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C2 Prescriptive Residential Wood Deck Construction Guide-Commentary • Basis intent of the provisions of this code,and that the As stated in the boxed text on the cover of DCA 6, material,method or work offered is,for the purpose provisions and details are based on the International intended,at least the equivalent of that prescribed in this-- Code Council's International Residential Code.The code."While AWC develops design tools and guidelines original version of DCA 6 was based on the 2006 IRC. for wood construction,it is recognized that decks are The current version of DCA 6 is based on the 2012 IRC. built with materials other than wood. Many of these materials undergo scrutiny through a code evaluation Alternative Methods and Materials process such as that promulgated by ICC's Evaluation A key point for users is the statement: "This document is Services.Typically,the result is an Evaluation Service not intended to preclude the use of alternative methods Report(ESR)for the product.The building official is and materials."Further,IRC R104.11 states: "An usually the authority having jurisdiction and makes the alternative material,design or method of construction final decision regarding all construction methods and shall be approved where the building official finds that materials. the proposed design is satisfactory and complies with the MINIMUM REQUIREMENTS and LIMITATIONS include helical(spiral)and annular(ring-shank)nails as 1.This document applies to single level residential wood defined in ASTM F 547. Including the common terms decks only.Multiple level decks will likely have stairs "spiral"and"ring-shank" is important to ensure that create additional concentrated loads that are not availability from lumber yards. Reference design values considered in the joist and beam span tables for DCA 6. for post-frame ring shank nails in accordance with ASTM Non-residential decks or balconies typically require F1667 are provided in the 2012 National Design design by a licensed professional.All decks prescribed Specification®(NDS®)for Wood Construction. in DCA 6 use the primary structure to resist lateral forces per Section R507.2.3 of the IRC. 6.NDS Chapter 11 contains spacing,end,and edge distance requirements for various fasteners,including 2.This ratio is limited to 1.:1,similar to open-front bolts and lag screws. structures defined in Special Design Provisions for Wind and Seisrnic.(SDPWS). Decks covered in this document 7. When subjected to standardized laboratory tests that are assumed to be diaphragms that cantilever from the accelerate the corrosion process,metal connectors and house and are limited to a deck length-to-width ratio of fasteners exposed to the chemicals used in certain 1:1. Larger aspect ratios may be permitted where preservative treatments exhibit high rates of corrosion. calculations show that larger diaphragm deflections can Users should rigorously apply recommendations of the be tolerated. See Deck Framing Plan. chemical manufacturers and the treating industry—to use corrosion resistant fasteners and connectors or zinc 3.DCA 6 provides 6x6 nominal pots as the primary coated(galvanized)fasteners and connectors with prescriptive solution with the alternative to substitute corrosion protection at least equivalent to that of hot-dip 8x8 postsIn some instances, this commentary provides galvanized products.Additional information is available . a 4x4 nominal post alternative. See commentary from various sources including: regarding Table 4. http://awc.orgthelpoutreach/factifacylles/Corrosion. WIT 4,Table 1 does not provide an exhaustive list of preservative treatments for ground contact lumber.The • FEMA TB8-96, Technical Bulletin 8, Corrosion American Wood Protection Association(AWPA) Protection of Metal Connectors in Coastal Areas, promulgates voluntary wood preservation standards. recommends that stainless steel fasteners be used in AWPA Standards are developed by its technical areas exposed to salt water. committees under an ANSI accredited consensus-based process. Note also that many preservative treatments 8. Concentrated loads,such as those created by hot tubs, undergo scrutiny through a code evaluation process such stairs,and planters,are beyond the scope of DCA 6. as that promulgated by ICC's Evaluation.Services. Typically, the result is an Evaluation Service Report 9. Structural members and connections shown in DCA 6 %/ (ESR)for the product. have been sized based primarily on a uniformly distributed floor live load of 40 psf and a dead load of 10 5. Smooth shank nails are prone to"backing out"of psf(table footnotes specify where other point loads have wood due to moisture cycling. Deformed-shank nails been considered).If a deck is not prone to sliding or American Wood Council