Step 7 · Repair the Wall
Once you are 100% certain there are no leaks, you can repair the wall. You cannot simply re-install the tile you removed, as the new faucet trim (escutcheon) is much smaller than the hole. This is where a 'Remodel Plate' (also called a 'Goof Plate' or 'Smitty Plate') is essential. It's a thin piece of stainless steel or plastic that is larger than your hole but smaller than the new decorative escutcheon will cover. You will install a new piece of moisture-resistant drywall or cement board to patch the majority of the hole, leaving an opening for the valve. Then, apply a waterproof membrane over the patch. The remodel plate is then installed over this, providing a solid, flat surface. Finally, you can tile over the patch and plate, or if using a very large plate, seal it directly to the surrounding tile with 100% silicone caulk.