A: You can pull off the loose tiles with your fingers or with a putty knife, but you’ll probably discover that there is no good place to stop. It makes more sense to plan on doing the job right: Replace all three tiled walls.
If you try to remove several rows of tile and cut away the crumbly greenboard behind them, you’ll probably find that the loose tiles aren’t neatly arranged in rows. You could use a reciprocating multi-tool with a grout-removal blade to cut through the grout in a whole row. You might even be able to cut through those joints and through the greenboard to remove it with the row of tiles attached using a long blade, such as Milwaukee’s grout-removal blade ($37.99 at Ace Hardware). But to seal the joint between the greenboard you’d leave and the strip of cement board that you’d add underneath, you would need an exposed strip of greenboard — with its paper covering intact — at least once inch wide.
There is no easy way to do that. And although removing a strip of tile would minimize mess and cost, the job would still stretch over several days — the same amount of time it would take to do it right.
How to choose the best tile for your home project
You should be able to remove tile and greenboard from all three walls in one day, and maybe even prep for new tiles the same day if you’ve shopped ahead of time for materials, including backer board, fasteners, fiberglass mesh tape and thin-set mortar or another waterproofing filler for joints.
Be smart about what you choose as the backing material for the tile. Greenboard, advertised as a water-resistant type of drywall, has a gypsum core between two sheets of paper, just like regular drywall. The only key difference is that the paper is coated to resist moisture. (And, yes, it’s usually green.)
The coated paper makes it suitable for damp areas, such as ceilings in bathrooms. For years, builders sometimes used it behind tile in a shower, but there were so many failures — just like what you describe — that a responsible builder or remodeler would never use it there these days. Gypsum is like talc. The paper is what holds it together in a sheet. Once moisture gets through, the gypsum powder gets gummy and moldy and cannot be dried out.
Cement board, which comes in 3-by-5-foot sheets, is not that much more difficult to deal with, and moisture doesn’t affect it, so it works well as a base for tile around a tub or shower. For it to work correctly, though, you need to pay attention to all the installation details, including leaving a ¼-inch gap between the bottom edge of the board and the top of the tub, attaching it with the recommended screws at the proper spacing, and sealing seams by covering them with sticky-backed fiberglass mesh tape, then coating that with thin-set mortar or another material recommended by the manufacturer.
Manufacturers also make other waterproof backer boards designed for use behind tile in showers and around tubs. Some are lighter than cement board, but compare warranties. Even if the fine print means you’d probably never collect a cent, they do offer a guide to how much manufacturers believe in the products. Durock cement board comes with a 30-year limited warranty. But Fiberock and Durock glass-mat tile backer board — two other options offered by USG for use in wet environments — each have just 20-year ones.
Assume it will take another day or two to install the tile. Unless the tub is level on all three sides, determine how to establish a level line, and plan to trim tiles around the bottom edge as needed, so you end up with rows that look level. If you have time, install just the lowest row of uncut tiles in a level line one day and wait for those to dry overnight to give yourself a solid base for installing the upper rows and filling in below with trimmed tiles.
White tiles about four inches square go with almost anything and will give a bathroom a clean, fresh look — and they’re cheap, too: 16 cents each at Lowe’s. Be sure to get tiles with lugs on the edges, so you don’t need spacers to create the proper joint width for grout.
Add the grout a day or two after you install the tiles, so the mastic is completely dry first. Three days later, apply sealer to the grout, and use silicone caulk to fill the corner joints and the gap between the bottom edge of the tile and the top of the tub.
Yes, it’s a lot of work. But you won’t need to do it again.
Have a problem in your home? Send questions to firstname.lastname@example.org. Put “How To” in the subject line, tell us where you live and try to include a photo.