Roofing underlayment is a layer of material that goes under shingles, tiles, or metal roofing to add extra protection to a roof deck. It serves several important functions:

• Water Resistance: Underlayment creates a water-resistant barrier to prevent leaks from wind-driven rain and moisture that gets past the external roof covering. This keeps water from penetrating and damaging the roof deck.
• Leak Protection: If water gets through the shingles or tiles, the underlayment contains the leak and prevents widespread water damage while the external roofing is being repaired. 
• Temperature Regulation: Some underlayments provide insulation that keeps attics cooler in summer and warmer in winter, reducing energy costs.
• Impact Absorption: Felt underlayments cushion the roof deck from hail and debris impacts, helping to maintain the roof’s integrity.
• Longevity: A good underlayment can extend the lifespan of shingles or tiles by smoothing out the roof deck and preventing deterioration from underneath.

Roofing underlayments serve as an additional barrier against water intrusion, acting as a secondary line of defense behind the roof shingles. They effectively channel water away from the roof deck, preventing leaks and moisture damage to the interior of your home.

Roof sheathing, the wooden layer that supports the roof shingles, is susceptible to rot and decay when exposed to moisture. Roofing underlayments shields the sheathing from water damage, extending its lifespan and maintaining the structural integrity of your roof.

Ice dams, ridges of ice that form at the edge of a roof, can cause significant damage if they melt and back up under the shingles. Self-adhered underlayments, with their waterproof seal, effectively prevent ice dams from forming, protecting your roof from this potential hazard.

By preventing water damage and protecting the underlying roof components, roofing underlayments contribute significantly to the overall durability and longevity of your roof. This can save you money on costly repairs and replacements in the long run.

Roofing underlayments work in conjunction with the roof shingles to form a cohesive weatherproofing system. They help to evenly distribute the weight of the roofing materials, reducing stress on the structure and enhancing the overall performance of your roof.

A properly installed roofing underlayment can help to minimize heat transfer through the roof, contributing to better insulation and energy efficiency. This can lead to lower energy bills and reduced environmental impact.

This is made of fibers bonded with asphalt adhesive. It is durable, breathable, and helps prevent wind-driven rain from penetrating the roof deck and interior spaces. Common types include organic roofing felt and fiberglass roofing felt.

This is a water resistant woven or sheet material made from synthetic plastic based materials like polyethylene or polypropylene. It is more tear resistant than felt and lasts longer. Brands include Tyvek and Typar. 

This has a thick asphalt adhesive pre-applied to one side that bonds it directly to the roof deck without using nails or staples. It creates a water tight seal and is used mainly around vulnerable areas like valleys and eaves. Types include rubberized asphalt and ice and water shield membranes.

Ice and water shield is a critical component of many roofing systems, particularly in areas prone to ice dams and heavy snowfall. It acts as a secondary barrier against water intrusion, protecting your roof deck and underlying structure from damage.

This multi-layer product combines materials like plastic film, woven scrim, polyethylene, adhesive, and sometimes lightweight aluminum. It balances durability with a lighter weight making it easier to install. GAF Deck Armor and CertainTeed RoofRunner are two examples.

• High Rainfall: Opt for water-resistant underlayments like rubberized asphalt or synthetic.
• Snow and Ice: Consider self-adhering options or those with high tear strength to handle heavy snow.
• Extreme Heat: Choose a reflective underlayment to help regulate attic temperature.

• Asphalt Felt: Affordable but less durable, susceptible to tears and rot.
• Synthetic Underlayment: Lightweight, durable, water-resistant, and mold-resistant.
• Metal Roof Underlayment: Specialized options for metal roofs, offering high heat resistance.

• Asphalt Shingles: Compatible with most underlayments.
• Metal Roofs: Requires specialized underlayment for proper adhesion and heat protection.
• Concrete Tiles: Can use most underlayments, except for asphalt-saturated felts.

• Self-Adhering: Easier installation, especially on steep roofs.
• Ice and Water Shield: Provides extra protection against ice dams and leaks.
• Walkability: Opt for underlayments with good walkability for easier installation and maintenance.

• Clear the Roof Deck: Remove any debris, nails, or old underlayment remnants.
• Ensure Proper Ventilation: Check for adequate attic ventilation to prevent moisture buildup.
• Inspect Flashing: Ensure all flashing around vents and chimneys is properly installed and sealed.

• Start at the Eaves: Roll out the underlayment parallel to the eaves, overlapping the edges by at least 3 inches.
• Use Ice and Water Shield: Apply ice and water shield along eaves, valleys, and around vents and chimneys.
• Seal Overlaps: Use roofing cement or compatible sealant to secure all overlaps and penetrations.
• Nail or Staple: Follow manufacturer’s instructions for securing the underlayment with nails or staples spaced appropriately.
• Work Your Way Up: Continue rolling out and securing the underlayment, working uphill and ensuring proper overlap.

• Cut Around Vents and Pipes: Carefully cut openings for exhaust vents and pipes, ensuring proper sealing.
• Inspect for Gaps or Tears: Before installing shingles, check the entire underlayment for any gaps or tears and seal them promptly.
• Follow Manufacturer’s Instructions: Always refer to the specific underlayment manufacturer’s instructions for installation details and safety precautions.

• Wear Protective Gear: Always wear safety glasses, gloves, and sturdy footwear when working on the roof.
• Work with a Partner: Never work alone on the roof, especially if it is steep or slippery.
• Be Cautious of Weather Conditions: Avoid working on the roof in wet, windy, or icy conditions.
• Use Proper Safety Equipment: Utilize ladders and harnesses securely to prevent falls.