The insulation cutting requirement for a ring-clamp drain specifies tapering the insulation back by at least:

The insulation cutting requirement for a ring-clamp drain specifies tapering the insulation back by at least:

• A. 12 inches
• B. 18 inches
• C. 24 inches
• D. 6 inches

Answer: (B)

When a roof uses a ring-clamp drain, the insulation around the drain must be tapered back so there’s a clear, accessible area for the drain assembly and the flashing to be properly terminated. The specified distance of eighteen inches gives enough space to install the drain boot or flashing and to seal the membrane around the drain without the insulation crowding the clamping ring. This creates a clean transition from insulation to drain and ensures a watertight connection, since the flashing can be applied with proper laps and sealant and there’s no insulation under pressure against the ring that could cause gaps or leaks. If the insulation isn’t cut back far enough, there isn’t adequate room to flash and seal around the drain, increasing the risk of water intrusion. Keeping roughly that eighteen-inch taper balances effective flashing space with reasonable insulation usage.

When a roof uses a ring-clamp drain, the insulation around the drain must be tapered back so there’s a clear, accessible area for the drain assembly and the flashing to be properly terminated. The specified distance of eighteen inches gives enough space to install the drain boot or flashing and to seal the membrane around the drain without the insulation crowding the clamping ring. This creates a clean transition from insulation to drain and ensures a watertight connection, since the flashing can be applied with proper laps and sealant and there’s no insulation under pressure against the ring that could cause gaps or leaks. If the insulation isn’t cut back far enough, there isn’t adequate room to flash and seal around the drain, increasing the risk of water intrusion. Keeping roughly that eighteen-inch taper balances effective flashing space with reasonable insulation usage.