Rolled roofing installation is a popular and cost-effective solution for low-slope or flat roofs on structures like sheds, garages, workshops, and even certain residential additions. Composed of long rolls of asphalt-impregnated material topped with mineral granules, this roofing type is known for its durability, weather resistance, and relative ease of installation compared to other roofing systems. While it may not offer the aesthetic appeal of dimensional shingles, its functional benefits make it an excellent choice for outbuildings and budget-conscious projects. A successful installation hinges on proper preparation, correct technique, and attention to detail.
Before embarking on a rolled roofing installation project, the first and most critical step is to assess the existing roof deck. The substrate must be clean, dry, solid, and smooth. Any old roofing material should be completely removed. Inspect the deck for any signs of rot, soft spots, or damage to the underlying sheathing, typically made of plywood or oriented strand board (OSB). All compromised sections must be cut out and replaced to ensure a stable foundation. Protruding nails should be driven down, and the entire surface must be swept clean of all debris, dust, and dirt. A weak or uneven deck will lead to problems with the new roof, no matter how well the rolled roofing is applied.
Gathering the right tools and materials beforehand streamlines the installation process significantly. Essential items include the rolled roofing itself, specialized roofing nails with large, galvanized heads, and a high-quality roofing cement or lap adhesive. A utility knife with plenty of sharp blades is indispensable for making clean cuts. You will also need a chalk line for snapping straight guidelines, a sturdy hammer or a roofing nail gun for faster nailing, a roofing shovel for tear-off, a pry bar, a tape measure, and a sturdy ladder. For safety, never work on a roof without proper fall protection, such as a harness system, and wear non-slip shoes.
The installation process begins with the application of drip edge flashing. This metal strip is installed along the eaves (the lower edge of the roof) and rakes (the sloped edges) to direct water away from the fascia board and into the gutters, protecting the underlying wood from water damage. The drip edge should be secured with roofing nails every 8 to 10 inches along the top flange. An ice and water shield, which is a self-adhering waterproofing membrane, is highly recommended, especially in colder climates. It should be applied over the drip edge along the eaves, extending up the roof at least two feet from the inside wall line to prevent water infiltration from ice dams.
With the preparatory layers in place, you can begin laying the rolled roofing. Start at the eaves and work your way up towards the roof’s peak. Unroll the first sheet along the entire length of the eave, ensuring it overhangs the drip edge by about 1/4 to 3/8 of an inch. This slight overhang is crucial for proper water drainage. Secure the roll by nailing it along the top edge. Use the chalk line to snap a guideline for the nailing pattern, which is typically a straight line about 2 to 3 inches down from the top edge of the roll. Nails should be spaced approximately 12 inches apart along this line. Then, nail along the bottom edge and across the entire field of the sheet in rows, following the manufacturer’s specified nailing pattern, which is often a grid of 4 to 6 inches.
The subsequent course of rolled roofing must overlap the first one to create a watertight seal. The standard overlap is 2 to 4 inches for products with no granular surface in the overlap area, or 6 inches for products that have granules throughout. Before laying the next course, apply a 3-inch-wide band of roofing cement along the top edge of the previously installed sheet, just below the nailing line. This cement acts as an additional sealant for the lap joint. Carefully unroll the second course, aligning it with your chalk lines, and press it firmly into the wet cement. Then, nail it down using the same pattern, ensuring the nails penetrate through both layers of roofing material at the overlap.
When you reach features like roof hips or ridges, special techniques are required. For a hip, you will need to cut the rolled roofing material to fit the angle. A common method is to cut a sheet lengthwise down the middle and fold each half over the hip. Apply roofing cement to the hip line, place the material, and nail it securely. For the ridge cap, cut sections of rolled roofing approximately 12 inches wide and long enough to span the ridge. Fold these pieces evenly over the ridge, cement and nail them down, with each successive piece overlapping the previous one by several inches to shed water effectively. Always seal all nail heads and the edges of these caps with a dab of roofing cement.
Proper flashing around roof penetrations, such as vent pipes, is non-negotiable for a leak-free roof. The best practice is to use pre-formed rubber boot flashings that fit snugly around the pipe. Slide the boot over the pipe and position it so its flange lies flat on the roof deck. Then, install the rolled roofing up to the pipe. Cut a slit in the material to fit around the pipe, and carefully seal the edges with roofing cement, integrating the material with the boot’s flange. The base of the boot should then be nailed and sealed with cement as well. Never rely on cement alone to seal a pipe penetration; a proper flashing boot is essential.
Despite its straightforward nature, several common mistakes can compromise a rolled roofing installation. One of the most frequent errors is nailing incorrectly. Nails should be driven straight so the head is flush with the surface of the roofing material, not sunk in, which can tear the fabric, or left protruding, which can snag and lift. Another critical mistake is working in wet or cold conditions. The material becomes brittle in cold weather and can crack, while moisture trapped beneath the layers will lead to blisters and premature failure. Finally, insufficient overlap or failure to apply the lap sealant correctly are direct invitations for leaks.
Once the installation is complete, a thorough cleanup and inspection are vital. Walk the entire roof surface, checking for any loose edges, unsealed nails, or wrinkles in the material. Pay close attention to all flashings, overlaps, and penetrations, applying additional cement wherever a seal looks imperfect. Clean up any spilled cement and dispose of all old materials and packaging properly. With proper care and maintenance, including periodic inspections and clearing of debris, a correctly installed rolled roof can protect your structure for 10 to 15 years or more, providing dependable and affordable shelter from the elements.
In summary, a successful rolled roofing installation is a manageable DIY project for a confident homeowner, but it demands meticulous preparation and execution. The key steps involve:
- Ensuring a sound, clean, and dry roof deck.
- Installing drip edge and ice/water shield for critical protection.
- Applying the rolls from the eave upward with consistent, sealed overlaps.
- Properly flashing hips, ridges, and penetrations.
- Avoiding common pitfalls like incorrect nailing and working in poor weather.
By following these guidelines and adhering to the manufacturer’s instructions for your specific product, you can achieve a professional-looking, durable, and watertight roof that will serve you well for many years.