Vinyl
Vinyl flooring is
among the least expensive and 
most
practical for baths because it is waterproof and wear-resistant, and a
plethora of patterns are available, — everything from speckles to faux
marble. Vinyl is cushioned or noncushioned, sheet or individual tiles.
Some patterns are "inlaid," meaning going through the surface,
or wear layer, and others are "rotogravure," which is just
printed on the surface. Thick vinyl, which involves the surface wear
layers, resists scuffs and stains well, but may be dented by dropped
objects. Thinner vinyl with a urethane wear layer maintains its high
gloss look longer than the thicker vinyl.
Vinyl is available in sheet or tile form. Sheet vinyl is sold in 6- and 12-foot wide rolls, which are often wide enough to cover a bathroom floor with no seams. If you do have a seam, seal it with epoxy to keep it waterproof. Vinyl tiles, which are easier for a homeowner to install, don't protect the subfloor as well against water intrusion because of the numerous joints.
When you make your choice, consider that textured surfaces hide dents better than slick ones. And mottled patterns hide dirt far better than solids.
Laminate floors, made to resemble wood, stone or marble, are increasingly popular. The material is scuff- and wear-resistant and relatively easy to install. Decorative laminates are formed from three types of paper, including a melamine resin-saturated paper, fused under high pressure and heat. For laminate flooring in the bathroom, choose a variety constructed with a high-density core board for its superior water-resistance qualities. Also, choose "color-through" construction, which means that the color extends through to the laminate core. If nicked or chipped, which can happen fairly easily, laminates are difficult to repair. Their practicality as bathroom floors is still debated, due largely to how waterproof they are said to be.
Prefinished wood flooring may be either solid wood or manufactured composites comprised of thin hardwood veneers laid down on plywood or particleboard planks. For a bathroom, the risk of getting plywood or particle-board wet, causing irreversible swelling and distortion, makes them impractical.
Hardwood floors, surprisingly enough, should not be ruled out for bathroom installation. Admittedly, it would be unusual, but the romantic warmth of hardwood floors, properly waterproofed, may apply to a luxurious bathroom as well as the living room. Installation, however, is a major consideration. Both flooring and labor are expensive. Also, the flooring must be placed in your house for about two weeks to allow it to adjust to the humidity levels there. Installation includes sanding, staining and three finish coats. Finish coats should be polyurethane, which will waterproof the flooring without altering the appearance.
Ceramic tiles, and increasingly stone tiles, provide strikingly beautiful – and practical – bathroom flooring. Ceramic tiles are long-wearing, and the varied patterns, styles, and sizes will meet everyone's needs. Glazed tiles can be slippery when wet and should be treated with an anti-slip finish for bathroom floors. Stone tiles include marble, slate, limestone and granite and provide a particularly elegant feel to any bathroom. Marble, however, is not a recommended flooring choice because it is soft and will stain and scratch rather easily. Moreover, it is very slick when wet unless you specify nonskid surfacing. Small mosaic tiles were long a top bathroom floor choice because they are impervious to water, the grout lines are small, and they are more slip-resistant than other tiles.
For ceramic or stone tile floors, the subflooring is a critical beginning point because it must not flex at all, and it must be waterproof. The subfloor and finish floor also must be planned ahead so that there is no height variation with the adjoining room's floor that may cause a stumble.
Bathroom underlayments for tile floors should be either cement board or troweled-on mortar, known as "mud." Although some will swear that one is much better than the other, there is little quality difference if both are properly installed. Mud, however, does allow the tiler to slope a floor or counter, if necessary. Once the underlayment is down, the tile is laid in mastic or mortar and after it has set up sufficiently, often a day or two later, the grout is applied. Because grout is the weak link in such a flooring, bathroom floor tiles should be laid tightly together to minimize the risk of water invasion. And the grout must be well-sealed.
There's such a wide selection of tile colors, sizes, shapes and patterns that you should allow ample time to consider what will best suit your décor. In smaller bathrooms, avoid high-contrast patterns and grout colors that hold the eye and make the room seem even smaller. If you want to avoid cold feet, consider in-floor radiant heating elements with a timed control to take the chill off.