EMT across bottom of joists
- Thread starter ChrisFV
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mkgrady
Senior Member
- Location
- Massachusetts
Yes you can. You can go through joists too but you would not need fasteners in that case
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Yes it's permitted you can even run AC or MC cable on the underside of the joists.
Greentagger
Senior Member
- Location
- Texas
- Occupation
- Master Electrician, Electrical Inspector
358.30(B) still requires conduit to at least be securely fastened within 3’ feet of termination point.
The OP is asking about fastening EMT to the bottom of the joist. 358.30(B) refers to EMT installed through the joists.
Carultch
Senior Member
- Location
- Massachusetts
The reason for the 358.30(B) rule is two-fold.
1. The end-user of the building might drive fasteners in the framing members after the walls and ceilings are already finished, unaware of the existence of wiring and plumbing within. The nail guard plates are necessary to protect against this error, if your materials are ever closer than the 1.25" limit of expected embedment.
2. The outermost fibers of the structural members carry the greatest load under bending conditions, and are most important to the structural integrity. Aiming your electrical rough-in for holes for the neutral fibers in the center of the member will have the least impact on the structural performance.
Fastening to the underside of floor joists, outside the context of a finished ceiling immediately below, will not introduce either of these issues. Sure it means fasteners thru the outermost structural fibers, but the hole size introduced by a small fastener is nothing compared to the hole you'd have to drill for EMT or other wiring methods.
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