b'Guidance for Steel Roof Deck DesignersConsider the Deck By Mark S. GrahamSDI provides additionalI nNovember2019,theSteelgle-plymembraneroofsystemsshouldreviewtheadequacyof DeckInstitute(SDI)issuedapplywind-upliftloadstoroofsteel roof decks and their under-newguidanceforsteelroofdecksdifferentlythanadheredlying structural supports for their decks that features seam-fastened,ability to resist design wind-uplift guidance for steel roofmechanically attached, single-plymembraneroofsystemsdo.Al- loads attributable to line loading though adhered membrane roof membranes. Although this guid- systemsapplyupliftloadsuni- fromseam-fastenedmembrane ance is directed toward roof deckformly across a roof deck, seam- systems.However,guidanceto deck designers designers,single-plymembranefastened membrane systems resultstructuralengineersregarding manufacturers and suppliers, roofin concentrated line loads alonghow to conduct such a review is system designers and roofing con- the deck. Such line loads can re- not provided.tractors also should be aware ofsultinexcessbendingmomentInJanuary2016(andrevised SDIs latest guidelines. and shear applied to the deck orinApril2016),FMGlobalup-a doubling of uplift loads on spe- dateditsPropertyLossPreven-Previous Guidance cificstructuralsupports(joists)tion Data Sheet 1-29, Roof Deck InMay2009,SDIissuedadepending on the orientation ofSecurementandAbove-Deck positionstatement,Attachmentthe membrane sheets relative toRoofComponents,toaddress ofRoofingMembranestoSteelthe deck flutes and joists. concentrated line-load situations. Deck,indicatingthatseam-fas- SDIsdocumentgoesontoFM 1-29 provides separate uplift design tables for steel roof decks tened, mechanically attached, sin- recommendstructuralengineersin uniformly distributed and con-centratedline-loadconditions. Also, an additional table is pro-videdfor60-ksiorgreateryield strengthsteelroofdecks;FM 1-29sprimarytablesarebased upon33-ksiyieldstrengthsteel roof decks.FM1-29indicatesthatcon-centratedline-loadconditions apply when the distance between rows of roof membrane fasteners is more than half the steel roof decks span.SDIs Latest GuidanceSDIs new guidance is provided in its Technical NoteNo. 7, Me-Commercial and Residential Roofing chanicalAttachmentofSingle-Ply Roofing Membranes to Steel Trinity Roofing Ltd. specializes in a variety of roofing applications and Roof Deck: Implications for Steel waterproofing for residential, commercial and institutional buildings. Deck Design. This document in-dicatesthatwithseam-fastened, Phone: 416-630-9213URL: www.trinitycanada.commechanically attached, single-ply Fax: 416-630-1722 Email: info@trinitycanada.commembrane roof systemsthough 16ONTARIO ROOFING NEWSISSUE 4 2019/2020 THE ONLY SOURCE FOR PROFESSIONAL ICI ROOFING CONTRACTORS IN ONTARIO ORN'