Seismic Roof Curbs

[ChuckerD]

As a manufacturer of metal buildings, we provide roof curbs as a building component for framed openings and mechanical units generally based solely on dimensional data. Periodically we are fortunate enough to actually receive the unit model numbers after prodding our customers.

Note: Rarely, if ever, do we see any specifications and/or drawings for a job. All building information is entered onto our own contract forms.

On a recent job our prodding netted us some info that makes me think a "seismic curb" is required. Is there any code-defined requirement for when a "seismic curb" is required, or is this something we will always have to ask our customers (generally a contractor or steel erector)?

 

[JedClampett]

It's unfortunate that you don't receive this kind of information. Our equipment specifications (almost always) include that the structural design for the supporting members is to be done by a licensed engineer and what the criteria is. We then reference two sections in Division 1, one for wind design and one for seismic design.
You might want to call the general contractor and get a copy of the applicable specifications. I've had to transmit this information myself to a curb manufacturer during the submittal review.
Equipment supports are required to be designed per code. I would say a "seismic curb" is required when the seismic loads control over wind. But an engineered curb is always required.