Roof felt is a practical, affordable option for protecting shed roofs from the elements. This guide covers how to choose the right shed roof felt, understand the different types, and install and maintain it for reliable, long-lasting performance. By focusing on durability, weather resistance, and ease of installation, homeowners can extend the life of their sheds while keeping stored items dry and secure.
What Roof Felt Is And Why It Matters
Roof felt, often referred to as shingle felt or underlayment, is a waterproof or water-resistant layer placed under the roof covering. For sheds, it provides an additional barrier against moisture penetration, especially during rain, snow, and fluctuating temperatures. The felt reduces the risk of wood rot, mold, and damage to stored tools and materials. It is typically installed over roof decking and beneath the final roofing material, acting as a secondary defense if the outer layer leaks.
Types Of Shed Roof Felt
Understanding the main categories helps match the choice to climate, budget, and DIY skill. The most common shed roof felt options include:
- Bitumen Felt (asphalt-saturated felt): A traditional option offering good water resistance at a low cost. It is durable enough for many garden sheds and is relatively easy to install with basic tools.
- Self-Adhering Felt: Also known as self-adhesive underlayment, this type has a sticky backside that adheres to the roof deck. It provides convenient installation and excellent moisture barrier properties, with fewer wrinkles when applied correctly.
- Cold-Apply Asphalt Felt: Requires membrane and asphalt cement or adhesive to seal joints. It’s widely available, usually budget-friendly, and suitable for standard shed roofs.
- Synthetic Underlayment: Made from polymer-based materials, these felts are lightweight, tear-resistant, and often more durable than traditional bitumen felts. They perform well in extreme weather and are less prone to wrinkling.
Consider climate and roof design when choosing felt. In areas with heavy rainfall or snow, a higher-performance synthetic or dual-layer system may offer better protection.
Key Factors To Consider When Choosing Shed Roof Felt
Several factors influence the right selection for a shed roof:
- Climate: Regions with frequent rain, snow, or temperature swings benefit from higher moisture resistance and UV stability.
- Roof Slope: Sloped roofs shed water more efficiently, but very shallow pitches may require a more robust underlayment to prevent leaks.
- Durability: Synthetic underlayments typically last longer and resist tearing during installation and wind uplift.
- Ease Of Installation: DIY projects favor self-adhesive or cold-applied felts for simpler application and fewer joints.
- Cost: Bitumen and cold-applied felts are budget-friendly, while high-end synthetic felts suit long-term performance at higher upfront cost.
- UV Resistance: Some felts degrade under sun exposure; look for UV-stable products if the roof will be exposed for extended periods before the final roofing layer is installed.
Installation Steps For Shed Roof Felt
Proper installation is essential for optimal performance. The steps below outline a typical process for shed roofs with standard decks:
- Prepare The Roof: Remove debris, inspect decking for damage, and repair any gaps. Ensure the roof surface is dry and clean before applying felt.
- Measure And Cut: Cut the felt sheets to fit the roof area with extra length over the eaves. Allow for 2 to 4 inches overhang beyond the edges to shed water away from the walls.
- Starter Row: Begin at the bottom edge with a starter strip to create a clean, straight line. For self-adhesive felt, peel back a small section and adhere while smoothing from the center outward.
- Apply Felt In Rows: Overlap each subsequent row by 2 to 4 inches, ensuring proper alignment and avoiding wrinkles. Use a roller to press firmly and remove air pockets.
- Sealing Joints: For non-self-adhesive felts, apply cold adhesive or asphalt cement along joints. Ensure seams are fully sealed to prevent water ingress.
- Edge And Ridge Coverage: Extend felt over the eaves and rakes as needed, trimming neatly at edges. If roofing shingles or metal panels will cover the felt, ensure the felt layer remains fully protected beneath.
Safety note: Use a sturdy ladder, wear slip-resistant footwear, and work with a partner when handling long sheets. Do not install in high wind or wet conditions to avoid slips.
Maintenance And Longevity
Appropriate maintenance extends the life of shed roof felt. Key practices include:
- Inspect Regularly: Check for wrinkles, tears, or lifted edges after storms or seasonal changes. Address issues promptly.
- Clean Debris: Remove leaves and debris that can trap moisture and degrade the felt over time.
- Repair Promptly: Patch small tears with compatible patch tape or additional felt strips; replace severely damaged sections when needed.
- Protect From UV: If the final roofing material will not be installed for some time, consider UV-protective coverings or temporary membranes to limit sun exposure.
- Ventilation Considerations: Ensure adequate attic or shed roof ventilation to reduce humidity and prolong felt life, especially in shed designs with attic space.
Common Problems And Troubleshooting
Some frequent shed roof felt issues and how to handle them:
- Wrinkles Or Bubbles: Often caused by improper adhesion or temperature fluctuations. Re-smooth and re-seal affected areas; replace severely wrinkled sections if necessary.
- Peeling Edges: Winds can lift edges. Reattach with adhesive and cover with additional starter strips or edge sealant.
- Leaks At Seams: Joints may fail due to poor sealing. Reapply sealant or replace the faulty section with extra felt.
- Cracking In Cold Weather: Some materials become stiff and crack. Choose temperature-rated materials or wait for milder conditions for installation.
Safety Considerations When Working On A Shed Roof
Roof work carries fall risks. To mitigate hazards:
- Use a sturdy ladder and fall protection if necessary.
- Wear non-slip footwear and gloves for grip and protection.
- Avoid working in high winds, rain, or extreme heat.
- Lift and handle sheets with a partner to reduce strain and prevent drops.
Cost And Value
Cost varies by material, roof size, and contractor vs. DIY installation. Typical shed roof felt costs range from a modest per-square-foot price for basic bitumen felts to higher prices for synthetic underlayments. While initial costs differ, longer-lasting felts and higher-durability options can reduce maintenance and replacement frequency, delivering greater long-term value. Budget for accessories such as adhesives, sealants, and edge trims to ensure a complete, watertight installation.
Frequently Asked Questions
Q: How long does shed roof felt last? A: Most traditional bitumen felts last 5–10 years, while synthetic underlayments can last 15–30 years depending on climate and maintenance.
Q: Can shed felt be installed over existing shingles? A: It depends on the underlying surface; in many cases, a clean, smooth deck is required for proper adhesion and performance.
Q: Should I install felt before the final roof covering? A: Yes, felt acts as an important moisture barrier beneath the final roofing material.
Q: Is DIY shed felt installation worth it? A: For many homeowners, DIY can save money and be straightforward with self-adhesive or cold-applied felts and careful preparation.