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Quick, low-risk steps

  1. Check your roof's slope and material type from ground level or records.
  2. Ask the contractor which underlayment they plan to use and why.
  3. Confirm the underlayment is compatible with your chosen outer roofing material.
  4. Verify that the proposed underlayment meets current Atlanta building code requirements.
  5. Request documentation showing the underlayment's ASTM or manufacturer specifications.

Common Underlayment Types

Asphalt-saturated felt, often called tar paper, has been used for decades. It comes in different weights, typically 15-pound or 30-pound, and provides a basic level of water resistance. It is affordable but can wrinkle or tear if exposed to weather for too long before the outer roofing is installed.

Synthetic underlayments are made from polypropylene or polyethylene. They are lighter, stronger, and more tear-resistant than felt. Many are designed to withstand longer exposure times. They often have a slip-resistant surface, which can improve safety for workers during installation.

  • Asphalt-saturated felt: traditional, economical, but less durable when exposed.
  • Synthetic sheets: high strength, UV-resistant, often with slip-resistant texture.
  • Self-adhered membranes: peel-and-stick, used in vulnerable areas like eaves and valleys.
  • Rubberized asphalt: provides a waterproof seal around fasteners, ideal for low slopes.
  • High-temperature underlayments: required under metal roofs in some climates.

Compatibility with Roofing Materials

Asphalt shingle manufacturers typically specify which underlayments are approved for their warranty. Using an incompatible underlayment can void the warranty. For example, some synthetic underlayments may not be recommended under certain shingles due to heat retention or chemical reactions.

Metal roofs often require a high-temperature underlayment or a specific type of synthetic that can withstand the heat conducted by the metal. Standing seam metal roofs may also need a vapor barrier or ventilation layer, depending on the climate and attic design.

  • Check the shingle manufacturer's installation instructions for approved underlayments.
  • Metal roofs may need high-temperature or specialized underlayments.
  • Tile roofs often require a double layer of underlayment or a high-strength synthetic.
  • Low-slope roofs may require self-adhered membrane across the entire surface.
  • Always ask for documentation of compatibility from the contractor.

Scope Questions to Ask Your Contractor

When comparing quotes, make sure each bid clearly states the type, brand, and thickness of underlayment. Some contractors may include a basic felt in their base price and charge extra for synthetic or self-adhered upgrades. Understanding these details helps you compare apples to apples.

Ask about the attachment method. Underlayment is typically fastened with cap nails or staples, but some synthetics require specific fasteners to maintain the warranty. Also, inquire about the overlap at seams and how valleys, eaves, and penetrations will be detailed.

  • What specific underlayment product will be used?
  • Is the underlayment compatible with my shingles or metal panels?
  • How will the underlayment be attached (cap nails, staples, adhesive)?
  • What is the overlap at horizontal and vertical seams?
  • Will self-adhered membrane be used at eaves, valleys, and penetrations?

Code and Permit Considerations in Atlanta

The City of Atlanta adopts the International Residential Code with local amendments. The IRC requires underlayment for all roof coverings, with specific requirements based on slope and material. For example, asphalt shingles on slopes of 4:12 or greater require at least one layer of underlayment, while lower slopes need two layers or a self-adhered membrane.

Your contractor should pull a permit for a full roof replacement. The permit process includes inspections that verify proper underlayment installation. If you are unsure about current code requirements, contact the City of Atlanta's planning department or ask your contractor to provide the relevant code section.

  • Atlanta building code is based on the IRC with local amendments.
  • Underlayment requirements vary by roof slope and material.
  • A permit is typically required for roof replacement in Atlanta.
  • Inspections will check underlayment installation before shingles go on.
  • Ask your contractor to cite the code section for the proposed underlayment.

Take this with you

Evidence and scope checklist

  • Underlayment type, brand, and thickness specified in quote
  • Compatibility with chosen outer roofing material confirmed
  • Attachment method and fastener type stated
  • Seam overlap and valley/eave detailing described
  • Self-adhered membrane locations identified
  • Code compliance for Atlanta jurisdiction verified
  • Manufacturer warranty requirements for underlayment met
  • Permit and inspection process included in scope
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Common questions

What homeowners ask next

Can I reuse existing underlayment when replacing shingles?

It is rarely recommended. Old underlayment may be deteriorated, torn, or incompatible with new shingles. Most manufacturers require new underlayment for warranty coverage. A full tear-off allows inspection of the deck and proper installation of new underlayment.

Is synthetic underlayment worth the extra cost?

Synthetic underlayment offers better tear resistance, lighter weight, and often longer UV exposure ratings. It can be a good investment, especially if the roof will be exposed for several days before shingles are installed. Compare the specific products and warranties offered by your contractor.

Do I need ice and water shield in Atlanta?

While Atlanta's climate is milder, ice dams are less common, but self-adhered membranes are still required by code in certain areas like valleys and around penetrations. They provide extra protection against wind-driven rain. Ask your contractor if local code requires it and where it will be installed.

Evidence

Sources used for this guide

Research checked July 31, 2026

Optional next step

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