Question: Can RMC, IMC and EMT be installed in concrete?

Answer: The National Electrical Code (NEC) allows all three products to be installed in concrete, as noted in their respective Articles: (Also see NEC 300.6(A)(3)).

Galvanized RMC Section 344.10 (B) Corrosion Environments. Galvanized steel RMC, elbows, couplings, and fittings “shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.”

IMC Section 342.10 (B) Corrosion Environments. “IMC, elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and judged suitable for the condition.”

EMT Section 358.10 (B) Corrosion Protection. “Ferrous or nonferrous EMT, elbows, couplings, and fittings shall be permitted to be installed in concrete, in direct contact with the earth, or in areas subject to severe corrosive influences where protected by corrosion protection and approved as suitable for the condition.”

Members of the Conduit Committee of the Steel Tube Institute apply a zinc coating to galvanize steel RMC, IMC and EMT. Therefore, these products are “protected by corrosion protection” as the code requires. However, in severe corrosive environments, the designer or AHJ may decide to require additional or supplementary protection. If supplementary corrosion protection is required or desired, it can be provided by a factory-applied PVC coating, paint approved for the purpose, or tape wraps approved for the application.

Where steel conduit/EMT emerges from concrete into soil, we recommend that supplementary corrosion protection is applied a minimum of 4 inches on each side of the point where the conduit or EMT emerges. This link will take you to an individual page from the STI Installation Guide pertaining to concrete installation.

UL Product IQ (https://iq.ulprospector.com/en) contains information relating to limitations or special conditions applying to products listed by UL.

The UL Guide Information states that supplementary corrosion protection is not required on rigid metal conduit and IMC when installed in concrete.

The UL Guide Information states the following for EMT: “Galvanized steel electrical metallic tubing installed in concrete on grade or above generally requires no supplementary corrosion protection. Galvanized steel electrical metallic tubing in concrete slab below grade level may require supplementary corrosion protection.”

Where the concrete slab is installed on grade, it is important that the raceway be placed in between layers of rebar and above the bottom of the slab to ensure full encasement. However, there are structural concerns that must be satisfied. These concerns are related to size of the conduit or tubing to be encased and the thickness of the slab.