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I want to install a ceiling fan below an old plaster-and-lathe ceiling. I was thinking of running a piece of wood between two joists in the attic above, then screwing a pancake electrical box directly into that piece of wood.

Rather than cutting into the plaster, I'd simply install the box on the surface of the ceiling (and screw through it to attach the box to the wood above). In other words, the box would not be recessed into the ceiling.

My reason for wanting to do this is that the ceiling is old and not in excellent shape. I worry that if I start cutting into plaster and cutting up lathe between joists, I'll invite more plaster cracks. I'd rather leave the plaster untouched.

I know that you might be able to see the box slightly with this installation method (although I am hopeful that if I get a small enough box and a fan with enough play in the part that covers the box, I can hide everything). I'm not too worried about that, as it should not be very noticeable -- certainly not as noticeable as more cracks in the ceiling.

Are there any other reasons why I couldn't do this?

  • 1
    Use a medallion to hide the box. – Mazura May 10 '18 at 1:00
  • Not an answer, but old plaster brings dangers frin asbestos. Do use PPE, bag your work area to catch all the dust, and seal any cuts/holes by dipping the screw in sealant. – Criggie May 10 '18 at 1:02
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There surface mount boxes that are fan rated.

surface mount box

You can use one of the back knockouts and the proper connector to bring your cable in from above.

Your plan to reinforce with wood above the mounting seems sound. You should not try to mount such a box with just plaster mounted fasteners. You may want to consider steel joist hangers for your crossbeam.

Links images are illustrative only, not an endorsement of brands or sources

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Sure, just get a fan-rated pancake box. They look like any other 8-B pancake box, but have 10/32 screws with reinforced holes. The fan will completely cover it once the canopy cover goes on.

Just take extra care to balance the fan well, as any shaking is likely to crack the plaster. Good fans come with some weights to fine tune them, and usually don't need much adjustment.

You'll still need to notch out for the connector, but your plan sounds like the best route for least disturbance of the plaster, which is definitely preferable.

  • In my case I didn't need to notch for the clamp because I brought the wire in off center. – Jim Stewart May 10 '18 at 4:41
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This is a perfectly acceptable installation method. I used this method 35 years ago to hang three very heavy oil-bath Hunters. Note that if you use the standard pancake box you cannot hang the fan from the box but must have long screws that go into the 2x4 above. The oil bath Hunters of that day were hung from a single heavy central hook which screwed through the central hole in the pancake box into the 2x4 above the ceiling.

Specially designed fan mounting boxes do allow fans to be secured to the box with machine screws but the tabs and threads on the tabs on the standard pancake box are not rated for holding up a fan.

Before you do anything check to see if the mounting bracket for the fan interferes with the pancake box, i.e. will the bracket fit outside the box or inside?

In my case the ceiling was drywall and I did cut a hole in the drywall and mount the 1/2" deep pancake box directly to the cross piece 2x4, but I think surface mounting would work. (One of the three fans was installed in a vaulted ceiling directly into a 2x12 rafter.)

Just be careful to mark the location of the mounting 2x4 so you can go into the center of it from below (since you will not be able to see it from below). One way to do this would be to drill a small hole (or two) into the ceiling from below to mark the spot, then go into the attic and pencil in lines with a 2x4 centered over the hole(s).

Many newer fans (at least the Hunter sealed bearing types) have a bracket which is designed to be secured to the 2x4 above the plaster with special long screws provided. These screws might fit through holes in the pancake box or you might have to drill holes in the metal for them to pass through.

In my case, and I think in yours, it would be best to connect the short 2x4 to the ceiling joists with Simpson Strong Tie corner connectors and use the (short) Simpson screws designed for the purpose to attach the bracket. Hammering nails to connect to the joists could crack the plaster in the ceiling. I cannot remember but I think I used only one corner connector on each end, on opposite sides. I thought two on each end was unnecessary.

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