Measure the distance from the edge of the wall to the edge of the last full sized tile installed on the row.
Tile over basement wall.
For tiling over tiles in bathroom walls you ll need to set up sheets of waterproof membrane in between the concrete wall and tiles.
Be sure you double check the fit with the paper backing still on.
Subtract 1 4 inch from that measurement to get the necessary tile size.
Installing a tile floor in all or part of your basement lets you have some fun with design while still quickly covering up existing concrete floors.
Place a second uncut tile over top of the open space overlapping the tile you just placed below make sure it is flush with the wall then use the bottom to mark the tile beneath.
Now use shears to cut where you marked and you ll have the perfect size piece for that opening.