General Code-based Exemptions

Exemptions are based on occupancy category, seismic design category and component importance factor.

MEP Components and Distribution Systems

Seismic restraints are not required or need not be “designed” for the following:

* MEP components if:

1. The seismic design category is either A or B.
2. The seismic design category is C and the component importance factor (I_P) is 1.0. and its failure cannot impact the performance of an importance factor 1.5 component.

* Floor mounted MEP components in seismic categories D, E and F, if I_P=1.0 and:

1. Flexible connections are provided between the component and their services.
2. The components are mounted at 4-ft or less above the floor level and weight 400-lbs or less.

* MEP distribution systems weighing 5-lb/ft or less in seismic design categories D, E, and F if I_P=1.0.

In the above situations, “need not be designed” means that attachment using fasteners sized to fit any mounting holes in the equipment can be assumed to be adequate.

Additional Exemptions for Pipe

The exemptions and allowances for pipe can, with careful planning save a lot of time and money. They may also mean the difference between making a profit on a project and breaking even, or worse, losing money.

12-in. rule: seismic restraints are not required for pipe if it is mounted with a non-moment generating swivel type connection and all of the hangers in the run are 12-in. or less in length from the supporting structure; and no damage can occur from the expected swing of the pipe. (Restraints are required on equipment that is hung 12-in. or less from the ceiling because equipment behaves more erratically than piping or duct during a seismic event.)

Seismic restraints are not required:

• In seismic design category D, E or F with a component importance factor of 1.5, for pipes of a nominal size of 1-in. or less.
• In seismic design category D, E or F with a component importance factor of 1.0, for pipes of a nominal size of 3-in. or less.
• In seismic design category C with a component importance factor of 1.5, for pipes of a nominal size of 2-in. or less.

Other pipe exemptions apply to trapeze-supported pipe. See “Seismic exemptions for suspended trapeze supported pipe—IBC 2006/ASCE 7-05 (Summary)” available online from the Vibration Isolation & Seismic Control Manufacturers Association (VISCMA), Seismic Restraint of Hot Piping (www.viscma.com/Seismic_restraint_of_hot_piping.pdf).

Exemptions for HVAC Duct

As with the piping exemptions these exemptions and allowances for HVAC duct, can save a great deal of effort and money with careful planning..

The following exemptions will apply for duct if it's I_P=1.0 and either of the following are met:

1. All of the hangers in a run of duct are 12-in. in length from the top of the duct to the supporting structure and the hangers are detailed to avoid bending of the hanger ad its attachment.
2. The ducts have a cross-sectional area of less than 6-sq ft.

The 2009 IBC code permits exemption for HVAC ducts with an I_P=1.5 and a cross-sectional area of less than 6-sq/ft.

HVAC Duct Allowance

MEP components mounted inline with the duct system and hard connected to the duct on at least one end, weighing 75-lbs or less, may be restrained as though they were part of the duct system.

Electrical Exemptions

2006/2009 IBC code permits exemptions:

Where I_P =1.0:

1. All electrical components.
2. Distribution systems. However, hangers anchored to concrete wedge-type expansion anchors must be used.

Where I_P =1.5:

1. Conduit that is less than 2.5-in. trade-size is exempt.
2. Trapeze assemblies supporting conduit, bus ducts or cable trays that weight 10-lbs/ft or less are exempt.

In both cases above, if the hangers are attached to concrete, wedge-type expansion anchors must be used.

Existing buildings

Seismic restraint for retrofit projects are governed by state requirements. However, as a rule of thumb, it can be assumed that it will be required on the same basis as for new construction. If the seismic load on the building increases by more than 10 percent or the seismic capacity decreases by more than 5 percent, the structure will often need to be reinforced.