How to Felt a Shed Roof for Long Lasting Waterproofing
The shed roof is a simple but important structure component that protects stored items and the building itself. Felting a shed roof helps seal against moisture, extend the roof’s life, and reduce maintenance. This guide covers selecting the right felt, preparing the deck, and a step-by-step method to achieve a durable, weather-tight layer.
Preparation And Assessment
Assess the existing roof deck before felting. Check for rotten or warped boards, loose nails, and damage to any underlying insulation or underlayment. Replace damaged boards and secure the deck to avoid punctures in the new felt layer. Clear debris, dry the surface, and repair any leaks with roofing sealant. A clean, dry, and solid base is essential for long-term performance.
Choose the correct roof felt for a shed roof. In the United States, asphalt-saturated felt is common, typically sold as 15-pound or 30-pound roll felt. For small structures or higher humidity zones, 30-pound felt offers extra durability. For added protection, consider combining felt with a compatible asphalt or synthetic underlayment. The objective is to create a fatigue-resistant, water-shedding layer that can tolerate temperature fluctuations.
Materials And Tools
Gather the following supplies for a standard shed roof felting project:
- Asphalt-saturated felt rolls (15-pound or 30-pound, depending on climate and budget)
- Roofing nails with wide heads or cap nails suitable for felt installation
- Roofing cement or asphalt roof adhesive for laps
- Utility knife and straightedge
- Measuring tape, chalk line, and a level
- Hammer or nail gun with roofing nails
- Drip edge at eaves and suitable flashing where needed
- Primer or sealer for edges or repairs, if recommended by manufacturer
- Personal protective equipment: gloves, safety glasses, and sturdy footwear
Safety Considerations
Work in daylight and on a dry surface. Use a stable ladder and secure footing on the roof if you must work from above ground level. Avoid steep pitches; if the shed roof is difficult to access safely, consider professional help. When handling sharp tools and hot roofing cement, wear protective gear. Never pace or lean heavily on wet or fragile edges.
Step-By-Step Installation
Follow these steps to ensure a well-sealed, long-lasting felt layer:
- Dry Fit And Mark: Measure the roof width and length. Mark the destination of each felt strip so you know where to start and how to align seams. Plan the laps so that water runs away from the seams.
- Start At The Bottom: Begin with a full-width strip at the lowest edge (eaves). Allow a slight overhang over the drip edge for shedding water. Press the felt into place to prevent air pockets.
- Nail Placement: Fasten the felt with nails every 4–6 inches along the edges and 8–12 inches along the field. Use wash head roofing nails to minimize pull-through. Avoid overtightening nails to prevent tearing.
- Make Laps And Seal: Overlap the next strip by 2–4 inches along the length. Apply a line of roofing cement under the lap to seal. Press the lap firmly to ensure full contact, especially near the edges and nail lines.
- Edge Treatments: Attach drip edge along the lower edge to direct water away from the deck. If there are penetrations or flashing needs, seal them with compatible flashing or roofing cement to prevent leaks.
- Field Seams: For larger sheds, consider reinforcing field seams with a second layer of felt or a seam tape, if recommended by the felt manufacturer. This extra protection helps prevent leaks at seams during heavy rain.
- Ridge And Perimeter Checks: Inspect the ridge area for potential wind uplift. If needed, apply additional nails at the top and seal any nails with sealant to prevent moisture entry.
- Final Inspections: Run your hand over the surface to find loose spots or lifted edges. Re-nail and reseal any areas that show movement. Ensure there is no standing water on the felt after a test rain or shower.
Common Issues And How To Address Them
Weather and aging can cause common problems. Be proactive to extend the life of the felting:
- Peeled Edges: Lifted edges are a sign of poor adhesion or insufficient nails. Re-nail and re-seal the affected laps.
- Punctures Or Tears: Small tears can be patched with asphalt-capable tape or cement. For larger tears, consider replacing the damaged strip to prevent leaks.
- Pooling Water: A flat deck can allow water to pool due to poor drainage. Check for deck dips and add a slight slope away from the house if feasible to improve drainage.
- Wind Uplift: Secure the bottom edge and add extra fasteners along the top edges if high winds are common in your area.
Maintenance And Longevity
Regular inspection extends the life of the shed roof felt. After installation, check annually for loose laps, lifted nails, and any signs of moisture intrusion. Clean debris after heavy storms to prevent moisture pooling and animal nesting. If your climate includes extreme heat or cold cycles, verify the felt and sealant compatibility with your region’s temperatures. Consider resealing or re-felting every 7–15 years, depending on wear, foot traffic, and exposure.
Cost Considerations And Timeframe
Costs vary by region, material quality, and shed size. A typical 8×6 shed roof may require 2–3 rolls of 30-pound felt plus nails and cement, totaling a modest investment. Labor time ranges from half a day to a full day for a novice, with a professional taking less time. Budget for extra materials if you need to repair the deck or address flashing around penetrations.
Tips For Best Results
- Weather Window: Plan felting during dry, mild days to avoid moisture under the felt.
- Manufacturer Guidelines: Always follow the specific instructions on the felt package for nail spacing and sealing techniques.
- Quality Over Speed: Take time to align seams and press laps firmly for a durable seal, especially at edges and corners.