EMT Support in Drywall Ceiling

[Afullilove]

Good afternoon. I currently have a job adding some light fixtures in the basement of a vary old building. From what I can tell the ceiling is drywall/plaster. I need to run conduit and mount boxes to this ceiling but there is no way to locate framing without tearing something up. I believe my only option will be toggle bolts. Any help or insight would be appreciated, thanks.

 

[tom baker]

Some stud finders will read thru plaster. If there is an existing ceiling box that’s differently, fastened to ad and they would either be 16 or 24 on center. Then I would use a small drillbit to locate the center of the joist using toggle bit in a plaster ceiling could cause a lot of cracking.