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fidormula t1_jcz3gft wrote

I have a few thoughts.

For plaster, try a magnetic stud finder instead of an electronic one. With any luck (and luck you will need) your lath is wooden and the magnet will stock on the nails. You need a high powered neodymium magnet, not just a fridge magnet for this. If your magnet sticks everywhere, your lath is made of ferrous metal, and you'll have to use a drill. Stick with a small bit, of course.

Joists aren't 16 to 24 inches apart. They're 16 or 24 inches apart, on center. That was the case even 100 years ago. In some cases, 19.2" is the standard joist spacing. Check those three distances from your first hole.

Your joists could be running the opposite direction of what you'd expect. They normally span the narrowest dimension of the house, but some run the longest length of the house. Try those three distances over the other axis, too.

At that age, there is a good chance that your ceiling joists are nailed to studs. If you can find the studs on opposing walls, the joists should run end to end on the outside of the studs.

Good luck!


clemclem3 t1_jd0rl2m wrote

Good advice. I think it's neodymium not molybdenum. Home Depot has a selection


riverofwords t1_jd2i1pd wrote

Thank you!! I’ll be trying the magnet tonight and will go from there.


allangee t1_jcze5ld wrote

Can you get into the attic and see the joists from above? If so, get a straight rod poking up through your test hole and take measurements from that, and then transfer the same measurements from the rod at ceiling level.


9yr0ld t1_jczfwuv wrote

you have joists 12" apart? I feel there's no way. are you sure that's not just strapping for drywall or something?


Zetor22 t1_jcz2gw8 wrote

probably old post and beam, i had one about the same age, sometimes they didnt always follow what we call code. I tell you what though, my floors were unlevel and slanted, I peeled back the years of renovations and the original beams were square and level. They really knew how to build them, and the true lumber, wow, boards 26inches wide, over an inch thick and 14 ft long.


BourbonNeatt t1_jczeql2 wrote

Magnet has always worked for my 100 year old house with wood and lathe walls. Never used it on the ceiling, but I’d assume it would do the trick there too.


Thud2 t1_jczfi5o wrote

Drill a hole as close to perpendicular to the joist in the plaster next to the joist that you found. Stick a feeler wire in there and push it in until you feel the next joist.


imnottrying t1_jd0nos4 wrote

I had a similar issue and I found using large magnets was the only thing that worked for finding joists. Being that nails from the lathe run up and down the joist, you’ll know if it’s a joist pretty quickly.


Zealousideal_Show107 t1_jd1nm1e wrote

Do you have an attic? I had trouble finding them in part of my house so I went from above. Drilled a tiny hole through the ceiling right next to the joist on each end of the room and stuck a small nail through it.