Tar paper is installed before shingles on a new roof.
Tar paper is a waterproof construction material that serves as a base in civil construction. It works as a vapor barrier, keeping moisture out, as well as providing a thin layer of protection against airflow. Tar paper, also called felt, is made from cellulose fibers, glass fibers, or polyester fleece compressed into thin sheets. The tiles are treated with tar or asphalt to make them waterproof. Tar paper is typically installed under shingles, siding, and hardwood floors.
Roofing tar paper is a waterproof building material.
Sold in rolls of various widths, weights, and lengths, tar paper is inexpensive and readily available at home improvement and building supply stores. The most common size rolls are 0.9144 meters wide by 50 or 100 feet (about 15.25 or 30.5 meters) long. It comes in 15 lb or 30 lb (6.8 or 13.6 kg) weights.
The weight designation means the weight of 100 square feet of tar paper. 15 lb. (6.8 kg) tarpaper is less durable than 30 lb. (13.6 kg) tarpaper and is used in less critical areas such as walls and floors. Tar paper is sometimes coated with sand to prevent sticking while being rolled.
The process of installing tar paper is called tar paper siding. It is typically installed on roofs above the sub-roof before installing shingles or gravel. In case of heavy rains, it is possible for the water to go under the tiles. The tar paper works as a secondary line of defense, preventing water from reaching the internal wooden structure.
Tar paper is also applied as a coating on external walls. It is installed under the siding. This not only prevents water from reaching the internal wood structure, but also helps prevent loss of internal heated or cooled air. Tar paper is sometimes used as a vapor barrier and cushioning under hardwood floors, keeping the subfloor dry and helping to prevent hardwood floors from creaking.
Tar paper can help protect a building if exterior items are lost or damaged. For example, if a tile is ripped off during a storm, the underlying tar paper can protect the sub-roof until the tile is replaced. While tar paper is an inexpensive way to provide an extra layer of protection, it is not weather resistant. It will deteriorate if left exposed for long periods of time. Exposed tar paper should be covered as soon as possible to help maintain its integrity.