Vibration Isolation Rails and Seismic Curbs

RCS carries Vibration Isolation Rails that are engineered to reduce noise and vibration for roof curb-mounted mechanical equipment, and are air and water tight. 

Vibration Isolation Rails are available in 1” and 2” deflection and are compatible with most roof-supported equipment and standard roof curb systems without modification to the curb base. 

Typical applications include support and isolation packaged roof top HVAC units and other air-handling and refrigeration equipment. Isolation rails can also be used for large exhaust fans and are typically mounted directly on non-isolated roof curb systems. 

Vibration Isolation Rails are available in two styles: 

  • Interlocking Aluminum Extrusion Construction
  • G-90 Galvanized Steel with Neoprene Seal
  • Seismic Curbs are available through RCS. Optional stamped calculations offered as required.



This Seam to Seam style, also referred to as Seam-In curbs, offers the best protection for roof penetrations and actually becomes part of the roof where other curbs penetrate the roof.

This style is required to comply with 20-year roof warranties by many major building manufactures within the metal building industry. The attachment to the rib is typically done with a seam cap provided by RCS. When constructed from 0.080 aluminum RCS offers a standard 20-year workman ship warranty. RCS offers a special version of our TRAC Rail Curb Support System for seam-In curbs. 


Flat Range

Flat Flange with Loose Cell Caps

Flat Flange curbs offer great flexibility for new and retro-fit applications. For roofs with panels out of modulation, loose rib caps and plugs can offer a good option. RCS will not recommend rubber or polypropylene or ABS plastic rib covers as the fasteners can cut into the cap base. RCS offers aluminum rib caps & plugs. 

* RCS will not recommend an over/over installation. If you order an over/over installation you must give special attention to the upper (ridge side) connection. Over time ice and water has the potential to erode the connection on the upper side.


Flat Flange with Fixed Cell Caps

Flat Flange curbs with welded on rib caps and plugs can save the erector valuable installation labor and is cosmetically appealing compared to otherwise loose caps. 

*When using curbs with welded on rib caps and plugs special attention must be given to roof curb sub-framing location. If the roof panels are not in perfect modulation, welded on rib caps and plugs may not be the best choice.


Double Curbs

Double Floating Roof Curb System

Double Curbs are typically used when the roof top unit weight cannot be supported by purlins, and loads must be transferred to the main frames with I-Beams. Roof top unit weight would not allow thermal movement of the Standing Seam Roof System if the units were placed on standard curbs attached to the roof, framed opening or HVAC ductwork requirements are larger than the purlin spacing.