P Series Curbs are high quality, structural tubular steel support systems for rooftop unit vibration isolation abatement. Each custom-built unit incorporates both the roof curb and spring isolation into one complete structure. VMC engineers design each curb and rail to custom fit any rooftop mechanical equipment. 

P6300 3" Spring Isolation Curbs can be specified to compensate for large floor spans, and spring pockets are positioned within the curb 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.

These fully flashable rooftop support systems also save the contractor unnecessary labor costs.

The curb and rooftop unit can be fully installed and adjusted before the roof is sealed, eliminating the possibility of any damage to a finished roof.      

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

Features & Benefits

  • Upper frame supports equipment while "flating" on spring isolators
  • Factory installed top flashing ensures a weather-tight installation
  • Curb can be manufactured to any height by increasing spring stanchion height
  • Spring pockets are fully adjustable and offer 1" deflection (P6100), 2" deflection (P6200) or 3" deflection (P6300). All pockets are seismically rated to ensure equipment captivity
  • Expanded metal provides backing and attachment location for 2" thick insulation (insulation provided by the roofer)
  • Duct supports installed to match manufacturers dimensions


  • HVAC rooftop equipment such as RTU's and fans




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.