b'T&R Update Engineering Note to Building Owners: Wind Uplift Load Patterns on Steel Roof Deck Rene Dupuis, PhD PE As a buildingyourelying onstructural owner,areyour PUDDLE Y\'lELD-SOUNIFORM PSF engineerrecord to properly design your steel roofDEGK TO .JOISTUPLIFT PER SDI of deck andstructure. He or she needs toMIN. 1/2"ct,PER SDIADHERED MEMEBRANE supporting be aware ofdifferences inuplifl the distinctwind loadfor mechanicallysingly-ply patternsfastened membrane. Ifou are reroofing your existingthat y building hassteel roofneed to getnote Lo a adeck, youthis structural engineer tothe roofyou make suresystem intending toload the arehave installed does notdeck in a manneranticipatedthe time of notatoriginal construction. 1hecontractorfor means roofingis responsible and methods. 1he roofing contractor also needs toFIG. I- UNIFORM VIIINDlJFLIFT LOAD FER SDI inspectdeckcontaminants,looseFOR AS\' HIDE DEG!ING SEGTION thefordirt, debris, materials, andthe roofing visible moisture. However, isqualifieda contractornotasstructural engineer or26.2 PL.F LINE LOAD FROM 1 Y\'llDE 2\' deck designer to checkadequate deckandPUDDLE WELDMEGH. FASTENED fordesign DEGK TO .JOISTMEMBRANE@21.8 PSF attachment.MIN. 1/2"ct,PER SDI LAP SEAM FASTENED Wind LoadsJ_J_i_l__L1-l_tiii t \'lne building code specifies a design wind speed (such yourmeet. as 90 mph) thatbuilding needs toWind uniformdeck. loads applyuplift loads to your roof Cornerare the highest, the roof perimeter loadssees the nextlevel, and the central areayour highestof roofthe lowest. These design loads comea seesfrom code-stipulated reference bookDesign titled Minimum LoadsBuildings and forOther Structures, ASCE-7. have As an example, let\'s assume youa 40-fl buildingExposure Cinamph wind zonetheFIG.2- LINEAR lJPLIFT LOAD ON with90perMEC-H. FASTENED 1 SHEET@ 21.8 FSF FER EXAMPLE 2\' ASCE-7, 2005 edition. The maximum uniform design uplifL loadroofarefollows: for localareasas Corner-54.8uplift by 24.8 psftheandpsfthe perimeter psfincorners6.3inareas. Perimeter- 36.3 psfHow Different Roof Systems Load Roof Decks in Wind Main roof-21.8 psfClassical roofs have the roof membrane adhered tohe insulatinterestprior totion board, whichturnscrew fastened to the steel deck as A note offor your structural engineer:2010, inis the Steel Deck Institute (SDI) design specified that the roofshown inFigure1. deck should withstandof30ofthe a gross upliftpsf. As2010,1heengineer designs the deck span and structuralthickSDI modified this tothe deckberesist the sayshallanchored toness,size, andspacing. Deck panels are typically 3 weldweld required netbutless than uplift force,not30 psf.ft wide and come in different profiles such as wide rib, narrow In the example above, thecode upliftneeded at buildingloadrib, oriate rib. 1heandpan determine intermed profiledeck 90 mphthe corners andexceeds the SDI-specified inperimetersthe gravil)\' load capacity. Regardless ofload, the SDI gravity 30 psfuplift capacity. Therefore, your engineerto deckneedsspecifies a 30 psfuplift capacityIn this gross uniformfor wind. design a correctiveoverloaded in measure because the deck iscase wedealing with uniform gravit)\'s (down) and areload16www.mrca.org- Midwest Roofer'