When you choose a material for your shower walls, the amount of effort you're going to expend keeping it clean is one of the most important considerations, right up there with color and water resistance. Mold and mineral deposits are facts of life in the shower, and porous materials provide places for them to grow. The easiest materials to clean are smooth and have few hiding places for mold spores, but when you use your shower every day, not all materials remain that way indefinitely. Less expensive materials can scratch or crack, so don't forget to add "durable" to the equation.
When they are new, fiberglass and acrylic shower walls are nonporous and featureless, and any mold that grows is easy to wipe off. If you have hard water, your shower walls will tend to turn dingy and yellowed no matter what they're made of, but you can usually correct this easily by using a combination of vinegar and baking soda.
Avoid Silicone Caulk
If you can fit one into your bathroom, a one-piece fiberglass shower stall is probably the easiest of all types of shower surrounds to clean. Acrylic sheets are a poor substitute for an important reason -- the edges must be finished with silicone caulk, and that material is a magnet for mold. Once it develops on the edges of the caulk or behind it, the blackening is virtually impossible to remove without replacing the caulk, and it mars the appearance of the stall, no matter how clean you keep the walls.
Like ceramic tiles, porcelain ones are manufactured from fired clay, but because the clay is finer and the glaze is fired at high temperatures, they are less porous than ceramic, and that makes them better candidates for the inside of the shower. You can keep them mold-free with an occasional treatment with bleach and baking soda, and when it comes to removing mineral deposits, plain old vinegar does the job. Their hardness also makes porcelain tiles one of the most water-resistant of shower stall materials, but any tiled wall has a potential weakness when it comes to cleaning, and that's the material between the tile joints.
Is Grout a Problem?
Technically, grout is a porous material, which means that mold and minerals can collect on it and make cleaning a headache. In one contractor's opinion, though, grout wrongfully gets a bad rap when it comes to cleaning. Properly sealing the grout when installing the tiles reduces its porosity dramatically, and contrary to many expectations, vigorous scrubbing isn't necessary. In fact, according to this contractor, wider grout joints are easier to clean than narrow ones. Despite this assurance, it's best to limit the amount of grout by opting for the largest tiles suitable for your bathroom.
Substitutes for Stone
If you're worried about cleaning, natural stone is wall covering to avoid; granite, marble and other types of stone are all porous and quickly become streaked with mineral deposits. You can get the look of stone without all the cleaning problems by choosing a composite material instead. A variety of products duplicate the look of stone while being completely mold and mildew resistant and, as an added bonus, can be glued directly over your existing shower walls. Many of these products have the same weakness as acrylic panels, though, and that is that you must seal the edges with silicone caulk. Some products come with form-fitting trim pieces that help avoid this problem.