R Series Rails are high quality, fully adjustable support systems for rooftop unit vibration isolation and seismic/wind restraint. R Series Rails can be supplied as individual rails in pairs or unitized. R Series Rails are ideal for supporting equipment that does not require a full perimeter curb or ductwork going through the roof. Each custom-built unit incorporates both the rail and spring isolation into one complete structure. VMC engineers design each rail to custom fit any rooftop mechanical equipment. 

R7200 2" deflection spring rails can be specified to compensate for large floor spans, and spring pockets are positioned within the rail at the correct load points for proper support and seismic restraint. All spring pockets incorporate a minimum 1/4" elastomeric cup or pad in series with the spring to provide optimum isolation efficiency. 

Fully flashable rooftop rail support system also saves the contractor unnecessary labor costs.  The rail and rooftop unit can be fully installed and adjusted before the roof is sealed, eliminating the possibility of any damage to a finished roof. 

Leveling of the rooftop unit is accomplished easily as all spring pockets are accessible from around the outside of the rails. All springs are color-coded for ease of identification, and any spring can be removed and replaced with the rooftop unit installed.  Once adjusted and leveled, the rooftop unit becomes free floating - completely isolated from the building structure, while completely restrained to it.  

R Series Rails are fabricated from force-resisting structural steel specifically designed to withstand seismic and high wind forces. Unlike standard curbs that typically come with a  rooftop handling unit, or sheet metal rails incorporating a seismic isolator, the VMC rooftop support systems combine our seismic spring design within a moment resisting frame. Our high strength frame is capable of direct, positive attachment to both the building structure and the roof mounted equipment while each spring pocket provides vibration isolation and both seismic and wind restraint. Standard sheet metal rails that typically come with rooftop equipment are not capable of resisting these forces and do not allow for direct, positive attachment to the roof structure and mechanical equipment. Our high strength frame can be bolted or welded to the roof's structural steel and will not break away during  an earthquake or high wind forces.

Features & Benefits

  • Sound (TAS) control system that attenuates heat and noise
  • Offers a more efficient, quieter, and user-friendly system
  • Works well with all roofing
  • Structural steel construction facilitates positive connection to the building structure
  • National Roofing Contractor Association (NRCA) design compliant


  • HVAC rooftop equipment such as RTU's, fans, air-cooled condensing units and condensing units




The engineers we employ hold the highest industry-recognized credentials in structural analysis, elastomer development and system dynamics.


We are the first ISO accredited PCA ISO-17065, third-party certification body for special seismic certification of non-structural building components and their mounting configurations by the ICC’s International Accreditation Service.

Test & Measurement

We are the only ISO 17025:2005 Accredited Seismic Simulation Test Laboratory with a triaxial shake table owned and operated by California licensed Structural engineers.

Testing Services Update
DCL now offers Nuclear Qualification and Testing services.

In partnership with Greenberry Industrial, we now offer testing services that meet the requirements of ASME NQA-1.

Call for more information.