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Tar paper is a heavy-duty
paper Paper is a thin sheet material produced by mechanically or chemically processing cellulose fibres derived from wood, rags, grasses or other vegetable sources in water, draining the water through fine mesh leaving the fibre evenly distribu ...
used in
construction Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and ...
. Tar paper is made by impregnating paper or fiberglass mat with
tar Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat. "a dark brown or black bi ...
, producing a
waterproof Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environme ...
material useful for
roof A roof ( : roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of t ...
construction. Tar paper is distinguished from
roofing felt Bituminous waterproofing systems are designed to protect residential and commercial buildings. Bitumen (asphalt or coal-tar pitch) is a mixed substance made up of organic liquids that are highly sticky, viscous, and waterproof. These systems are ...
, which is impregnated with
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
instead of tar, but these two products are used the same way, and their names are sometimes used informally as synonyms.


Description

Tar paper has been in use for centuries. Originally, felt was made of
recycled Recycling is the process of converting waste materials into new materials and objects. The recovery of energy from waste materials is often included in this concept. The recyclability of a material depends on its ability to reacquire the p ...
rags, but modern felt is made of recycled paper products, typically cardboard, and sawdust. The most common product is #15 felt. Before the oil crisis, felt weighed about per
square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length a ...
, hence the asphalt-impregnated felt was called "15-pound felt" (15#). Modern, inorganic mats are no longer the same weight, and to reflect this fact, the new felts are called "number 15 felt" (#15). Modern #15 mats can weigh from pounds per square, depending on the manufacturer and the standard to which felt is made (such as , , or none). A thicker and stronger variant, once known as 30-pound felt (30#), is number 30 felt (#30), which usually weighs per square. Tar paper is more accurately a Grade D building paper—the Grade D designation is derived from a federal specification in the United States—and is widely used in the West. Building paper is manufactured from virgin kraft paper, unlike felts, and then impregnated with asphalt. The longer fibers in the kraft paper allow for a lighter-weight product with similar and often better mechanical properties than 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 per square, a 30-minute paper per square, and a 60-minute paper about per square. The smaller volume of material, however, does tend to make these papers less resistant to moisture than heavier felts.


Uses

Tar paper is used as underlayment with
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
,
wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin ...
, shake, and other
shingles Shingles, also known as zoster or herpes zoster, is a viral disease characterized by a painful skin rash with blisters in a localized area. Typically the rash occurs in a single, wide mark either on the left or right side of the body or fac ...
, or even gravel, since tar paper itself isn't particularly wind- or sun-resistant. It is sold in rolls of various widths, lengths, and thicknesses – rolls, long and "15 lb" () and "30 lb" () 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 can be installed in several ways, such as staples or roofing nails, but it is also sometimes applied in several layers with hot asphalt, cold
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
(adhesive), or non-asphaltic adhesives. Older construction sometimes used a lighter-weight tar paper, stapled up with some overlap, as a water- and wind-proofing material on walls, but modern carpenters more often use widths of
housewrap Housewrap (or house wrap), also known by the genericized trademark homewrap (or home wrap), generally denotes a modern synthetic material used to protect buildings. Housewrap functions as a weather-resistant barrier, preventing rain or other fo ...
.


References

{{reflist Building materials Paper Roofs Moisture protection Roofing materials