What Is A Tar Paper In Construction?
What Is A Tar Paper?
Tar paper is a heavy-duty paper that is used in construction. It is made by impregnating paper or fiberglass mat with tar, creating a waterproof material that is useful for roof construction.
Tar paper is different from roofing felt, which is impregnated with asphalt instead of tar, but both products are used in the same way and their names are sometimes used interchangeably.
Tar paper has been used for centuries and was originally made from recycled rags, but modern tar paper is made from recycled paper products such as cardboard and sawdust. The most common product is #15 felt, which before the oil crisis, weighed about 15 pounds per square, hence the asphalt-impregnated felt was called “15-pound felt”.
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 7.5 to 12.5 pounds per square, depending on the manufacturer and the standard to which felt is made.
A thicker and stronger variant, once known as 30-pound felt (30#), is number 30 felt (#30), which usually weighs 16 to 27 pounds per square.
Tar paper is more accurately a Grade D building paper, which 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 3.3 pounds per square, a 30-minute paper 3.75 pounds per square, and a 60-minute paper about 6 pounds per square.
However, the smaller volume of material in these papers tends to make them less resistant to moisture than heavier felts.
Uses Of Tar Paper
Tar paper is a waterproof and weather-resistant material that is used as an underlayment for various types of roofing, such as asphalt, wood, shake, and gravel. It comes in rolls of different widths, lengths, and thicknesses and is commonly marked with chalk lines to aid in proper installation with the correct overlap.
The rolls can be installed with staples or roofing nails, or applied in layers with hot or cold asphalt or non-asphaltic adhesives. Historically, tar paper was also used as a low-cost housing material in the form of wooden frames covered with tar paper in rural parts of the United States and Canada.
However, in modern construction, housewrap is more commonly used as a water and wind-proofing material on walls.
Can Tar Paper Get Wet?
Tar paper, also known as roofing felt, is an essential layer in a roofing system. It sits between the plywood and shingles, providing a buffer and support for the shingles. Although it is designed to repel water, it can only handle a certain amount of exposure to water.
If it is exposed to too much water it can become damaged and lose its ability to protect the roof’s integrity.
This can lead to holes and leaks in the roof layers causing more problems than it solves. It is important to ensure that tar paper is not left wet for prolonged periods of time to prevent the breakdown of fibers and fraying.