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I previously posted a picture from inside my attic showing the spacing of my ceiling joists:

enter image description here

Further to the left of what you see in this picture, I used a magnetic stud finder and marked off the locations (red circles in image) the stud finder hit on painters tape:

enter image description here

It looks like there's 3 rows of locations that the stud finder found, but the spacing between the rows has me confused. The distance between the top row and middle row is 7", while the distance between the middle row and bottom row is 10". Based on the picture of the ceiling joists, my assumption was that spacing between the joists would be 16".

What would explain the clusters of locations the stud finder hit? Are the ceiling joists located exactly in those positions, and empty space is between those clusters?

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  • Magnetic stud finder find metal(mainly steel). Your ceiling joists seems to 16 or 24 inch centres. 7 to 10 inch seem to be the spacing of drywall screws/nails along a joist. Quite possible the person who put up the drywall miss some joists and left the screw in
    – crip659
    Sep 8, 2022 at 20:51
  • @crip659 Based on the locations the stud finder found, where should I drill holes and assume I'll hit a stud?
    – eclipsis
    Sep 8, 2022 at 21:02
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    Draw a straight line between the red circles and drill in between the red circles using a tiny(pin) size bit. Drywall is usually 1/2 inch thick, so should know if you miss. be careful not to go more than about 1/16 inch pass the drywall, you do have cables around.
    – crip659
    Sep 8, 2022 at 21:08
  • Well, that’s button board with plaster, so expect more than 1/2”. But the principle is the same… once the drill bit clears, stop pushing. Sep 8, 2022 at 21:26
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    get a sewing pin ... climb into the attic ... push the sewing pin through the ceiling ... go back downstairs ... find the pin on the ceiling ... that is your reference point
    – jsotola
    Sep 9, 2022 at 0:23

1 Answer 1

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If there is wood (as in lathe) and drywall together, this won't work, but if not, I've had great luck with an electronic stud finder like the one pictured below.

If you google it, go into private browsing (shift, cntrl, P at the same time). Why? Because I googled it a few years ago and later that same day I got an ad on my favorite weather site for dating men. YIKES! Not the way I swing.

electronic stud finder

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  • Private browsing and ad blockers the way to go. Now if I can stop the ads for joining the armed forces. They missed by over four years. The magnetic's are good for finding steel and are cheap.
    – crip659
    Sep 8, 2022 at 21:56
  • Yeah, the magnetic ones are inexpensive, but I prefer the electronic ones because you don't have to find 2 screws (or nails) and start drawing lines. The downside is they only work if you don't have a wood shear wall behind the drywall and the building is new enough not to have lathe and plaster. But if you had a wood shear wall, it would probably suffice for just about anything anyway. Next: I hate some of these ads: A few years ago when I was taking my grand-daughter to school, I had the radio on and many ads for "male enhancement" and ED meds. I always turned it off when they came on. Sep 8, 2022 at 23:22
  • I forgot to mention that some of the stud finders also detect wiring (if the power is on) so as to avoid hitting a cable. Sep 9, 2022 at 16:27

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