b'TECHNICAL & RESEARCHthe bolt protrusions of the clamping ring (seeplace to prevent debris from entering the drain-notation C in Fig. 4). In other words, the roofpipes.membrane must be visible inside of the clamp-ing ring. ROOF SCUPPERSIt is important to ensure that the drainageAnother very important detail for directing hole cut in the membrane is larger than thewaterflowfromtheroofisthescupperand drainpipe but smaller than the clamping ringoverflow scupper. Figure 5 is a typical scupper bolt protrusions. There should be no cuts ordetail drawing from a roof manufacturer. slicesintothemembranethatextendbackWhen using a metal scupper flange insert, toward or under the bolts and clamping ring.whetheritiscoatedmetal,baremetal(such Suchcutscouldexpandandcreatemoistureas galvanized or stainless steel) or prefinished intrusion issues behind the clamping ring. Ifmetal,thefollowingitemsmustbeincorpo-such cuts are present, the clamping ring shouldrated:beremoved,theroofmembranearoundtheThehorizontalmetaldeckflangeof outsideofthedrainbowlcutaway,andathescuppermustbesupportedby target patch of new roof membrane installedwoodblockingtopreventthemetal per the roof manufacturers specifications. Theflange from buckling or bowing when manufacturers specify that such target patchesfastened.Figure6 shows a scupper be of sufficient size to ensure the heat-weldedwithout flanges, which does not meet seam edges will be located 12 in. (300 mm)the roof manufacturers detailing and (minimum) from the roof drain and overflowspecification requirements.drain clamping rings. Then the butyl masticThewoodblockingshouldbewider andclampingringshouldbereinstalledasthanthemetalflangetoensurethat described previously. the blocking fully supports the metal Field splices must not run though the drainflange.ring or the drain sump, or within 12 in. (300Mostroofmanufacturersrequirea mm) of the compression ring because the mem- butyl-basedmasticsealantinstalled brane tension caused by tightening the com- betweenthebacksideofthemetal pression ring can distort or wrinkle the fieldscupper flange and the membrane wall splices. (See notation D in Fig. 4; also, pleaseflashing around the scupper opening to note that 12 in. (300 mm) is a typical distance;provide a sealed gasketmuch like the fortheproject-specificdistance,seetheroofseal achieved at roof drain compression manufacturersspecifications.)Iffieldseamsrings.orsplicesshouldoccur withinthetolerance area, cut the membrane back and install atarget patchasdescribedpre-viously. Theoverflowdrain collar/dam be at a high-erelevationthanthe primaryroofdrainin accordancewithlocal requirements(notation E in Fig. 4). The height of the overflow collar/dam mustmeettherequire-ments established by the roofdrainagecalcula-tionsforheadofwater for the geographic loca-tion of the project. Duringconstruc-tion,reroofing,orroof-ing operations a tempo-rarystrainercover,as indicated by notation F inFig.4.,shouldbeinFigure 6. Incorrect scupper fabrication (no flange attached). Continued on page 10www.mrca.orgMidwest Roofer 921'