The floors on this list are ranked from best to worst and grouped in three general categories, Superior, Acceptable, and Inferior. Floors are also ranked from best to worst within each category.
As a general rule, any kind of inorganic material is a better flooring surface in wet areas than organic materials. Organics are those that are derived from living materials. In the case of flooring, this translates to trees (hardwood flooring, engineered wood) and grasses (bamboo flooring).
Carpet is one exception to this rule. Even carpeting made from inorganic materials such as olefin, nylon, or polyester should not be used in wet areas due to its inability to quickly shed water.
One mitigating factor, too: the more engineered the organic project, the hardier it is against moisture. Bamboo, listed below, is a prime example. Though bamboo itself is 100% organic, so many inorganic glues are used in the manufacturing process to laminate the thin stalks of bamboo together that the product becomes more stable when subjected to water.
Floor coverings in the Superior category provide maximum protection against moisture. All of the floor coverings are themselves 100% water resistant. Rank within this category is based on how effectively they protect the substrate from water infiltration. All can be used in kitchens and full bathrooms.
1. Porcelain Tile
Porcelain tile is often used in showers, bathtubs, pools, and other pure-water areas. This material is highly resistant to intense water. Porcelain tile has a water absorption rate of 0.5% or more, as defined by American Society for Testing and Materials (ASTM) C373.
2. Ceramic Tile
As with porcelain, ceramic is superior in areas with water. The only difference is that tile that does use the title of "porcelain" has an ASTM-rated water absorption rate of below 0.5%. The weak point of both porcelain and ceramic is not the tile itself but the grouted seams between the tile.
3. Sheet Vinyl
Sheet vinyl is a 100% waterproof solid surface. Usually it has very few, if any, seams to allow water to penetrate to the substrate.
4. Luxury Vinyl Flooring - Plank
Luxury vinyl comes in long plank strips, typically 7" wide and 48" long. The lock-and-fold style of joinery provides a tight seal against water seeping to substrate.
5. Vinyl Tile
Vinyl tile, like the other resilient floors here--sheet and plank vinyl--is 100% waterproof. However, its multiplicity of seams allow more opportunities for water infiltration below.
Properly sealed concrete is excellent against water. One popular exterior version is to tint and stamp its surface to texture it. It is listed last in this category only because it is rarely used in home interiors.
Floors in the Acceptable category are not made of 100% waterproof material. However, the top surface is waterproof, and when tightly seamed, water can pool on the surface for short periods of time without harm.
1. Engineered Wood
Engineered wood performs better than laminate flooring because its base is of a sturdier, more water resistant plywood base. Engineered wood will not stand up to intense water but it will hold up in a pinch.
2. Laminate Flooring
This artificial product performs better than solid wood flooring in moisture tests. The main issue is that the base of laminate flooring is fiberboard and will blister when water touches it.
3. Linoleum Tile or Sheet
Linoleum is oil-based, making it good against water. However, it is a composite material. Linoleum tile has seams that water can work into.
4. Bamboo Flooring
Though bamboo flooring is made of an organic product, the bamboo is heavily imbued with chemicals and resins that are water-resistant though not waterproof.
Floor coverings in the Inferior category should not be used in wet areas. If installed, you do so at your own risk.
1. Solid Hardwood: Site-Finished
Solid hardwood flooring, particularly of the parquet or tongue-and-groove variety, will not work in below-grade environments such as basements. It is not at all recommended for bathrooms, where water is prevalent. Once hardwood floors become water-logged, it is possible to save them--but they will never be as good as new.
Site-finished hardwood is only slightly better against moisture than pre-finished, since the sealant fills the seams and provides protection against water seeping to the substrate.
2. Solid Hardwood: Pre-Finished
Pre-finished flooring has two sides that can be adversely affected by moisture: top and bottom.
From the top, water can work its way between the seams of pre-finished hardwood flooring to the substrate. Emergency situations (broken pipe, overflowing washer, etc.) may trigger this event or even something as simple as a window left open during a rain storm.
It is simply not a good idea to install carpeting in bathrooms and other wet places. It dries out slowly, promoting mold and mildew growth. Carpeting made from man-made materials such as olefin and polyester would be only minimally better than wool (such as berber carpets) in wet areas. Generally, no matter what type of material the carpeting is made from, do not install it in wet or even semi-wet areas.