Solid hardwood floors are available in various sizes, ranging from the very common, 3/4 inch thick by 2 1/4 inch wide plank, to widths of 6 inches. They are also available in numerous different colors and patterns, including the most common, red oak, white oak, and maple. Solid hardwood floors are very sensitive to moisture, so one has to be careful before he or she installs them in a certain location that may be affected by weather changes or changes in moisture in the air. When moisture leaves the wood during dry winters, the hardwood floor will contract in size. In the summertime, when there is more humidity in the air, the hardwood planks will expand and they may overlap one another. Both circumstances do not produce welcoming results to the homeowners, for the wooden planks should be just the right size and fit precisely together. Any contraction or expansion will ruin the entire hardwood floor furnishing in your house, for they are all connected to one another. Therefore, one should always make sure to keep the humidity level between 40-55%, and not to exceed this amount. Neither should the hardwood floors be installed below ground level, or over concrete without any sheeting underneath. The only way to install solid hardwood floors is to nail them down, and they can later be refinished or recoated several times. Solid hardwood floors are an excellent choice in furnishing your home, regardless of their sensitivity to moisture, for they last for a very long time if they are well taken care of. They last much longer than engineered hardwood floors, for they can be refinished over and over again, which enables them a longer life. They are also much more durable because they are thicker in width and therefore are a much stronger and supportive flooring system.