I have a specification that references ICC 500 and FEMA 361. Are these the same?

No, they are not the same, but they are both related to the construction of tornado shelters. FEMA 361“Design and Construction Guidance for Community Safe Rooms” is a guidance document, but FEMA does not regulate building construction. ICC 500 “Standard for the Design and Construction of Storm Shelters” is written by the International Code Council® and is referenced in the International Building Code in all Editions since 2009.

How do hurricane resistance ratings work? Are they pass/fail or are their levels like with fire ratings?

Hurricane resistance ratings are expressed in pounds-per-square-foot (PSF) values, and unlike fire ratings, there are no standard increments. In addition to the PSF values, they are either listed with or without “missile” impact ratings. In this instance, a missile refers to a 2 x 4 piece of lumber weighing 9 lbs. that is fired at the door at 35 miles-per-hour. A door assembly must withstand 3 impacts in order to have a missile impact listing. A typical door listing would be expressed as;

  • Design Pressure Rating +75/-65 PSF
  • Large Missile Impact – Yes

This listing indicates that the door assembly is rated for 75 PSF when loaded against the stops of the frame, and 65 PSF when loaded away from the stops of the frame

What level STC door do you suggest for an office building near an airport?

There are many variables that would determine the proper STC value, including the physical proximity of the office building to the airport. To ensure that the specification is properly developed, an acoustic consultant should be engaged to determine the Outdoor / Indoor Transmission Class (OITC) values.

STC ValueRatingDescription
50-60ExcellentLoud sounds heard faintly or not at all
40-50Very GoodLoud speech heard faintly, but not understood
35-40GoodLoud speech heard but hardly intelligible
30-35FairLoud speech understood fairly well
25-30PoorNormal speech understood easily and distinctly
20-25Very PoorLoud speech audible

Do you recommend a specific type of core for acoustical doors?

No, we recommend that the door selection be made on the basis of the STC value that has been specified. Multiple door core types may be capable of achieving the specified value, and can be documented by Certificates available from the manufacturer.