How to repair sagging ceiling?

[wellz]

Hi,

We have a sagging ceiling at our home, We move here earlier this year and this is an area highlighted on the property inspection as the glue started to fail.  On some area we can see the nails popping out and it's quite similar to this thread (https://www.workshop.bunnings.com.au/t5/Whole-of-House/Do-I-need-glue-to-fix-sagging-ceiling/td-p/15...).

I have a jack that I can use to prop up the ceiling and planning to put screws throughout the ceiling.  One thing I'm not sure about it how to identify the location of the joist to make sure I screw into the joist and not on ceiling insulation. 

Thank you for the help. 

[EricL]

Hello @wellz 

One way to track the run of the direction of the nails is to use a Deta Powerful Magnet. This will stick to the heads of the nails and will tell you in what direction the nails are going. Another tool you can use is a Ryobi Stud Finder With AC Detection RYSF5003. By doing some preliminary scanning you'll be able to locate the joist in the ceiling. 

If you need further assistance, please let us know.

Eric

[wellz]

Thanks @EricL! I have tried using stud finder and found it difficult to locate the joist. Will try the magnet. Thank you for the suggestion!