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