Electrical Conduit

The Full Picture

Conduit is a raceway, which OSHA defines as an enclosed channel designed expressly for holding wires, cables or busbars. The type chosen depends on where it runs. EMT, electrical metallic tubing, is the thin-wall metal tube common indoors. Rigid metal conduit is heavier and used where more physical protection is needed. PVC is nonmetallic and is typically used underground or embedded in concrete. Flexible and liquidtight types connect to motors and vibrating equipment. Which type goes where is set by the spec and the code.

Conduit appears on the plans in several ways. Power and lighting plans show it as line work with hash marks, home runs and circuit numbers. Underground and site plans show duct banks and routing. Riser diagrams show vertical feeder conduit between floors. The spec section for raceways sets the permitted types by location, minimum sizes and any color or separation rules. Conduit sizing for a feeder or large run often comes from a schedule in the drawings, not from the plan lines.

The takeoff unit is the linear foot, sorted by type and trade size, since a 1/2 in and a 2 in run are priced very differently. Fittings are counted EA: couplings, connectors, elbows where factory bends are used, boxes and bodies. Supports are counted per spacing, and the estimator rounds up. Stick length matters for ordering: EMT is commonly sold in 10 ft lengths, so a run is rounded up to whole sticks. Waste and offsets are an assumption each estimator sets.

Conduit is where underestimates hide. Long vertical runs, offsets around beams, routing that follows walls instead of straight lines, pull boxes on long or bend-heavy runs, and sleeves and firestopping at wall and floor penetrations are all easy to leave out. Check the wiring methods in the spec against the plan too: pricing EMT where the spec calls for rigid, or leaving out seals and expansion fittings, changes the line.