How to Re-Felt a Shed Roof for Longevity

The shed roof is a simple structure that often bears the brunt of weather. Refelting a shed roof restores waterproofing, protects the interior, and extends the life of the building. This guide provides a clear, step-by-step approach using common materials and tools, with practical tips to ensure a durable finish and a long-lasting seal against moisture.

What You Need To Know About Refelting A Shed Roof

Refelting a shed roof involves replacing old or damaged roofing felt with fresh underlayment to create a water-tight barrier. The process is straightforward for most shed roofs with a simple slope. Key considerations include choosing the right felt material, ensuring adequate ventilation, and sealing seams properly. Proper preparation and weather conditions are essential for a successful job.

Tools And Materials

• New roofing felt (asphalt or fibreglass/asphalt mix, weight varies by project)
• Roofing nails or cap nails with washers
• Roofing cement or sealant
• Roofing tacks and a hammer or a staple gun (depending on felt type)
• Utility knife or shears
• Measuring tape, chalk line, and a straightedge
• Putty knife and brush for sealant
• Work gloves and safety glasses
• Ladder or scaffolding and a stable work surface
• Primer or bonding agent (optional, for very porous boards)

Preparation Steps

Preparation ensures the new felt adheres well and lasts. Start by inspecting the roof deck for damage—replace rotten or warped boards and secure loose planks. Clean the surface to remove dirt, dust, and algae. If the shed has vents, ensure they are clear and functioning. For nails and screws, countersink or replace any protruding fasteners to create a smooth base. If the existing felt is peeling, remove it completely to expose a clean surface. Finally, check the weather and plan for dry, mild conditions.

Step-By-Step Guide To Refelting

1. Measure the roof and cut the new felt sheets to fit, allowing for overhang at edges.
2. Start at the bottom edge and lay the first strip, ensuring a slight overhang outward to shed water.
3. Seal the top edge of each strip with a beat of roofing cement or sealant and press firmly to prevent air pockets.
4. Nail or tack along the edges using appropriate fasteners with waterproof washers, spacing about 12 inches apart.
5. Overlap subsequent strips by about 3-4 inches to create a continuous water barrier, then secure and seal.
6. Continue up the roof, working in sections and maintaining even tension to prevent wrinkling.
7. Finish with a final sealant along all exposed edges and at penetrations (ridges, joints, and vents).

Sealing Details And Overlaps

Proper overlaps are critical for preventing water penetration. Use at least a 3-4 inch overlap for each strip, ensuring that overlaps run in the same direction to guide water off the roof. When sealing, apply generous amounts of roofing cement at all seams and along the nail lines. Pay special attention to any roof joints or corners where moisture tends to accumulate. If using self-adhesive felt, remove the protective film gradually as you press the sheet down to avoid air pockets.

Ventilation And Drainage Considerations

A well-ventilated shed roof reduces heat buildup and prolongs the life of the felt. If the shed has a hip or ridge line, consider additional venting above the felt to maintain airflow. Ensure gutters and downspouts are clear or installed where appropriate to manage runoff, though many shed roofs rely on the edge overhang for water shedding. For flat or low-slope sheds, ensure the overhang is sufficient to direct water away from walls and foundations.

Common Mistakes To Avoid

• Using damaged or porous boards as the base, which can deform under heat and moisture.
• Installing felt on a damp surface, which traps moisture and weakens adhesion.
• Skipping the nail sealing step, allowing wind-driven water to penetrate along nail lines.
• Over-stretching the felt, leading to cracks and tears under temperature changes.
• Neglecting to seal around vents, screws, and joints, creating leaks.

Maintenance And Longevity

After installation, inspect the shed roof annually, especially after severe weather. Look for lifted edges, cracks, or worn seams and reseal as needed. Keep gutters clear and check for algae or mold growth, which can degrade the felt surface. If the shed roof experiences repeated leaks, consider thicker felt or adding a protective cap sheet or a roof coating for extra durability. A well-maintained felt roof can last 7-15 years depending on climate and exposure.

Safety Considerations

Work from stable equipment and never work on a wet or icy surface. Use a sturdy ladder, secure footing, and fall protection when necessary. Wear gloves to protect hands from sharp edges and a long-sleeved shirt to guard against contact with roofing cement. Keep tools organized to prevent slips or dropped objects from causing injury.