Both shower and tub wall surrounds can pose a different problem when attempting to locate any studs behind them. While the material itself has one consistent level of density, and is less dense than the wood stud you're trying to locate, the installation of the wall surround includes an air gap between the material and the wall behind it, which interferes with the tool's ability to scan properly.
If your deep-scanning stud finder is not able to find the studs, or if you do not have a stud finder with DeepScan® mode, you may also use a metal detector to locate nail heads. The studs should have a pattern of nails going down each one, which affixes the wallboard to the stud. Look for a series of intermittent metal readings going vertically. If your metal scanner gives you a constant metal reading, you have probably found a metal pipe, not a stud. See this page for more information on scanning for studs with a metal finder.
The more features your stud finder has, the better your chances are of finding studs behind a tub or shower enclosure. Unfortunately, no tool can guarantee that you'll find the studs. There are rare cases where bathroom walls are attached to studs with adhesive, rather than nails or screws, making the studs invisible to metal scanners. If you cannot find studs with either DeepScan® mode or Metal Scan mode, you may have to employ a professional contractor instead of trying to do it yourself.
For troubleshooting tips or questions about which tool is right for your project, please contact us at 1-800-245-9265 Monday through Friday, 8AM - 5PM PST or email techsupport@zircon.com.