Thanks for the explanation @EricL. Now we know what we're dealing with.

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!

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 start ...

Thank you @MitchellMc ! I understand that Bunnings doesn't do Villaboard cut in-store. So looks like I'll have to cut it myself so it will fit in the ...

Thanks @EricL! Tile underlay sheet is probably the easier option. Can you provide a link to a suitable product? Also how do I cut it to size as well a ...