Section 304.1/Mechanical Equipment Installation
IMC 304 covers general installation requirements for mechanical equipment including support, vibration isolation, anchorage, clearances to grade, and rooftop mounting.
All mechanical equipment must be installed in accordance with the manufacturer's installation instructions and the requirements of IMC Chapter 3. Section 304.1 requires equipment to be supported on a level base adequate for the weight and vibration of the equipment. Rooftop equipment must be installed on a raised curb or stand at least 3 inches above the roof surface to prevent moisture intrusion and allow roof maintenance. Outdoor ground- mounted equipment must be supported on a concrete pad or other approved base that raises the equipment above the finish grade. Equipment subject to vibration must have vibration isolation mounts to prevent transmission of noise and vibration to the building structure. Seismic bracing is required in seismic design categories C and above per the building code and ASCE 7. Section 304.11 requires equipment to be anchored to resist wind and seismic forces.
Why this section exists
Mechanical equipment operates continuously under dynamic loads from motors, fans, and compressors. Equipment that is inadequately supported or isolated transmits vibration through the building structure, causing noise complaints and potential structural fatigue. Rooftop equipment that sits directly on the roof membrane causes leaks and prevents maintenance access. Equipment that is not anchored for wind and seismic forces can shift, disconnect from piping and ductwork, or fall during severe events. Proper access and service clearances must also be maintained around installed equipment.
What plan reviewers look for
Plan reviewers check rooftop equipment details for curb height (minimum 3 inches above roof), flashing, and structural support. They verify that equipment schedules include weight and that structural drawings show adequate framing for concentrated rooftop loads. For ground-mounted equipment, they check pad details and clearance above grade. In seismic design categories C through F, they verify seismic restraint per ASCE 7 Section 13.3. They check that vibration isolation is specified for equipment above occupied spaces.