Swag a pendant light from concrete ceiling in a condo tower: Bad idea?
December 18, 2015 10:11 AM   Subscribe

We live in a high-rise condo in Miami with concrete ceilings/floors. We'd like to swag a pendant light to hang directly above a dining table. This would involve drilling a single hole in the concrete ceiling to install a hook for swagging the light, which weighs approximately 7 lbs. Help me decide whether or not this is a good idea and if I can do it without a hammer drill and with minimal fuss. Let's assume the landlord is ok with this.

First of all, I'm confident there is no plumbing in the location to be drilled, but with the possibility of hitting rebar or electrical conduit, should I just not even attempt this? Secondly, I own a drill (with no hammer setting) and would prefer to use it with a concrete bit rather than rent a hammer drill. Is this also a bad idea? Lastly, what sort of anchor would you recommend using for the hook and how small a hole (depth and diameter) would be feasible?

Perhaps relevant details: The condo tower is built to modern standards and is only about 10 years old. Most ceiling fixtures in our unit are installed in areas where there's suspended drywall. However, this particular ceiling light has a power box embedded flush in the concrete. From looking at the power box of the ceiling light, it appears the concrete slab is at least 5 inches thick. The ceiling is not bare concrete - it has a sort of smoothed knockdown texture applied to it.
posted by theory to Home & Garden (19 answers total)
You will need a hammer drill for this. There are many kinds of screw anchors to choose from: Screw anchors. I like the lead ones for something like you are doing.
posted by Mei's lost sandal at 10:28 AM on December 18, 2015

A concrete bit and a lead anchor are all you need for this task. Get the hook, examine the screw on it, get an anchor that is for that diameter screw, and then a drill for that size anchor. I would use a 1 to 1 1/2 inch anchor.

How far is the power box in the ceiling from where you want to hang your light? Can you attach the light to the box? For instance, get a metal cover plate for the box. Drill a hole through the plate for the hook, and a hole for the wiring, hook up the wiring and then screw the plate to the box.
posted by Midnight Skulker at 10:40 AM on December 18, 2015

You mentioned there is a power box in the ceiling. Can the fixture be hung from this or is it in the wrong place? You can purchase hardware that attaches to the box including a threaded tube the wire can go through, and a hook that screws onto the tube.
posted by Mei's lost sandal at 10:51 AM on December 18, 2015

Maybe a well researched tube of adhesive as well.
posted by Freedomboy at 10:51 AM on December 18, 2015 [1 favorite]

Response by poster: Yes, the light will be attached to the power box with a cover plate. The only thing I want to do is put a hook in the the ceiling about 20 inches away from the box so I can hang the light directly above a table.
posted by theory at 10:52 AM on December 18, 2015

Response by poster: The result I want would look sort of like this. My difficulty is just deciding how best to anchor that hook into concrete and whether I should even risk it.
posted by theory at 11:04 AM on December 18, 2015

If you drill a hole, rent a rotary hammer, not a hammer drill. The hammer drill is slower and takes more force and skill, things you will not have in surplus on a ladder, going up into the ceiling.
posted by flimflam at 11:24 AM on December 18, 2015

I've done this with a hammer drill, and a regular drill for sure is not powerful enough, but flimflam is right. A rotary hammer is probably a better choice.

If you're worried about hitting something within the concrete, see if you can get a hold of the electrical specs (usually attached to the architectural drawings) and see what's going on inside the ceiling where you want to drill. You can probably get these from the landlord, but if not, you can get them from the city -- stuff like this is in the public record, so you just have to go down to the county building and have them pull it for you. Kind of a pain, but better than drilling through something important.
posted by ananci at 12:04 PM on December 18, 2015

Best answer: The other risk to consider when drilling into a concrete slab is that the slab could be post-tensioned concrete. These are very common in high-rise construction in the last 20 years or so, because they allow for flat slabs (simplifying formwork and saving $$) and shallower slabs (allowing the developer to fit more units in the same height, making them more $$) If so, you run the (small but real) risk of damaging one of the stressed tendons, which can fail quite catastrophically.

Not to be a huge doomsayer, but it is probably worth inquiring with your building manager - they will probably tell you that there is a maximum penetration depth that the engineers recommend (1"?). Or they might tell you the slabs are not PT. But in the rare chance that something goes wrong, you really want to be able to explain that you asked and got information from someone in a position of authority.
posted by misterbrandt at 12:34 PM on December 18, 2015 [3 favorites]

You can absolutely do this with a household drill. You don't need a hammer drill. As Midnight Skulker says, all you need are concrete bit and an anchor. You're hanging a lamp, not anchoring a shelving system. Don't overkill this.
posted by cosmicbandito at 1:26 PM on December 18, 2015

Yep, I'd get it in writing from somebody responsible for the building that it is OK to drill a hole where you want, what depth, how large etc. There is the potential for a seriously expensive problems when drilling into slabs like this.

If you get the go ahead a lead shield will work but I'd use a quick bolt (link to Hilti site but there are generics available at the home improvement Borg near you). Shallower and smaller hole (for 7kgs a 1/4 quick bolt would do using just a 5/16ths hole) and easier to set overhead (hammer it in and it stays). Then you just spin a hickey (threaded hook) on to hang your fixture.

If you drill a hole, rent a rotary hammer, not a hammer drill. "

A rotary hammer is massive overkill for a single shallow hole especially considering you would be working on a ladder and rotary hammers are very heavy. A quality battery powered hammer drill is all you need for such a small hole. I have access to both and would still go with the hammer drill. If you drill through the centre of an aluminum pie plate or paper plate it'll help catch the concrete dust.
posted by Mitheral at 1:28 PM on December 18, 2015 [1 favorite]

Response by poster: I talked to building management and yes indeed, it is post-tensioned concrete. Drilling into it is a big No-No, at least for non-professionals like me who don't have access to the building plans. The light is just going to have to hang where it is.
posted by theory at 1:56 PM on December 18, 2015 [5 favorites]

Plan B: Get a block of wood about 4" x 4" x thick enough for whatever anchor you're using. Attach whatever you're using to hang the light to it. Stick it to the ceiling with construction adhesive. (That stuff is tenacious, seriously.) Let it dry for 24 hours. Hang light; profit.

For bonus points, paint it before gluing (but leave the surface that will face the ceiling unpainted).

Pro tip: It's not going to fall down while the glue is drying. But, put newspapers underneath just in case.

Easy cleanup! Just throw away anything you inadvertently smeared with glue. If a limb, amputate.
posted by sourcequench at 2:53 PM on December 18, 2015 [1 favorite]

I would use an etch, and glue a hook on. With lots of research or the consultation of a professional/actually knowledgable friend or family member.

... This is mostly because I hate drilling into concrete and have bad wrists, though. But it also avoids the structural concrete or wiring issues soundly. 7lbs is nothing. Bicycles and race cars are glued together. It just needs to be done properly, and not even very meticulously.
posted by emptythought at 4:04 PM on December 18, 2015

Rather than a block of wood if the mount is exposed you could glue a solid wood medallion or rosette to the ceiling. You'd want to scrape off the coating to get down to bare concrete.
posted by Mitheral at 4:59 PM on December 18, 2015

Seconding the construction adhesive, the max load will far exceed any lights you could hang on it.
posted by blue_beetle at 7:07 PM on December 18, 2015

Another option would be to gang 2 or 3 command products together and hang it with these.
posted by nickggully at 9:10 PM on December 18, 2015

OK, since you can't drill a hole, here's an out-of-left-field suggestion that might be of interest, depending on how inventive you want to be. (And this is what I would do, but I love projects like this.)

The idea is the center the light over an area away from the box. Here are a few pendant lights that accomplish this. They are very rare and spectacularly expensive. But if you want a project, you might be able to rig something up similar that would be more aesthetically pleasing than draping a cord on a hook.

Sample 1
Sample 2
Sample 3

Armed with the photos, you could go to your local Home Depot or equivalent and have someone help you find the appropriate parts to put something together.

You might even be able to buy a regular table top swing arm lamp and modify to hang from the ceiling.
posted by The Deej at 10:49 PM on December 18, 2015

Could you install anchors in the walls on opposite sides of the room? Then stretch rope or cord between them and suspend the lamp from the middle of the cord. Then you would presumably only need to anchor into the wood studs.
posted by H21 at 7:38 PM on December 19, 2015

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