Step 6 · Repair the Wall
With the plumbing confirmed to be leak-free, you can now repair the wall. Cut a piece of cement backer board to perfectly fit the access hole you created. Secure the patch to the wood studs or blocking using corrosion-resistant backer board screws. Apply fiberglass mesh tape to all the seams between the patch and the existing wall. Use a trowel to apply a layer of thin-set mortar over the tape and the entire patch, feathering the edges to make it flush with the surrounding backer board. Allow the mortar to cure fully as per the product's directions before proceeding to tile.