The Vibro-Curb has integral, vibration-dampening spring isolators that provide mounting for rooftop HVAC units. Roofing may be completed at a later date without disturbing the unit, which eliminates extra crane or helicopter expenses. A wood nailer is provided for attaching roofing felts. The flexible 9-inch counter flashing provides a weather seal while permitting easy access to the isolators. Roofing around spring access ports is not required with the Vibro-Curb. A minimum of 90 percent isolation efficiency is achieved with the isolators. They may be customized to accommodate the rooftop unit’s weight and center of gravity for optimum vibration dampening. Deflections of 1, 2, or 3 inches may be provided, and vertical limit stops eliminate excessive movement caused by wind loads and seismic activity. Units can be fabricated to match a specific roof pitch or configuration.