Finding joists in ceiling

Submitted by Stillwater215 t3_10p1iq7 in DIY

Hi folks. I’m looking for a bit of advice.

I’m working on a simple home theater set up, and that involves hanging a projector from the ceiling. Now here’s the problem: I can’t find the joists. I tried using a stud finder, but it wasn’t giving consistent results. Following that, I tried using a magnet to find the screws holding the dry way to the joists, but huge sections of the ceiling are magnetic (still trying to make sense of this one). I’m hoping that someone who has worked on a similar project might have some advice on what else to try. I really don’t want to have to take down any of the drywall if it can be avoided.

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jnp2346 t1_j6ieig2 wrote

A few things, the drywall is probably mounted to metal rails that are attached in a perpendicular manner to the joists. This is very common in multi family building. It helps suppress sound transmission between the floors.

Find the AC register. It will most likely be be attached to a joist. Once you find one, the others will be 16” or 24” away.

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SJBreed t1_j6iisuj wrote

Turn the lights off and hold a flashlight against the ceiling. Shine the light along the ceiling and you will be able to see the subtle texture changes. This should enable you to see the joints between the sheets of drywall, which should correspond with some kind of framing.

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robotzor t1_j6ieaes wrote

Why are huge sections magnetic?

If it is magnetic in lines going all the way across the ceiling: you have drywall hanging on resilient channel. Great for soundproofing! Unlikely you actually have this. These can be used as your stud.

If it is a huge magnetic section about 16" or 24" across and goes along the entire ceiling (measure where the magnet holds and releases): this is a sheet metal joist cavity air return duct for your floor or the floor above. These are done by slapping some sheet metal between joists and calling it a return duct. If you suspect this is the case, measure the distance between where the magnet lets go and the edges are your joists.

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danauns t1_j6hv6uc wrote

How big is the projector?

They aren't very big these days, butterfly style toggle bolts would absolutely hold it up with confidence.

Just be mindful when installing if there is insulation above.

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Stillwater215 OP t1_j6hve8h wrote

It’s not too heavy, but heavy enough that I wouldn’t be comfortable with just drywall anchors. Same with the projector screen.

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danauns t1_j6hx0ip wrote

I wouldn't be comfortable with plug style anchors either.

Butterfly anchors on the other hand are not just adequate, they're ideal. There is 0 movement, shaking or jiggling here either ....once you snug it up tight, it's mounted until you take it down.

The projector screen, depending on size and if it's the kind that rolls up and down - yea, you'd want that into something structural.

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aschmack t1_j6l6tft wrote

I used these to hang both a projector and a projector screen from the ceiling drywall in an apartment back in college. They worked fine.

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NagromYargTrebloc t1_j6i2kc6 wrote

I had the same problem. The ceiling was textured and it was throwing off my stud finder and mechanical magnetic nail locator. I decided to buy a cheap metal detecting probe.... the type that metal detecting enthusiasts use while digging to pinpoint a find. It worked great, finding every nail. I used small round stickers to mark each one.

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drphillovestoparty t1_j6lic33 wrote

One thing I see often with DIY'ers is not knowing that most stud finders need to be calibrated when placed on the surface you want to find framing. Press it against the wall, hold it still, push the button and when you here "beep" then you can move it across. Sometimes you need to calibrate it in a different spot as you can't calibrate it over a stud.

I was just teaching a guy this at work the other day, he was watching me install some cabinets in a classroom and was admiring my Franklin stud finder, saying how his doesn't work. I pulled out my cheap 20 dollar one, and showed him how they need to he calibrated. Most stud finders work fine if you aren't going over plaster, double drywall, or a similar situation.

You could also use toggles of the projector isn't overly heavy. Or toggle a finished board onto the ceiling, round over the edges and paint or stain, then attach projector to that. A few toggles spaced apart over the board should leave nothing to worry about.

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OutinDaBarn t1_j6hykc3 wrote

Go up in the attic and look. Measure between 2, the spacing should be the same. Use the location to measure out to where you want to put the projector. Knowing about where the joist is, use the stud finder or tap on the ceiling and find the more solid sound.

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Stillwater215 OP t1_j6hzbza wrote

Unfortunately I’m in a first floor condo, so no access from above.

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Spazhead247 t1_j6i1yw1 wrote

If you have decent hearing, you can knuckle tap the ceiling and find the studs. Or, you can blue light the ceiling and look for the crests and valleys. The first method is better, obviously

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TheFishBanjo t1_j6i96b9 wrote

Building on this idea.

You have some partial results with your stud finder.

Knock around and see if you can hear where it is very solid. Combine those finding with the stud finder and magnet results. You'll find somewhere that you are 90% confident in.

Then, drill a tiny test hole and see if the drill is still getting resistance past 1/2" depth and comes out with some wood on it.

You can do this! I believe in you!

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ghostridur t1_j6ii86j wrote

1/4-20 toggles and it's done you would have to hang from it to pull it down.

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RuaidhriM t1_j6jd726 wrote

Maybe just do exploration hold 1” apart in a line. Small enough to be easy to patch. An awl is perfect for this.

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WinnieWill t1_j6l033x wrote

Magnet is your best friend

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EvilRobotDevil t1_j6l1vu8 wrote

I hung a ladder on my garage ceiling by using a telescoping magnet on a stick. I was able to lock on to the drywall nails ,thus determining the studs.

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saml01 t1_j6idnva wrote

Is there a light in the room? Yes. Start measuring.

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FabianVG t1_j6jhls7 wrote

You've tried all of the non intrusive methods, now it's time to go old school, get a hammer and nail and start nailing until you hit the first joist, then measure from there.

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wb6vpm t1_j6hvgme wrote

Honestly, if your asking questions like this, call a pro. The last thing you’re gonna want is it to come down on you or someone else.

If your ready to do minor repair work, you can use a small (1/8” or smaller) drill bit to drill into the ceiling every 1/2” or so until you hit the stud.

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Stillwater215 OP t1_j6hvmj3 wrote

I’ve done projects like this before, but I’ve never had this much of a problem finding a joist. I’ve got no problem with patching a few holes, so this could work.

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