b'TECHNICAL & RESEARCH Continued from page 9ThefastenerssecuringthescupperGutter systems and downspouts are anoth- Thegutteranddownspoutsmustbe should be installed through the beader type of high-flow water management systemsized,spaced,andformedtomeet of the butyl mastic to provide compres- incorporated into some thermoplastic roof sys- thedrainagecalculations.Thegutter sion against the butyl mastic and helptems.Figure8showsatypicalgutterdetailshould be designed such that it captures to seal the fastener penetrations. installation. Key considerations for these sys- the water as it flows over the metal edge When using coated metal, the flashingtems include the following: flashing without overshooting the exte-process is simplified because the flashing membrane can be hot-air welded to the scupper.Ifusingbareorprefinished metal, primed and self-adhered flashingswillberequired. There are some slight differenc-es between roof manufacturers requirements:whereassome manufacturersrequireself-ad-hered thermoplastic flashing to be used to strip in the scupper flanges,othermanufacturers allow the use of a hybrid flash-ingdetailusingself-adhered ethylenepropylenedieneter-polymer(EPDM)flashingsto strip in the scupper flanges on a thermoplastic olefin membrane system (Fig. 7).Insidethescupperopening, oncethemembraneflashings have been installed, most roof manufacturerswillrequire insidecornerdetailing.Refer totheindividualmanufactur- Figure 7. Hybrid scupper flashing with self-adhering ethylene propylene diene terpolymer (EPDM) ersrequirementspertainingwhite flashing over a thermoplastic roof system.to warranty coverage limits for field-fabricated cornerdetails versuspremolded corner details.Overflowscup-pers,much likeoverflow drains,shouldbe installed at a high-erelevationon the wall based on drainagecalcula-tion for the specif-icprojectsothat theyonlycollect anddirectwater off the roof when the primary scup-perhasmalfunc-tioned or become clogged.GUTTER AND DOWNSPOUT SYSTEMS Figure 8. Typical gutter edge detail.10www.mrca.orgMidwest Roofer22'