Short answer
For roofing, tar paper and roofing felt mean the same product: asphalt saturated felt underlayment, sold as #15 (ASTM D226 Type I) or #30 (Type II). The tar in the name is a leftover from older products. What matters when you buy is the grade, whether the label says it is a roofing underlayment, and what your roofing maker and local code accept.
The short history behind the names
The first of these roofs used paper treated with wood or pine tar, later coal tar; as petroleum refining grew, asphalt took over, and by the late 1800s most felts were rag felts saturated with asphalt (National Park Service). The grade names stuck around even as the products changed: IIBEC traces how the 15 lb and 30 lb names became ASTM D226 Type I and Type II (IIBEC), and DECRA notes today’s weights no longer match the numbers (DECRA). The tar in tar paper is the same kind of leftover.
Names you will see in the aisle
| What you might see | What it is | For a roof? |
|---|---|---|
| Tar paper | Usually asphalt saturated felt | Yes, if the label rates it as roofing underlayment |
| Roofing felt, felt paper | Asphalt saturated felt, #15 or #30 | Yes |
| #15 / 15 lb / Type I | The lighter grade | Yes |
| #30 / 30 lb / Type II | The heavier grade | Yes |
| Building paper, house wrap | Wall water resistive barriers | No, unless rated for roofs |
| Synthetic underlayment | Polymer sheet | Yes, where the roofing maker accepts it |
Which to buy
-
01Most jobs
#15 roofing felt
Best for: under roll roofing and shingles that go on right away
- Grade
- Type I
- Width
- 36 in
-
02Tougher
More detail on grades, weights and roll sizes is in the roofing felt guide, and the modern alternative is compared in synthetic vs felt underlayment.
Questions people ask
Is tar paper the same as roofing felt?
In everyday use, yes. Roofers, stores and homeowners use both names for asphalt saturated felt underlayment. Read the label: it will name the grade and the standard it meets.
Why is it called tar paper?
The name is older than today’s products. Early roofing papers were saturated with tar, and the nickname stuck after asphalt became the standard saturant. Ask for roofing felt by grade and you will get what you need.
Can I use building paper on a roof?
Not unless the label says it is rated as roofing underlayment. Wall building papers are made for a different job. Under roofing, use felt or a synthetic or self-adhered underlayment that the roofing maker accepts.
Is 30 lb tar paper twice as good as 15 lb?
It is thicker and tougher, but not exactly twice the weight. DECRA notes #15 now weighs about 7.5 to 12.5 lb per square and #30 about 16 to 27 lb. Compare actual weights if it matters.
Sources
Last reviewed October 12, 2026. Products and listings change; check the data sheet and wrapper before you buy, follow the maker’s instructions, and check your local building code.