915 WALL ST 2019-09-24 - Laserfiche WebLink

• q Prescriptive Residential Wood Deck Construction Guide-Commentary C3 drifting snow,the criteria in DCA 6 can be wall or floor assembly of wood-frame construction." conservatively applied to a deck with a uniformly Aluminum flashing should not be used if it will be in distributed snow load of 40 psf and a 10 psf dead load, contact with treated lumber. Lumber treated with certain preservatives contain copper and will corrode aluminum 10. Section R507.1 of the IRC states that decks shall be flashing as well as ferrous metals. designed to resist lateral loads and that the design is permitted to be per IRC Section 507.2.3.The IRC 12.IRC R110.1 Use and occupancy states: "No building currently does not state the design lateral loads for decks, or structure shall be used or occupied...until the building but it does provide an approved design,which DCA 6 official has issued a certificate of occupancy..." incorporates. 13. See Commentary for Alternative Methods and 11.IRC R703.8(5) requires attachment of flashing Materials. "...Where exterior porches,decks, or stairs attach to a DECKING REQUIREMENTS The American Lumber Standard Committee(ALSC) Load Conditions—Allowable span analysis includes the Policy for Evaluation of Recommended Spans for Span following two load conditions with load applied on one Rated Decking Products(ALSC Decking Policy) span of a two-span continuous beam: provides a uniform method for assessing span-rated a.Uniform Load- the calculated maximum decking products which are produced from many allowable fiber stress in bending derived from ASTM different species of wood,and graded under several .D2555 and D245,or the In-grade test procedures of different grading standards.This ALSC policy covers ALSC Decking Policy,Annex 1 equals or exceeds specific products classified by size of decking and are the stress induced by a 70 psf uniform load on the • assigned a recommended span of usually 16" or 24". recommended span.The analysis assumes normal This policy is not intended to be used for the assessment load duration. or approval of decking spans in excess of 24".The range b. Point Load—the calculated maximum allowable of current grading rule specifications and species fiber stress in bending derived from ASTM D2555 requires the establishment of a uniform common and D245,or the In-grade test procedures of ALSC analytical procedure for assessing the appropriateness of Decking Policy,Annex 1 equals or exceeds the. these products relative to the recommended spans.This stress induced by a 220 pound point load applied at ALSC policy establishes this uniform analytical the midpoint of one span.The analysis assumes 7- procedure. day load duration. The analysis for maximum span rating assumes the See Commentary for Alternative Methods and following design conditions: Materials for decking materials not covered by the 1. Span—Two-span continuous with load applied to ALSC policy. In addition,alternate decking materials only one span. and/or use of alternate methods of fastening decking to 2. Seasoning—Green use condition assumed to be joists has a critical impact on the resistance of lateral 23% MC or greater. loads. Equivalent strength and stiffness developed by 3. Deflection Limit—Deflection under design loads alternative materials and fastening methods is important using calculated average allowable modulus of to ensure adequate lateral capacity. elasticity shall not exceed L/180. JOIST SIZE The format of Table 2 changed in the 2012 version.An Span calculations in Table 2 assume a 40 psf live load, allowable simple span is given,and then an allowable 10 psf dead load, L/360 deflection limit for simple spans, overhang for that span is calculated.The calculated No. 2 grade lumber, and wet service conditions. allowable overhang is limited by the governing bending Overhang(cantilevers)calculations assume L/180 moment,deflection caused by the 220 lb point load, or cantilever deflection with a 220 lb point load(same as by a maximum cantilever span of one fourth of the back used for span rated decking),No. 2 grade lumber,and span(L/4).The 220 lb point load always produces a wet service conditions. larger moment and deflection than the uniform oa a. IK-?' 04. S American Wood Council Aer