Asphalt Felt (Underlayment)

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Asphalt Felt (Underlayment)

What is Asphalt Felt (Underlayment)?

Asphalt Felt, A roofing underlayment of asphalt impregnated paper providing secondary water protection beneath shingles.

Description

Asphalt Felt, often called tar paper, is a cellulose or fiberglass mat saturated with asphalt to create a water‑shedding sheet installed over roof decking before shingles or metal panels. #15 felt weighs about 15 lb per 100 sq ft, while #30 provides heavier duty. Felt underlayment smooths decking irregularities, cushions shingles, and offers a temporary dry‑in before final roofing.

FAQs

  • What sizes does asphalt felt come in?

    Rolls 3 ft wide by 144 ft long for #15, 72 ft long for #30.

  • Is it felt required under shingles?

    Most codes and manufacturers require the use of underlayment.

  • How does it feel fastened?

    Staples or cap nails spaced 12 in o.c. with 2 in laps.

  • Can felt be left exposed?

    It provides short-term weather protection, typically lasting up to 30 days.

  • What is synthetic underlayment?

    Polypropylene sheets replacing traditional felt with higher tear strength.

  • Who installs asphalt felt?

    Roofing crews during the dry-in stage.

  • Does felt improve fire rating?

    It contributes to Class A assemblies when combined with shingles.

Fun Fact

Fun Fact: Tar paper roofs were standard on early 1900s prairie homesteads before asphalt shingles became affordable.

CSI Code

07 30 00

NAHB Code

730