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Tar paper,roofing paper,felt paper,underlayment, orroofing tar paper is a heavy-dutypaper used inconstruction. Tar paper is made by impregnating paper withtar, producing awaterproof material useful forroof construction. Tar paper is similar toroofing felt,[1] historically afelt-like fabric made from recycled rags impregnated with meltedasphalt, and today evolving into a more complex underlayment of synthetic mesh or fiberglass strands waterproofed by synthetically enhanced asphalt.
Tar paper has been in use for centuries. It is defined as a Grade D building paper—a designation derived from a federal specification in the United States.[citation needed] Sometimes anachronistically referred to as "building paper", tar paper is manufactured from virginkraft paper (as opposed to the fabric-based or synthetic mesh substrates ofroofing felt) impregnated with asphalt. The result is a lighter-weight but less durable product with similar properties to felt.
Grade papers are rated in minutes: the amount of time it takes for a moisture-sensitive chemical indicator to change color when a small boat-like sample is floated on water. Common grades include 10-, 20-, 30-, and 60-minute. The higher the rating, the heavier and more moisture-resistant the paper. A typical 20-minute paper will weigh about 3.3 pounds (1.5 kg) persquare, a 30-minute paper 3.75 pounds (1.70 kg) per square, and a 60-minute paper about 6 pounds (2.7 kg) per square. The smaller volume of material, however, does tend to make these papers less resistant to moisture than heavier felts.
Tar paper is used as a roofing underlayment withasphalt,wood,shake, and otherroof shingles as a form of intermediatebituminous waterproofing. It is sold in rolls of various widths, lengths, and thicknesses – 3-foot-wide (0.91 m) rolls, 50 or 100 feet (15 or 30 m) long and "15 lb" (7 kg) and "30 lb" (14 kg) weights are common in the U.S. – often marked with chalk lines at certain intervals to aid in laying it out straight on roofs with the proper overlap (more overlap for flatter roofs).
It is typically stapled in place, or held withroofing nails, and is sometimes applied in several layers with hot asphalt, coldasphalt (adhesive), or non-asphaltic adhesives.[2]
Older construction typically used a lighter-weight tar paper, stapled up with some overlap, as a water- and wind-proofing material on walls, largely displaced in recent decades by breathable plastichousewrap, commonly in 8-or-10-foot (2.4 or 3.0 m) widths.
In the 19th and early 20th centuries,shacks of wooden frames covered with tar paper were a common form of temporary structure or very low-cost permanent housing in the rural United States and Canada,[3][4] particularly in the temperateAmerican South.