Roll roofing offers a cost-effective, durable solution for low-slope roofs on sheds, porches, and small structures. This guide provides practical, step-by-step instructions, best practices for preparation, material selection, and installation techniques to help homeowners and builders achieve a secure, long-lasting roof. It covers surface preparation, underlayment, fasteners, seam detailing, flashing, and maintenance tips to ensure a watertight result with proper adherence to safety standards.
What Roll Roofing Is And When To Use It
Roll roofing is a asphalt-based product sold in narrow rolls that are laid across the roof deck and joined at seams. It is specifically designed for low-slope or flat roofs, typically with slopes of 2:12 or greater, where a lightweight, affordable option is preferable. It is commonly used on sheds, garages, carports, porch roofs, and other non-heritage structures where ease of installation and repair access are priorities.
Key Materials And Tools
Having the right materials streamlines installation and reduces call-backs. Essential items include:
- Roll roofing sheets (asphalt-modified bitumen, typically 36 or 39 inches wide)
- Roofing felt or underlayment (if required by local code or manufacturer)
- Adhesive or roofing cement for lap joints
- Roofing nails with large heads and plastic caps or cap nails
- Seam tape or asphalt-based seam sealant for exposed seams
- Roofing knife or utility knife for cuts
- Chalk line, measuring tape, straightedge, square
- Roofing hammer or nail gun with countersink
- Caulking gun and exterior-grade sealant (for flashing and penetrations)
- Safety gear: gloves, eye protection, non-slip footwear
Always verify manufacturer specifications for the chosen roll roofing product, including recommended underlayment, nail spacing, and seam sealing methods.
Surface Preparation
Proper prep is essential for a durable installation. Begin with a clean, dry, smooth deck free of protrusions, nails, and debris. If the roof has existing shingles or debris, remove them and repair damaged boards. Check for sagging or damaged decking and replace as needed to maintain a flat, uniform surface. Ensure adequate ventilation and ensure the roof edges are straight and true to avoid misaligned seams. A straight edge or level can help verify the deck is flat before laying the first row.
Underlayment And Deck Preparation
Some roll roofing systems require a specific underlayment, while modern products may be installed directly onto clean decking. If underlayment is used, install per manufacturer instructions, ensuring seams are properly sealed. In colder climates or areas with high moisture, a breathable underlayment may help manage moisture while preserving the roof’s integrity. Never install roll roofing over protrusions without flashing; these must be shielded and sealed to prevent leaks.
Layout And Edge Detailing
Accurate layout saves time and improves water shedding. Start by measuring the roof width and determining the number of full sheets across the deck. Snap chalk lines to indicate the first course and the direction of the rolls. For edge detailing, ensure the eave overhang is consistent and secure the lower edge with fasteners placed per the manufacturer’s spacing guidelines. The top edge should align with the roof ridge, and any overhang should be trimmed for a clean finish. Masking or masking tape may help protect edges during installation.
Roll Roofing Installation Steps
The following steps outline a typical installation for a standard asphalt roll roofing system:
- Position the first roll along the eave line with the exposed edge facing outward and the roll centered across the width of the roof.
- Unroll slowly and align the roll with the chalk line, ensuring it lies flat without wrinkles or air pockets.
- Nail the lower edge along the eave using galvanized nails spaced according to the manufacturer’s guidance, typically 6–8 inches apart along the lower edge.
- Continue laying rolls across the width, ensuring laps overlap by the specified amount (usually 3 inches for standard but check product instructions).
- At each seam, apply seam adhesive or sheet sealant along the upper edge and press firmly to bond.
- Work toward the roof peak, overlapping rolls in the recommended direction to shed water away from the interior space.
- Trim excess material at the ridge line or perimeter with a sharp knife, ensuring a tight fit and clean edge.
When nails are used, countersink them slightly and seal around each nail with sealant to prevent water intrusion. Be mindful of wind hold-down requirements; in high-wind regions, more fasteners or specialized clips may be recommended.
Seam Sealing And Flashing
Seam sealing is critical to prevent leaks. Apply seam tape or asphalt-based sealant along exposed seams as directed by the manufacturer. Install flashing around roof penetrations, including vent pipes, skylights, and chimneys, using compatible sealants and fasteners. Fold flashing down over the roll roofing edge where possible and seal the base to the deck with appropriate sealant. At roof-to-wall transitions, use step flashing or a continuous metal flashing to redirect water away from the interior space.
Ventilation, Insulation, And Temperature Considerations
Roll roofing performs best when installed in mild, dry conditions. Avoid installation in extreme heat or when decks are wet or frozen. Adequate ventilation helps prevent moisture buildup and prolongs roof life. Insulation beneath the deck contributes to temperature regulation and comfort in the structure. In warmer climates, consider reflecting surfaces or light-colored roll roofing to minimize heat absorption and extend longevity.
Maintenance And Inspection
Regular inspection helps catch issues before they become leaks. Check for damaged seams, fastener loosening, and flashing deterioration after severe weather. Clean debris from gutters and eaves to prevent water backup. If a seam begins to lift, re-seal it promptly and consider re-nailing along the edge if necessary. Roll roofing typically has a shorter lifespan than asphalt shingles or metal roofing, so plan for periodic maintenance or replacement intervals based on climate and wear.
Safety And Best Practices
Safety is paramount during installation. Use a sturdy ladder, secure fall protection where required, and work with a partner if possible. Keep a clear work area, remove trip hazards, and wear appropriate PPE. Follow all local building codes and manufacturer instructions, especially regarding underlayment, nail spacing, and seam sealing. If the roof design includes complex edges or multiple penetrations, consult a professional roofer to ensure a leak-free result.
Common Pitfalls And How To Avoid Them
Common issues include improper seam sealing, insufficient fasteners at edges, and failing to maintain a clean, dry surface during installation. To avoid these problems, conduct a thorough deck inspection, follow manufacturer guidelines precisely, and ensure the installation window is dry and moderate in temperature. Practice precision with nail placement and edge alignments to prevent wind uplift and leaks.
Re-Roofing And Repair Considerations
When replacing existing roll roofing, remove all old material and inspect the substrate for damage. If the deck shows signs of rot or structural issues, address these before applying new material. For repairs, patch small damaged areas with matching roll roofing material or sealant and reseal all seams and edges to restore continuity. Consider upgrading to a higher-performance roll roofing product if the current system demonstrates frequent leaks or wear.
Why Choose Roll Roofing
Roll roofing remains an economical option for low-slope roofs with straightforward layouts. It offers quick installation, simple maintenance, and effective waterproofing when installed correctly. It is well-suited for outbuildings, garden sheds, and workshops where budget and speed are key considerations, while still providing reliable protection against precipitation when properly applied.