For a weatherproof transition between these roof types, implement these critical steps:
Structural Connection:
Install double 2x ledger board on main house with 1/2" galvanized through-bolts (spaced 16" OC)
Use Simpson H1 hurricane ties at rafter connections
Water Management:
Step flashing must extend 12" up pitched roof under shingles
Saddle flashing over flat roof membrane (minimum 24-gauge galvanized)
Slope flat roof 1/4" per foot toward scupper drain
Material Transitions:
Ice/water shield over entire flat roof deck + 3' up pitched roof
EPDM or TPO membrane for flat section with termination bar at pitch transition
Climate Consideration: In freeze-thaw regions, add heating cable in gutter above transition to prevent ice dam formation.
