Replacing shed roof felt is a practical home improvement task that protects the structure from leaks and extends the life of a shed. This guide covers why felt is used, how to choose the right material, and a step-by-step approach for a safe, durable replacement. It covers common pitfalls, tools, materials, and cost considerations to help homeowners decide between DIY and hiring a professional.
What You Need To Know About Shed Roof Felt
Shed roof felt, often made from asphalt-impregnated felt or newer modified bitumen, provides a moisture barrier between the roof deck and shingles or metal cladding. Over time, exposed felt can deteriorate due to UV exposure, temperature swings, and critter activity. Replacing it sooner rather than later prevents roof deck rot and leaks. When choosing felt, look for performance ratings such as tear resistance, age, and compatibility with the chosen roofing surface. For sheds with flat or low-slope roofs, felt underlayment is typically installed as a continuous layer to shed water effectively.
Tools And Materials You’ll Need
- Replacement roof felt (asphalt-saturated felt or synthetic underlayment)
- Roofing nails or cap nails (galvanized)
- Hammer or stapler (depending on fastener type)
- Utility knife
- Chalk line
- Measuring tape
- Roofing adhesive tape or sealant (optional for edges)
- Tin snips or scissors (for metal edges)
- Ladder safety gear and fall protection as needed
- Protective gloves and eye protection
Assess The Roof And Plan The Replacement
Begin by inspecting the shed roof to determine its slope, decking condition, and any signs of rot or damage. If the roof deck shows widespread rot, it may require replacing damaged boards before felt installation. Measure the roof area to estimate material quantities, adding a 10% waste factor for cuts and mistakes. Decide on felt type: traditional asphalt-saturated felt is common and cost-effective, while synthetic underlayment offers higher tear resistance and longer service life. For most garden sheds with a shallow pitch, underlayment should extend over eaves and into gutters or drip edges to direct water away from the structure.
Preparation And Safety Steps
Set up a stable, secure ladder and wear safety gear. Remove any existing shingles or overlapping layers if present, and clear debris from the deck. Dry, clean surfaces ensure proper adhesion and nail seating. If the shed is in a high-wind area or has variable weather, consider delaying installation for a calm, dry day. Ensure adequate ventilation in any attic space if the shed has one to prevent moisture buildup during the process.
Step-By-Step: Replacing The Shed Roof Felt
- Remove Old Felt: Start at one eave and lift the edge of the existing felt. Use a flat pry tool to detach nails or staples, working toward the opposite side. Dispose of old felt properly.
- Inspect Roof Deck: Check for cracked or rotten boards. Replace damaged sections with matching plywood or OSB. Sand rough edges to create a smooth surface for the new underlayment.
- Measure And Cut: Roll out the new felt across the deck. Use a chalk line to mark straight edges and cut slightly larger than the deck area to account for edges and overlaps.
- Install The Underslayment: Start at the bottom edge, unroll the felt, and align it with the eave. For asphalt-saturated felt, position so the grain runs horizontally along the roof. Leave a slight overhang at the drip edge.
- Nailing Or Securing: Fasten the felt along the bottom edge first, then secure the rest with nails or staples at regular intervals. Use a nail gun or hammer, ensuring nails are driven flush but not through the deck. Space nails to avoid tearing the felt on folds.
- Sealing Edges: Overlap seams by at least 4-6 inches if using multiple sheets. In critical areas such as overhangs, apply roofing tape or sealant to edge joints to improve water resistance.
- Finish Edges And Vents: Trim excess material at ridges, hips, and around any vent pipes. Seal around protrusions with compatible sealant to prevent water intrusion.
- Inspection And Cleanup: Inspect the installation for loose sections or gaps. Clear debris from gutters and verify edge alignment. Clean and store tools and dispose of waste.
Common Mistakes And How To Avoid Them
- Incorrect overlap: Insufficient overlap can lead to leaks. Ensure proper seam alignment and adequate overlap.
- Overdriving nails: Driving nails too deep can damage the deck and cause bulges or tears in the felt. Drive nails flush, not through.
- Ignoring deck condition: A rotten deck defeats the purpose of underlayment. Replace damaged boards before felt installation.
- Choosing the wrong felt: Synthetic underlayment offers higher durability but may require different installation methods. Match the product to the roof type.
Maintenance Tips After Replacement
Periodically inspect the shed roof after installation, especially after heavy rain or wind events. Look for lifted edges, gaps, or signs of wear along seams and edges. Clear debris from gutters to prevent water buildup near the edges. Re-seal joints and edges with compatible sealant as recommended by the manufacturer. Consider adding a protective top layer, such as metal flashing, over high-wear zones to extend the felt’s life.
Estimating Cost And Time
Costs vary by material, shed size, and regional labor rates if hiring a pro. A DIY project typically costs less than professional installation, with material costs ranging from modest to moderate depending on the choice between traditional felt and synthetic underlayment. Labor time for a typical shed roof replacement ranges from half a day to a full day for moderate-sized structures. For larger sheds or complicated rooflines, plan for extra time and consider seeking help for handling and safety on the ladder.
DIY Or Hire A Pro: Making The Right Choice
DIY replacement suits homeowners with basic carpentry skills and comfortable use of ladders. It offers significant cost savings and a sense of accomplishment. However, pro installation ensures exact sealing, weatherproofing, and a warranty-backed installation, which can be worth it for sheds that store valuable equipment or that sit in high-wind zones. When choosing a contractor, verify licenses, insurance, and references, and ask about the specific underlayment product and warranty terms. For straightforward sheds, a well-executed DIY project can deliver durable results and long-term protection.
Frequently Asked Questions
- Can I replace shed roof felt without removing old shingles? Yes, but ensure the deck is clean and intact before laying new felt for proper adhesion.
- What type of underlayment should I use for a metal shed roof? Synthetic underlayment often performs better under metal roofs due to higher tear resistance and weather resistance.
- How long does shed roof felt last? With proper installation and maintenance, felt underlayment can last 5-10 years for traditional asphalt felt; synthetic underlayment may last longer, depending on climate and sun exposure.