended at the state or city level.
METHOD FASTENERS 8' MAX
JOIST
SPANa
16' MAX
JOIST
SPANa
1 5/8" Hot dipped galv. bolts with nut and washerb
and
12d Common hot dipped galv. nailsc
1 @ 3'-6" o.c.
and
2 @ 8" o.c.
1 @ 1'-8" o.c.
and
3 @ 6" o.c.
OR
2 Self-drilling screw fastenerd 12" o.c staggered 6" o.c staggered
  1. Attachment interpolation between 8 foot and 16 foot joists span is allowed.
  2. Minimum edge distance for bolts is 21/2 inches.
  3. Nails must penetrate the supporting structure band a minimum of 11/2 inches.
  4. Self-drilling screw fastener shall be an approved screw having a minimum shank diameter of 0.195" and a length long enough to penetrate through the supporting structure band. The structure band shall have a minimum depth of 11/8". Screw shall have an evaluated allowable shear load for Southern Pine to Southern Pine lumber of 250 pounds and shall have a corrosion resistant finish equivalent to hot dipped galvanized. Minimum edge distance for screws is 17/16". A maximum of 1/2" thick wood structural panel is permitted to be located between the deck ledger and the structure band.

AM104.1.2 Brick Veneer Structures

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FASTENERS 8' MAX JOIST SPANa 16' MAX JOIST  SPANa
5/8" Hot dipped galv. bolts with nut and washerb 1@ 2'-4" o.c. 1@ 1'-4" o.c.
  1. Attachment interpolation between 8 foot and 16 foot joist span is allowed.
  2. Minimum edge distance for bolts is 21/2 inches.

AM104.1.3 Masonry Ledge Support

AMENDMENT
This section has been amended at the state or city level.
If the deck band is supported by a minimum of 1/2 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.

AM104.1.4 Other Means of Support

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Joist hangers or other means of attachment may be connected to house band and shall be properly flashed.

Section AM105 Girder Support and Span

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AM105.1 Girder Support and Span

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Girders shall bear directly on support post with post attached at top to prevent lateral displacement or be connected to the side of posts with two 5/8 inch hot dipped galvanized bolts with nut and washer. Girder spans are per Tables R502.5(1) and (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 inches, whichever is greater per Figure AM105.3.

TOP MOUNT/FLUSH
FIGURE AM105

SIDE MOUNT DROPPED GIRDER
FIGURE AM105.1

SPLIT GIRDER DETAIL
FIGURE AM105.2

CANTILEVERED DROPPED GIRDER DETAIL
FIGURE AM105.3

Section AM106 Joist Spans and Cantilevers

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AM106.1 Joist Spans and Cantilevers

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This section has been amended at the state or city level.
Joists spans shall be based upon Table R502.3.1(2) with 40 lbs per sq. ft. live load and 10 lbs per sq. ft. dead load. Floor joists for exterior decks may be cantilevered per Table R502.3.3 (1).

Section AM107 Floor Decking

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AM107.1 Floor Decking

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This section has been amended at the state or city level.
Floor decking shall be No. 2 grade treated Southern Pine or equivalent. The minimum floor decking thickness shall be as follows:

SPACING
DECKING (nominal)
12" o.c 1" S4S
16" o.c. 1" T&G
19.2" o.c. 11/4" S4S
24"-36" o.c. 2" S4S

Section AM108 Post Height

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AM108.1 Post Height

AMENDMENT
This section has been amended at the state or city level.
Maximum height of deck support posts as follows:

Post sizea Max. Post Heightb,c
4x4
6x6
8'-0"
20'-0"
  1. This table is based on No. 2 Southern Pine posts.
  2. From top of footing to bottom of girder.
  3. Decks with post heights exceeding these requirements shall be designed by a registered design professional.

Section AM109 Deck Bracing

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AM109.1 Deck Bracing

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Decks shall be braced to provide lateral stability. The following are acceptable means to provide lateral stability.

AM109.1.1

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This section has been amended at the state or city level.
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

AM109.1.2

AMENDMENT
This section has been amended at the state or city level.
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/double band with one 5/8 inch hot dipped galvanized bolt with nut and washer at both ends of the brace per Figure AM109.1

FIGURE AM109.1

AM109.1.3

AMENDMENT
This section has been amended at the state or city level.
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:

POST SIZE MAXIMUM TRIBUTARY AREA MAXIMUM POST HEIGHT EMBEDMENT DEPTH CONCRETE DIAMETER
4x4 48 SF 4'-0" 2'-6" 1'-0"
6x6 120 SF 6'-0" 3'-6" 1'-8"

FIGURE AM109.2

AM109.1.4

AMENDMENT
This section has been amended at the state or city level.
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.
FIGURE AM109.3

AM109.1.5

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This section has been amended at the state or city level.
For embedment of piles in Coastal Regions, see Chapter 45.

Section AM110 Stairs

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AM110.1 Stairs Shall Be Constructed Per Figure AM110

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Stringer spans shall be no greater than 7 foot span between supports. Spacing between stringers shall be based upon decking material used per AM107.1. Each Stringer shall have minimum 31/2 inches between step cut and back of stringer. If used, suspended headers shall shall be attached with 3/8 inch galvinized bolts with nuts and washers to securely support stringers at the top.

FIGURE AM110

Section AM111 Handrails, Guards and General

AMENDMENT
This section has been amended at the state or city level.

AM111.1 Handrails, Guards and General

AMENDMENT
This section has been amended at the state or city level.
Deck handrails, guards and general construction shall be per Figure AM111.

FIGURE AM111

FIGURE AM112
WALKWAYS OVER DUNES OR BERMS IN OCEAN HAZARD AREAS
For SI: 1 inch = 25.4, 1 foot = 304.8 mm.
*  Posts for walkways over dunes or berms shall be embedded a minimum depth of 4'-0" and post heights shall be limited to 5'-0" above grade for 4 x 4 and 10'-0" above grade for 6 x 6. Walkways or portions of walkways over 4'0" in width shall comply with the requirements of Chapters 45 and 46. Maximum walkway surface height is 30" above grade without guard rails.
**  Walkway stair runs can be greater than 12' without a landing.
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