How to Install Composite Roofing Shingles

Installing composite roofing shingles is a manageable project for homeowners with basic carpentry skills and the right materials. Composite shingles, also known as asphalt shingles, provide an affordable and durable roofing solution that protects your home from the elements. This guide walks you through every stage of the installation process, from roof preparation to the final finishing touches.

Understanding Your Roofing System

A complete composite roofing system consists of three essential layers working together to protect your home. The foundation begins with roof sheathing, typically made of plywood panels that are nailed to the roof rafters. This structural layer provides the base upon which all other components rest and gives roofers a safe walking surface during installation.

Above the sheathing lies a synthetic water-resistant underlayment, which acts as a secondary moisture barrier. This underlayment is critical for preventing water infiltration, especially during heavy rains or if shingles become damaged. The final layer consists of the composite shingles themselves, which provide the visible protection and aesthetic appeal of your roof.

Pre-Installation Preparation

Checking Roof Slope Requirements

Before beginning installation, verify that your roof slope meets minimum standards. Composite shingles should never be installed on roof slopes less than 2:12 (meaning a 2-inch rise for every 12 inches of horizontal run). For slopes between 2:12 and 4:12, special underlayment products may be required to ensure proper water management. Steeper slopes, 4:12 and above, follow standard installation procedures.

Installing the Underlayment

Proper underlayment installation is foundational to roof longevity. Follow these key steps:

• Install underlayment parallel to the eaves, ensuring it overhangs the edge by 1/4 inch to 3/8 inch
• Position fasteners 2 inches from the deck edge, spaced 12 inches on center along the lower edge
• Maintain a 2-inch overlap parallel to the eaves and a minimum 4-inch end lap running parallel to the rake (sloped edge)
• Stagger underlayment end laps 6 feet apart from adjacent courses to prevent water seepage at joints
• Install corrosion-resistant drip edge over the underlayment at the rake and beneath the underlayment at the eaves for enhanced water protection

Atlas recommends applying shingles the same day as underlayment installation to avoid wetting and wrinkling of the underlayment material.

Setting Up Chalk Lines and References

Strike chalk lines horizontally across the roof to guide shingle placement and ensure straight, even courses. These reference lines are particularly important when working across large roof areas, as they help maintain consistent alignment and proper exposure throughout the installation.

Installing the Starter Course

The starter course forms the foundation for all subsequent rows of shingles. Begin by positioning starter shingles along the eaves, with the adhesive strips facing upward. If using pre-cut starter shingles with perforations, fold along the indicated lines to separate sections.

Cut the first starter shingle in half and position it at the lower left corner of the roof. The granule side should face upward, and the shingle should align with the drip edge. Continue across the eaves with full-length starter shingles, butting them loosely together to allow for minor expansion without buckling. Secure the starter course with fasteners spaced appropriately according to manufacturer specifications.

Applying the Main Shingle Courses

First Course Installation

Lay the first full course directly over the starter course, beginning at the same lower corner where you started the starter course. Ensure shingles are flush with the edges of the starter course on both the eave and rake sides. Fasten each shingle with four nails placed as specified by the manufacturer, typically in a line above the cutouts of the shingle below.

Building Subsequent Courses

To achieve proper offset and prevent vertical alignment of seams, each course must be staggered. The standard pattern involves trimming increasing amounts from successive courses:

• Second course: Trim 10 inches from the left end of the starting shingle
• Third course: Trim 20 inches from the left end
• Fourth course: Trim 30 inches from the left end
• Fifth and subsequent courses: Repeat the offset pattern established by the first four courses

Each trimmed shingle should overhang the rake edge by 1/4 inch to 3/4 inch, maintaining a uniform appearance while ensuring adequate coverage. Continue each course across the roof with full-length shingles, maintaining consistent nailing patterns.

Proper Nailing Technique

Correct nailing is critical for shingle durability and wind resistance. Standard applications require four nails per shingle, placed in a line above the cutouts. In high-wind areas or on steep slopes of 21:12 (60 degrees) or steeper, use six nails per shingle. Position nails to avoid joints or cutouts in the underlying shingle by at least 2 inches.

Some manufacturers recommend applying roofing cement under shingles in high-wind areas. Apply four quarter-sized dabs of ASTM D4586 asphalt roof cement evenly spaced under each shingle, 2 inches above the bottom edge. Press shingles firmly into the cement, but use sparingly to avoid excessive bleeding and potential blistering.

Managing Valleys and Flashing

Open Valley Method

For open valleys (where shingles from opposite sides of the valley meet without overlapping), strike chalk lines 3 inches from the valley center line on each side. As you apply shingles, trim them to these chalk lines. To direct water properly into the valley, cut 2 inches diagonally off the upper corner of shingles adjacent to the chalk line. Set the valley edge of each shingle in a 3-inch-wide band of asphalt plastic cement meeting ASTM D4586 standards, nailing no closer than 6 inches from the valley center line.

Closed Cut Valley Method

The closed cut valley approach involves more complete coverage. Apply a 36-inch-wide ice and water protection product centered in the valley, nailing only 2 inches from the outer edges. Apply all shingles from one side of the valley and across the center for a minimum of 12 inches. On the opposite side, nail a minimum of 6 inches away from the valley center line, striking a chalk line 2 inches from center on the unshingled side. Apply shingles up to this chalk line and trim. Importantly, do not cut the underlying shingle to preserve the waterproofing layer.

Step Flashing at Walls

Where the roof meets vertical walls or chimneys, install step flashing to prevent water intrusion. Place the first piece of flashing atop the starter course at the eave, with the horizontal flange flush with the eave edge and the vertical flange against the sidewall. Fasten the horizontal flange to the roof, then proceed with shingle courses. Place successive step flashing pieces overlapping the previous piece by approximately 2 inches at the point of shingle exposure.

Finishing Hips and Ridges

Hip and ridge finishing provides the final protective layer at the roof’s peaks. Manufacturers offer pre-cut hip and ridge shingles that simplify this process. Separate the pre-cut shingles into three equal pieces along perforated lines, then bend each piece lengthwise to provide equal exposure on both sides of the ridge or hip.

Allow 5 5/8 inches of exposure for each piece and nail 6 inches from the exposed butt edge using two nails positioned 1 inch from each side. Orient the exposed end away from the prevailing wind direction to minimize wind damage. One bundle of pre-cut hip and ridge shingles typically covers approximately 31 linear feet of ridge. Cover exposed nail heads of the final shingle with roofing cement for added weather protection.

Climate Considerations and Special Conditions

Cold Weather Installation

Installing composite shingles in cold weather requires special attention. In temperatures below 50 degrees Fahrenheit, shingle sealant strips do not bond as effectively. Manually seal shingles by applying roofing cement under each shingle as described previously. Additionally, store hip and ridge shingles in a heated area before installation to allow the material to warm and bend more easily without cracking.

High-Wind Areas

Properties in high-wind zones benefit from additional security measures. Use six nails per shingle instead of four, following manufacturer nail line specifications. Apply optional bands of asphalt plastic cement along the rake edges of each course to enhance wind resistance and prevent wind-driven rain infiltration. This extra step significantly improves the roof’s ability to withstand sustained winds and gusts.

Common Installation Mistakes to Avoid

• Improper underlayment overlap and fastener spacing, leading to water infiltration
• Failing to stagger seams adequately between courses, causing water to channel along vertical joints
• Over-fastening shingles, which restricts necessary movement and increases splitting risk
• Applying excessive roofing cement, which can cause blistering as heat builds under the shingles
• Neglecting proper valley installation, allowing water to pool rather than flow
• Installing shingles on insufficient roof slopes, where water cannot drain properly
• Skipping or improperly installing drip edge, allowing water behind the sheathing

Tools and Materials Checklist

Before beginning installation, gather the following essentials:

• Safety equipment: roof harness, ladder, work gloves, and appropriate footwear
• Installation tools: roofing nail gun or hammer, chalk line, utility knife, and measuring tape
• Roofing materials: underlayment, drip edge, starter shingles, composite shingles, roofing cement, and hip/ridge shingles
• Fasteners: corrosion-resistant roofing nails of appropriate length for your sheathing thickness

Frequently Asked Questions

How long does composite shingle installation typically take?

Installation time depends on roof size and complexity. A typical residential roof may take 1-3 days for experienced installers or 3-7 days for careful DIY work. Complex designs with multiple valleys and penetrations require additional time.

Can I install composite shingles over an existing roof?

While some jurisdictions allow re-roofing over existing shingles, removal of the old roof is generally recommended for better inspection of the deck, more accurate nailing, and longer-lasting results.

What is the expected lifespan of composite shingles?

Quality composite shingles typically last 20-25 years under normal conditions, though this varies based on climate, maintenance, and installation quality.

Do I need underlayment if my roof has tar paper?

Modern synthetic underlayment offers superior protection compared to traditional tar paper. Upgrading to synthetic underlayment is recommended for better water resistance and durability.

What warranty considerations should I be aware of?

Manufacturer warranties often require professional installation by certified roofers. DIY installation may void certain warranty protections, so review warranty terms before starting your project.