Finding a stud behind ceramic or porcelain tile is more complex than finding those behind gypsum. The biggest reason for this is that tile walls can be thicker than drywall. The more layers you add, the less reliable the stud finder's results will be.
Besides that, the thickness of a ceramic tile wall installation may not be consistent. When the thinset mortar is laid down, it's supposed to be even. But inevitably, high and low areas may develop.
Ceramic or porcelain tile often has different substrate materials than an ordinary drywall stud wall, such as cement board (such as Durock or HardieBacker), tile uncoupling mats, various fasteners, layers of thinset, and possibly even metal studs can all complicate the search. If the tile itself happens to be metal, then magnetic stud finders cannot locate the stud.
Equipment / Tools
Read all the steps carefully to determine which of the following tools you need.
- Painter's tape
- Dielectric Constant Stud Finder
- Magnetic Stud Finder
- Ultra Wide Band Scanner
- Measuring tape
- Handheld drill
- Small drill bits (for pilot holes)
- Long finish nail
- Tile grout (if needed)
Locating a stud behind drywall is easier with the right tools. Most conventional stud finders do a relatively good job of finding studs behind the drywall. Drywall is soft and crumbly, and its thickness is constant. But when confronted with ceramic, porcelain, or stone tile, stud finders aren't always as reliable.
The chief reason you might attach an item directly to the stud is if you are mounting a grab bar or other assistive device. But if you are installing a soap dish or other lightweight item, there is no need to drill holes or find studs. These items are installed on the tile surface with epoxy.
Use a Dielectric Constant Stud Finder
Complicated name aside, a dielectric constant (DC) stud finder is one you may already have on hand. This is the type of stud finder that you slide across a wall until a red light signals that there is a solid mass behind the surface, such as a wooden stud.
Dielectric constant stud finders do a poor job of locating studs behind tile as they are prone to returning a host of false-positives when there is a lot of dense material in the area. It's worth giving it a shot anyway.
Begin by running a strip of painter's tape horizontally across the surface. Above or below the tape, pass the DC stud finder across the tile surface from side to side. Go very slowly.
Whenever there is a positive alert, no matter how weak, mark it on the tape with a pencil. After making multiple marks, you may begin to see a pattern develop. Clusters of pencil marks will indicate the presence of a dense item below, such as a stud.
Use Rare Earth Magnets
Rare earth stud finders are super-sensitive, powerful magnets that you can run across a surface in hopes of detecting a metal fastener underneath. Tile isn't secured by metal fasteners, but its cement board substrate often is.
Magnetic stud finders are highly effective at finding studs behind drywall but far less effective at finding anything under the many layers of tile and tile substrate.
You may be able to detect a fastener if you are patient and slow. It's helpful if the substrate is unusually thin. This is a possibility since tile thinset often fails to extrude through the tiler's float at a uniform thickness.
Try Detective Work
Wall studs tend to be spaced every 16 inches on-center. Starting from the corner of the room, measure off 16 inches, and mark that endpoint. Now you have a rough idea of where a stud is located.
What is On-Center?
On-center is a building term that means that you should measure from the center of one stud to the center of the next stud.
One method of fine-tuning your measurement is by drilling tiny investigative pilot holes. You cannot drill through the tile itself, but you can drill pilot holes through the tile grout. Use small bits to start. After you have drilled the hole, use something thin, like a finish nail, to insert in the hole to feel whether there is a stud back there.
You may have to drill several holes to locate the stud. When the nail meets with consistent resistance, you've found the stud.
After you have located the stud, mark its position with a tag of painter's tape on the tile. Cover up the holes up with a touch of grout.
Use an Ultra Wide Band (UWB) Scanner
For finding a stud behind drywall, a UWB scanner is pricey and excessive. But for thick, dense, or otherwise problematic materials like dry or wet concrete, floor heating ducts, or metal, UWB scanners are indispensable. Instead of searching for metallic fasteners, UWB scanners use radar technology and find studs behind thick tile and other materials with surprising ease.
UWB scanners are powerful enough that at various times since their introduction, the Federal Communications Commission (FCC) has required that operators of UWB scanners register their devices with the Commission.
Borrowing or renting a UWB scanner is certainly an option if you want to have easy work of finding studs behind the tile. However, buying one is another matter; most DIYers don't handle enough large projects to justify the expense of a UWB scanner for their tool shed.