b'TECHNICAL & RESEARCH Continued from page 7this case.All bolts with washers (see notation B in Fig. 4 as required by roof manufacturer spec-ificationsandTheNRCARoofingManual: Membrane Roof Systems 2 ) must be in place and must be tight enough to provide compression of the clamping ring against the butyl mastic, whichensuresalong-termwater-tightseal. Every fastener location on the clamping ring andthreadedholeinthedrainbowlmust receive a new stainless steel bolt. Stainless steel isrecommendedbecauseitislesslikelyto corrode. Much like a wheel on a vehicle, every fastener location must receive a fastener to pro-vide even pressure. A simple test to check the tightness of the drain bolts is to try to spin the washers: if the washer spins, the bolt is not tight.The bolt assembly clamping ring must be securedintothedrainbowl.Itisimportant Figure 4. Example of a roof detail sheet. to ensure that there is no damage to the bolts, threads, or washers and no cracks in the clamp-temperaturedifferencesbetweentheshown in Fig. 4. Butyl-based mastic must being ring, bolts, or washers. All bolt holes in the interior and exterior, resulting in ther- present between the drain bowl flange and thedrain clamping ring must receive a bolt. mal bridging and thermal loss. underside of the roof membrane (see notation AIn reroofing scenarios, it is recommended Thefastenersarealsopenetratingin Fig. 4). The mastic should be visible, oozingthat existing bolts be replaced with new bolts. theunderlyingvaporbarrier,whichoutslightlyfromundertheroofmembraneIt is also recommended that the new bolts and was designed in this assembly to notinside the drain bowl and clamping ring. Therewashers are stainless steel to provide long-term bepenetratedbyfastenersbecauseshould also be a discernable hump of masticperformance. itisinstalledoverthemechanicallyunder the roof membrane adjacent to the exte- Onanyroofingorreroofingproject,the attached substrate board. rior edge of the clamping ring. Lead or metalroofingteamshouldensurethatthedrain drain pans are not recommended and shouldring is not cracked or broken in any way. The DRAIN FLASHINGS not be used with thermoplastic membrane sys- clamping ring must be intact to provide con-Drain flashing should be accomplished astems above the insulation board as shown instantcompressionagainstthebutylmastic. Damagedclampingrings must be replaced. (You may have noticed that I have reit-erated this issue a few times. Ithasbeenmyexperience over the years that there will besituationswheresome-onehasattemptedtoreuse a cracked clamping ring on reroofing projects and leaks occur.) The drain basket should alsobeintactandsecured inplaceintotheclamping ring. This is vital to prevent debris from flowing into the drain and creating a backup or clog. Backups and clogged drains could cause structural overloading of the roof struc-tureduringheavyorpro-longed rain events.Thethermoplasticroof membranemustextendat Figure 5. Standard scupper detail with thermoplastic olefin/polyvinyl chloridecoated metal scupper sleeve. leastin. (13 mm) toward the middle of the bowl past 8 www.mrca.orgMidwest Roofer20'