I want to install a ceiling fan outside under a porch. I would run new conduit up to the underside of the ceiling joist. The joists are covered by bead board which I could cut away from the joist. I found a box by Garvin, their 54171-FANNBWP. The instructions indicate it can be mounted directly underneath the ceiling joist. It is a fan rated, outdoor rated electrical box. I wanted to get some experienced opinions on whether this would be a problem.enter image description hereenter image description here

  • 2
    If you are running conduit on the surface of a beadboard ceiling, then you might want to just surface mount the fan box. This would put the conduit in the correct position to connect to the box. Just be sure that the screws that hold the box go into the joist and are long enough to go deep enough into the joist. Commented Jul 18, 2020 at 0:07
  • The screws into the joist are the key here and the box in my opinion conduit is easy but a improper box can have lethal issues , can’t remember the year but headlines were something like failed ceiling fan hits woman kills infant , I had kids back then and was licensed may not have always used listed boxes prior to this, now as a great grampa and still working so far always since I read that (no internet back then)+
    – Ed Beal
    Commented Jul 18, 2020 at 1:09
  • Please see the photo of the instructions. I have small kids so I did my best to make sure this would all be correctly done. Box is rated for a 70lb fan or 250lb static load. In terms of screw length any recommendations? I was thinking between 2.5 -4 inch grk screws.
    – Elmo
    Commented Jul 18, 2020 at 1:50
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    The instructions say use lag screws to secure the box to the joist. These are coarse threaded fairly large diameter screws which require predrilling. Use a large enough drill so that the joist doesn't split and drill deep enough for the entire length of the screw. The threads should bite, but the shaft should not force the wood out. I use lubricant to ease threading in. I would use 3.5 inch long 1/4 or 3/8 inch diameter. Commented Jul 18, 2020 at 2:50

1 Answer 1


The only real reason to cut into the ceiling would be if you needed to bring the wires down from inside the ceiling. Since that isn't the case, I would buy some 3" lag bolts with pan heads (something like this) and drive them through the bead board and into the joist.

The reason for the diagram is they want to emphasize the joist part (#2 in the list). Screwing this into bead board only would be a recipe for disaster.

  • If the screws used are true "self drilling" then predrilling may not be necessary. It can't hurt to predrill, but it's an extra step. Commented Jul 18, 2020 at 2:59

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