What Goes Under Shingles on a Roof? A Complete Guide
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:
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.
