What are the rules for supporting EMT conduit?
NEC 2023 Article 358.30 gives you two numbers to remember: 3 feet and 10 feet. EMT must be securely fastened within 3 feet of every outlet box, junction box, device box, cabinet, conduit body, or other termination, and supported at intervals not exceeding 10 feet along the run.
The 3 foot rule and its exception
The strap near the box is what inspectors check first. If structural members make it impractical to fasten within 3 feet, 358.30(A) Exception 1 allows the distance to stretch to 5 feet from the termination. That covers the classic case of a box mounted on a bar joist roof deck where there is simply nothing to strap to within 3 feet.
Unbroken lengths and fished runs
Exception 2 covers concealed work in finished buildings: unbroken lengths of EMT fished into existing walls or ceilings where securing is impractical may go unsupported. This is for remodel fishing, not an excuse to skip straps on open framing. Horizontal runs through framing members count as supported per 358.30(B) when the tubing passes through bored or punched holes, with securement still required within 3 feet of terminations.
What counts as securely fastened
One-hole straps, two-hole straps, conduit hangers, threaded rod with strut and pipe clamps, all fine. Drive rings and tie wire are a fight you will lose in most jurisdictions for EMT, and ceiling grid wires are not a support means for raceways; independent support wires with fittings are required in fire-rated and non-rated grid per 300.11. Do not support EMT from the supports of other systems either, so no strapping your pipe to the sprinkler main or the ductwork.
Field notes
Vertical runs follow the same 10 foot spacing. Couplings do not count as support points, and a box is a termination, not a support. On rooftops and exteriors, remember expansion fittings where EMT crosses structural joints or long straight runs in temperature swings per 358.42, because a run strapped dead tight at 10 foot intervals with no expansion relief will buckle or shear its straps in the sun. Stock the right strap size: 1/2 and 3/4 inch two-hole straps cost pennies and a neat, properly strapped run is the first thing an inspector sees from the ladder.