What Is Roof Underlayment and Why Is It Critical for Arizona Homes?
Roof underlayment is a water-resistant or waterproof layer installed directly over your roof’s plywood deck, but beneath the final roof covering—whether that’s tile, shingle, metal, or foam. It serves as the last line of defense against water infiltration, wind-driven rain, dust, and even ice dams.
In Arizona, underlayment plays a critical role because tiles and shingles themselves are not entirely waterproof—they are primarily water-shedding. Underlayment bridges the gaps, seals the roof deck, and prevents leaks in case of cracked tiles, missing shingles, or heavy monsoon downpours. It’s a building code requirement for all new roofs and replacements, and the quality of this hidden layer can determine your home’s comfort, safety, and longevity.
- Felt (Asphalt-Saturated): Traditional and cost-effective, but less durable than modern synthetics. Common for shingle roofs; rated by weight (15 or 30 lb).
- Synthetic (Polypropylene/Polyethylene): Lightweight, tear-resistant, and superior in Arizona’s heat. Resists UV, moisture, and often used beneath tile or metal roofs for its longevity.
- Self-Adhered (Peel-and-Stick): Premium, waterproof, and ideal for roof valleys, eaves, or entire decks in storm-prone areas. Great for added protection under tile or in low-slope sections.
High-quality underlayment improves wind resistance, prevents mold/rot, and can extend roof life by a decade or more. It also acts as a barrier during the construction phase—protecting your home before tiles or shingles are installed.
Arizona’s heat, dust, and sudden monsoon rains put every roof to the test. Underlayment is your insurance against small failures in tile, shingle, or foam coatings. Without it, water can seep into the deck, causing rot, mold, and interior damage—leading to costly repairs or even structural issues.
Most roof leaks in Arizona originate from aged, deteriorated, or improperly installed underlayment—rather than from the tile or shingle itself. That’s why reputable contractors always inspect and often recommend replacing underlayment every 15–30 years, even if your roof covering looks intact.
Mesa’s building codes require quality underlayment for all new roof installations and major repairs. Local roofers recommend synthetic underlayment for its superior performance and lifespan in Arizona’s climate. When re-roofing, always budget for new underlayment and request documentation for warranty and insurance purposes.
Regular inspections—especially after monsoon season—can catch signs of underlayment failure early. Look for ceiling stains, missing tiles, or visible wear around vents and valleys. Investing in high-grade underlayment now means a safer, drier, and longer-lasting home.
Have questions about your roof’s underlayment or maintenance needs? Share your experience below, and check back for more expert guidance on Arizona roofing solutions.
