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Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck Basic Deck This tip sheet reflects code requirements of the 2018 International Residential Code (IRC) with Washington State Amendments. Typical Deck This document provides building code information applicable to prescriptive residential wood deck design. You may need to hire a licensed architect or engineer to design a deck where any of the following conditions apply: • The deck serves other than a one- or two-family dwelling building • The deck design includes more than one level • The deck will support a hot tub, spa or other heavy object, including heavy deck covering (such as pavers) • The walking surface is more than 14 feet above grade • The deck ledger is attached to house overhangs, bay windows, bricks, stone, or concrete block • The deck is bearing on ground with a slope greater than 1 foot horizontal for every 1 foot vertical • The deck is self-supporting (not attached to an exterior wall) Idaho State Amendments ---PAGE BREAK--- Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck Deck Construction Notes • Design loading for decks is based on 60 pounds per square feet (PSF) live load, 10 PSF dead load, and 1500 PSF soil-bearing capacity. • The illustrations and information in this tip Sheet may be used for decks whether or not they require a permit. See Tip Sheet 0 for when a permit is required. • All wood must be pressure-treated or naturally resistant to decay. Treat cuts, holes, and notches with end-cut solution. • Fasteners, hangers, nails, etc., must be stainless steel, hot-dipped galvanized, or as specifically required for the specified wood preservative used. The coating weights for zinc-coated fasteners to be in accordance with ASTM A 153. Provide documentation in the field showing the required fastener protection for the wood chosen for your deck. • You may modify any components of this Tip Sheet using accepted engineering practices. Any modifications must be reviewed prior to permit issuance. All attachments must be per manufacturer’s installation instructions. • Visit MyBuildingPermit.com for additional Tip Sheets for stairs, handrails, and notching and boring. 24" ---PAGE BREAK--- Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck When using the tables below, interpolation is allowed, extrapolation is not allowed. Sizing of Structural Elements Maximum Deck Joist Span a,c Joist Size Joist Spacing b (inches) Joist Back Span 12 16 24 4 6 8 10 12 14 16 18 Allowable Joist Span Maximum Cantilever (feet-inches) Adjacent Joist Span (feet) 2x6 7-11 7-1 5-9 1-0 1-6 NP NP NP NP NP NP 2x8 10-5 9-5 7-8 1-0 1-6 2-0 2-1 NP NP NP NP 2x10 13-3 11-6 9-5 1-0 1-6 2-0 2-6 2-8 NP NP NP 2x12 15-5 13-4 10-11 1-0 1-6 2-0 2-6 3-0 3-3 NP NP a. Includes Incising Factor. b. When using composite decking, refer to manufacturer’s installation instructions for maximum spacing of joists. c. Spans based on Doug Fir-Larch, Hem Fir and Spruce-Pine-Fir, No. 2 grade, wet service factor. Minimum Beam Size Beam Size c,d,e Deck Joist Span (feet) 6 8 10 12 14 16 18 Maximum Beam Span a,b,d (feet-inches) 4x6 5-2 4-6 4-0 3-5 3-1 2-10 2-7 4x8 6-11 6-0 5-3 4-7 4-1 3-8 3-5 4x10 8-5 7-4 6-6 5-10 5-2 4-9 4-5 4x12 9-10 8-6 7-7 6-11 6-4 5-9 5-4 6x6 6-6 5-7 5-0 4-7 4-2 3-9 3-5 6x8 8-8 7-6 6-8 6-1 5-6 5-0 4-7 6x10 10-7 9-2 8-2 7-6 6-11 6-4 5-10 6x12 12-4 10-8 9-7 8-9 8-1 7-7 7-1 a. Spans based on Doug Fir-Larch, Hem Fir and Spruce-Pine-Fir, No. 2 grade, wet service factor. b. If 2x built up beams to make 4x or 6x beams, they shall be fastened with two rows of 10d (3-inch × 0.128-inch) nails minimum at 16 inches on center along each edge (507.5) c. Beam depth shall be equal to or greater than the depth of intersecting joist for a flush beam connection. d. Beam cantilevers are limited to the adjacent beam’s span divided by 4. e. Includes incising factor. ---PAGE BREAK--- Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck Post Size c,d Maximum Deck Post Height Tributary Area e 20 40 60 80 100 120 140 160 Maximum Deck Post Height a (feet-inches) 4x4 10-0 10-0 8-7 7-0 5-8 4-1 NP NP 4x6 14-0 13-10 11-1 9-5 8-2 7-3 6-4 5-4 6x6 14-0 14-0 14-0 14-0 14-0 13-3 10-9 6-11 8x8 14-0 14-0 14-0 14-0 14-0 14-0 14-0 14-0 a. Measured from the underside of the beam to top of footing. b. Based on Doug Fir, Hem Fir and Spruce-Pine-Fir, No. 2 grade, wet service factor. c. Notched deck posts shall be sized to accommodate beam size. d. Includes incising factor. e. Area, in square feet, of deck surface supported by post and footing. Footing Size a Tributary Area b Side of Square Footing (inches) Diameter of a Round Footing (inches) Thickness (inches) 5 7 8 6 20 12 14 6 40 18 20 6 60 21 24 8 80 25 28 9 100 28 31 11 120 30 34 12 140 33 37 13 160 35 40 15 a. Footing dimensions shall allow complete bearing of the post. b. Area, in square feet, of deck surface supported by post and footings. ---PAGE BREAK--- Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck Deck Ledger and Connections Deck Ledger Connection to Band Joist Joist Span c (feet) On-Center Spacing of Fasteners (inches) ½-inch diameter lag screw with ½-inch maximum sheathing b,c,e ½-inch diameter bolt with ½-inch maximum sheathing c ½-inch diameter bolt screw with 1-inch maximum sheathing d 6 22 36 35 8 16 31 26 10 13 25 21 12 11 20 17 14 9 17 15 16 8 15 13 18 7 13 11 a. Ledgers shall be flashed in accordance with Section R703.4 to prevent water from contacting the house band joist. b. The tip of the lag screw shall fully extend beyond the inside face of the band joist. c. Sheathing shall be wood structural panel or solid sawn lumber. d. Sheathing shall be permitted to be wood structural panel, gypsum board, fiberboard, lumber, or foam sheathing. Up to 1/2-inch thickness of stacked washers shall be permitted to substitute for up to 1/2-inch of allowable sheathing thickness where combined with wood structural panel or lumber sheathing. e. For on-center spacing of specialized fasteners refer to the manufacturer’s installation instructions. Placement of Lag Screws and Bolts in Ledgers and Band Joists Minimum End and Edge Distance and Spacing Between Rows Top Edge Bottom Edge Ends Row Spacing Ledger a 2 inches d 3/4 inch 2 inches b 1-5/8 inches b Band joist c 3/4 inch 2 inches e 2 inches b 1-5/8 inches b a. Lag screws or bolts must be staggered from the top and bottom along the horizontal run. See figure below. b. Maximum 5 inches. c. For engineered rim joists, the manufacturer's recommendations govern. d. The minimum distance from the bottom row to the top edge of the ledger must be in accordance with figure below. e. 2 inches may be reduced to 3/4-inch when the band joist is directly supported by a mudsill, header, or by double top wall plates. ---PAGE BREAK--- Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck ---PAGE BREAK--- Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck Connections and Fasteners (All fasteners, nails, bolts, screws, and connectors must be corrosion resistant.) Type of Connection: Notes: Manufactured Connectors Follow manufacturer’s instructions Post to Footing Post base is required Post to Footing (High Winds) Consult with jurisdiction about additional uplift loads where wind exposure is greater than Risk Category B Post to Beam Connector is required Ledger to House Framing See information on Sheet 5 and Sheet 6 Joist to Beam or Girder 8d – Toe nailed Blocking or Bridging to Joist 10d – Toe nailed at each end Wooden Deck Boards 8d threaded nails OR No. 8 screws Composite Decking Follow manufacturer’s instructions Post to Beam Connection with Knee Brace (Knee braces are required on posts greater than 4 feet in height.) ---PAGE BREAK--- Construction Tip Sheet 05 January 14, 2022 MyBuildingPermit.com I Basic Deck Guards & Attachment Guards are required when the deck is more than 30 inches above grade.)