Solid hardwood floors are made of planks milled from a single piece of timber. Solid hardwood floors were originally used for structural purposes, being installed perpendicular to the wooden support beams of a building known as joists or bearers. With the increased use of concrete as a sub-floor in some parts of the world, engineered wood flooring has gained some popularity. However, solid wood floors are still common and popular.
Solid wood floors have a thicker wear surface and can be sanded and finished more times than an engineered wood floor. It is not uncommon for homes in New England, Eastern Canada, and Europe which are several hundred years old to have the original solid wood floor still in use today.
The two most popular modern finishes for wood flooring are oil-modified urethane and water-based polyurethane. Within both categories there are many variations and other names used to describe the finish. Oil-modified urethane and water-based polyurethane also have very different refinishing and maintenance regimes.