How to Decide on the Best Underlayment for Your Roof
Installing a high-quality roof underlayment is one of the most important steps when replacing your roof or building a new structure. But with so many underlayment options on the market, how do you determine which one is the best for your specific roof and climate needs?
We'll overview the main underlayment types, provide recommendations based on your roof materials and environmental conditions, and discuss performance considerations as well as budget and installation.
Understand the Main Underlayment Types
The first step is gaining familiarity with the basic categories of roofing underlayment materials and their characteristics:
Asphalt/Tar Paper
Asphalt or tar paper is a commonly used, economical roofing underlayment made from an asphalt-saturated felt or fiberglass mat. It provides a water-resistant layer beneath shingles or other roof coverings.
Pros: inexpensive, compatible with many roof types
Cons: absorbs moisture, less durable than synthetic options
Best for: budget-friendly underlayment for shingle roofs
Synthetic Underlayments
Synthetic underlayments are made from woven or non-woven polypropylene or polyethylene polymers. They are lighter, thinner and more tear-resistant than asphalt paper.
Pros: durable, breathable, resistant to mold growth
Cons: more expensive upfront cost
Best for: long-lasting protection under shingles, metal panels
Rubberized Asphalt
Rubberized asphalt underlayments feature a top layer of rubber or thermoplastic polymers bonded to an asphalt layer, enhancing flexibility and water resistance.
Pros: extremely waterproof protection, allows expansion and contraction of roof
Cons: more difficult installation, expensive
Best for: high movement roofs like metal or tile; cold climates
Peel-and-Stick Membranes
Self-adhering underlayments offer adhesive strips, letting them securely bond to the roof deck without nails or other fasteners.
Pros: superior waterproofing, no penetration risk, DIY-friendly
Cons: can be prone to buckling without fasteners, expensive
Best for: low-slope or awkwardly shaped roofs; additional protection in valleys or eaves
Consider Your Roof Type
The underlayment you choose should always align with the specific covering or roofing materials being used.
Asphalt Shingles
For asphalt shingle roofs, #30 felt paper or a synthetic equivalent provides adequate leakage protection at a reasonable cost in most regions.
In northern climates or on steep-pitched roofs, a rubberized ice and water barrier is recommended for high risk areas like eaves, valleys and roof penetrations. This boosts protection against ice dams and wind-driven moisture.
Metal Roofing
Due to expansion and contraction of metal roofing panels, a rubberized underlayment is ideal as it maintains flexibility across a wide temperature range.
Options like Titanium UDL30 synthetics offer durable water resistance with a slip-resistant film for stable metal panel installation.
Tile Roofing
Concrete or clay tile roofs benefit from a synthetic underlayment, providing a breathable and mold-resistant support layer on the sheathing.
For heavy or irregularly shaped tiles, a high traction option like RoofTop Guard II helps prevent slippage during installation.
Low-Slope Roofs
On flat or low-pitched roofs, a self-adhering underlayment is often the best choice as it seals around fasteners and offers leak-free protection.
MFM Wind & Water Seal with a strong adhesive backing bonds firmly to the roof deck while allowing heat welding of the membrane above.
Factor in Climate and Weather
Regional climate is a major determinant of which underlayment type will perform best.
Hot and Humid Climates
In hot and rainy southern regions, focus on breathability and moisture resistance. Synthetic, water-resistant products allow interior humidity to escape while keeping exterior water out.
Top choices: GAF Deck-Armor, DuPont Tyvek Protec
Cold and Snowy Climates
Where heavy snow and ice dams are common, insulation and impenetrable waterproof membranes are vital. Rubberized asphalt mixes reinforced with polymer fabrics provide superb protection.
Top choice: Polyglass Polystick MTS Plus
Coastal Areas
Salt spray and high winds demand durable, rugged underlayments. Look for impact resistant synthetics featuring integrated sealants around fastener holes.
Top pick: Atlas StormMaster Shake Underlayment
Consider Performance Needs
Determining the level of performance needed relative to water protection, wind uplift resistance and longevity can further narrow suitable underlayment products.
Water and Leak Protection
In wet regions or flat roofs, waterproofing is key. Seek underlayments with integrated adhesives rather than relying solely on fasteners, which can back out or loosen over time.
Top picks: Grace Ice & Water Shield HT, Henry Blueskin PE200 HT
Wind Resistance
In hurricane zones or high elevation areas, underlayment tear strength and uplift resistance are essential. Synthetics like polyester mats provide durability under extreme loads.
Top pick: Dow Weathermate Plus
Longevity and Durability
For a lasting underlayment that won't need frequent replacement, thick reinforced rubbers and polymer modified asphalt blends perform consistently across decades.
Top picks: CertainTeed RoofRunner, InterWrap RhinoRoof U20
Installation and Budget Factors
Ease of Installation
For do-it-yourselfers, an underlayment that goes down quickly and easily is key. Look for mechanically fastened synthetics rather than adhesives.
The easiest to install are lightweight polypropylene felts such as RoofTop Guard II.
Budget Considerations
Less expensive roofing felts run $50 to $250 for a 3-square roll (100 sq.ft.) whereas premium rubberized underlayment can cost $1000 or more per roll.
Focus spending on high-risk areas and buy cheaper products for general coverage. Also consider long-term costs from premature replacement of cheaper underlayments.
The optimal underlayment comes down to roof materials, climate, budget and desired features like traction, breathability and leak protection.
As an all-around performer, a reinforced synthetic underlayment like GAF Tiger Paw offers durability at a reasonable mid-range price point for most asphalt shingle roofs.
Ultimately the right product matches your risk profile - prioritizing water resistance for flat or low sloped roofs and tear strength for steep-pitched or metal panel applications.
By weighing all these decision criteria, you can determine the ideal underlayment to keep your roof safely protected across its service life.