When most homeowners think about their roof, they focus on the visible shingles. But what goes under shingles on a roof is equally important for long-term protection. As Tennessee’s trusted roofing experts serving Crossville, Cookeville, Knoxville, and surrounding areas, Jeff Woods Construction breaks down the critical layers that keep your home dry and secure.
The Complete Roof System
Your roof is a complex system with multiple protective layers working together:
1. Roof Decking (Sheathing)
What it is: The structural foundation, typically ½” to ¾” plywood or OSB (oriented strand board)
Purpose:
- Provides structural support for the entire roof system
- Creates a stable surface for underlayment and shingles
- Distributes weight load across rafters/trusses
Tennessee Considerations: High humidity requires proper ventilation to prevent deck deterioration
2. Underlayment – The Critical Barrier
What it is: A water-resistant barrier installed directly on the roof deck
Types of Underlayment:
Asphalt-Saturated Felt (Traditional)
- #15 or #30 weight options
- Most economical choice
- Good for basic protection
Synthetic Underlayment (Recommended)
- Superior durability and tear resistance
- Better walkability during installation
- Enhanced weather protection
- Longer warranties
Rubberized Asphalt (Premium)
- Self-adhering membrane
- Excellent for high-wind areas
- Superior ice dam protection
- Premium cost but maximum protection
3. Ice and Water Shield
What it is: Self-adhering waterproof membrane
Installation Areas:
- Eaves (first 3-6 feet)
- Valleys
- Around penetrations (chimneys, vents, skylights)
- Rake edges in high-wind zones
Why it’s crucial in Tennessee: Protects against ice dams and wind-driven rain common in our region
4. Drip Edge
What it is: Metal flashing along roof edges
Purpose:
- Directs water away from fascia boards
- Prevents water infiltration under shingles
- Protects roof deck edges
Installation Process – The Jeff Woods Way
Step 1: Deck Inspection and Preparation
- Inspect existing decking for damage
- Replace any compromised sections
- Ensure proper fastening and ventilation
Step 2: Drip Edge Installation
- Install along eaves before underlayment
- Install along rakes after underlayment
Step 3: Ice and Water Shield Application
- Apply to vulnerable areas first
- Ensure proper overlap and adhesion
- Pay special attention to valleys and penetrations
Step 4: Underlayment Installation
- Roll out parallel to eaves
- Maintain proper overlap (typically 6″ side, 4″ end)
- Secure with appropriate fasteners
- Create proper tie-ins around penetrations
Step 5: Shingle Installation
- Begin with starter course
- Follow manufacturer specifications
- Maintain proper exposure and overlap
Climate Considerations for Middle Tennessee
High Humidity: Synthetic underlayments resist moisture better than felt
Temperature Extremes: Quality underlayments handle thermal shock better
Storm Activity: Ice and water shield protects against wind-driven rain
Elevation Variations: From Crossville’s plateau to Knoxville’s valleys, elevation affects material choices
Common Mistakes to Avoid
- Skipping Ice and Water Shield – False economy that leads to expensive repairs
- Improper Overlap – Leaves gaps for water infiltration
- Wrong Fasteners – Inadequate attachment leads to blow-offs
- Ignoring Ventilation – Poor airflow causes premature deterioration
When to Replace Underlayment
Signs you need new underlayment:
- Frequent roof repairs
- Interior water damage despite good shingles
- Visible deterioration during inspections
- Age (20+ years for felt, 25+ for synthetic)
Why Professional Installation Matters
Proper underlayment installation requires:
- Knowledge of local building codes
- Understanding of Tennessee weather patterns
- Experience with various roofing materials
- Access to professional-grade materials
Jeff Woods Construction Advantage
With over 25 years serving the Upper Cumberland region, we understand what goes under shingles on a roof in Tennessee:
- GAF and CertainTeed Certified – Access to premium materials and extended warranties
- Local Expertise – Understanding of regional weather challenges
- Quality Installation – Three generations of craftsmanship
- Comprehensive Service – From custom homes to roof repairs
Get Your Roof System Right
Don’t compromise on what goes under your shingles. The hidden layers of your roof system are just as important as the visible ones. Contact Jeff Woods Construction for a comprehensive roofing solution that protects your Tennessee home for decades to come.
Ready for a professional assessment? Call (931) 787-7715 or visit our Crossville location for a free consultation.
