Solid wood
Wood doors, equal parts hard working and good looking, are made either with a solid piece of wood or with an engineered-wood core interior and a wood veneer exterior. A true solid wood door is often used at the front entry, as it can be made to include eye-catching architectural details, such as intricate carvings. Solid wood doors are durable when protected against the elements and insulate well against heat, cold and sound.
Hollow Core
The least expensive option in the door market, hollow-core doors are also the most common. Because they are filled with a cardboard-type center, they are extremely light weight and are easy to install. Most commonly used in bedrooms, bathrooms and closets, they are less likely to warp with moisture and temperature changes than their solid-core cousins, but they are prone to wear and tear and provide minimal sound blockage.
Solid core
Made with a core of composite wood (such as MDF), solid core doors are finished on the exterior with layers of veneer, which can be stained or painted. Because of their construction, solid core doors are heavy and must be installed properly to avoid sagging. They’re less commonly used than their hollow-core counterparts due to their cost (about 50 percent more) but are popular for rooms where sound dampening is desired, such as a home office.
Metal
Metal doors are made of thin sheets of steel surrounding a core of polyurethane foam. They stand up well against rigorous everyday use and the elements, making them common in exterior applications. Besides providing strength and durability, metal doors are fire and noise resistant (ideal for garage access inside the home). Take note that they must be maintained regularly to guard against rust and have minimal insulating properties.
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