I am in the middle of a re-wiring project, part of which requires installing new light switches on the inside of an exterior wall (plaster directly on brick). I will be installing the switch box flush to the wall surface and chasing the wall to install conduit (1/2" EMT).

One of the switches will control an exterior light which will be positioned above the switches on the exterior side of the wall. I imagine accomplishing this by a chase which extends straight above the switch box, then a 90° bend toward the external wall where I will install a surface-mounted box. My concern is the drilling depth required to install this conduit.

From what I can tell, my local code (based on the 2018 IRC) only provides restrictions on "chases and recesses," though these terms are not specifically defined. As I have no horizontal chases or chases wider than 12", I believe the only relevant restriction is the depth (not more than 1/3 wall thickness, corresponding to about 2.75" in my case):

Chases and recesses in masonry walls shall not be deeper than one-third the wall thickness. The maximum length of a horizontal chase or horizontal projection shall not exceed 4 feet (1219 mm) and shall have not less than 8 inches(203 mm) of masonry in back of the chases and recesses and between adjacent chases or recesses and the jambs of openings.Chases and recesses in masonry walls shall be designed and constructed so as not to reduce the required strength or required fire resistance of the wall and shall not be permitted within the required area of a pier. Masonry directly above chases or recesses wider than 12 inches (305 mm) shall be supported on noncombustible lintels.

The bend will have the minimum 4" radius, so over a length of around 2-4", the chase will be deeper than the maximum before transitioning to a hole. I do not see any specific restrictions on holes drilled in masonry wall in my code. Does the 90° bend into the wall to the exterior violate the code restrictions on chase or recess depth? The alternative is to use an intermediate junction box in the interior wall, but it would need to remain accessible and therefore visible (not what I want). I do not believe I can use 90° pull elbow and bury it in the wall at the end.


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