How to apply tar paper

Updated February 21, 2017

Tar paper, sometimes called roofing felt or tarred board, is made of durable heavy-duty paper covered with tar. Tar paper is placed on top of roofs before shingles, asphalt or shakes are installed. Tar paper prevents moisture from soaking into a building's roof and ceiling.

Once you are comfortable applying tar paper, you can apply tar paper to most average-sized homes in about one hour. Tar paper can be purchased from larger home and garden or hardware stores.

Measure your roof to determine how much tar paper you need. Measure the length and width of the roof using the measuring tape. Multiply these two numbers together to determine the roof's square footage. Round this number up and add 5% to this final number to determine how much tar paper you need.

For example, if you measure the width of your roof as 36 feet and the length of your roof as being 40, the square footage of your roof is 1,440. Round this number to 1,500. Add per cent to equal 1,575. You will need 1,575 square feet of tar paper to cover your roof.

Determine how many nails you will need. To ensure you have enough nails, purchase one nail for every 12 inches of your roof's square footage. To determine this number, divide the square footage of your roof by 12. Thus, if your roof is 33,600 square feet, you need approximately 2,800 nails

Write down our calculations.

Place the first roll of tar paper at one corner of the roof, by an edge. Roll the tar paper roll out along the length of the roof. Smooth out the tar paper so there are no wrinkles, gaps or bubbles. Hammer one nail into corner edge of the tar paper with the hammer tacker. Continue to hammer nails along the edge of the roof at 12-inch intervals.

Roll the next piece of tar paper out along the length of the roof, overlapping the other piece of tar paper by 4 to 6 inches. Smooth the piece of tar paper so there are no gaps, bubbles or wrinkles. Hammer the tar paper into place, every 12 inches, as you did before.

Repeat Steps 3 and 4 until the entire roof is covered with tar paper.

If you have more tar paper than the length of the roof, cut off the excess tar paper. If you need to start a roll of tar paper in a section of roof that is not the edge, overlap this piece of tar paper with the already installed tar paper by 6 inches.


Be careful when on the roof or climbing a ladder to avoid falls. Do not work on a roof in inclement weather.

Things You'll Need

  • Measuring tape
  • Pencil
  • Paper
  • Tar paper
  • Hammer tacker
  • Short galvanised nails or roofing nails
  • Cutting blade
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About the Author

Marguerite Lance has been a professional writer for seven years and has written for museums, hospitals, non-profit agencies, governmental agencies and telecommunication companies. Her specialties include nutrition, dietetics and women's and children's health issues. Lance received a Bachelor of Arts in biological anthropology from Idaho State University.