How to Install Roof Flashing Against a Brick Wall

Installing roof flashing where the roof meets a brick wall is a critical task for preventing water infiltration, which can lead to structural damage, mold growth, and costly repairs. Proper flashing directs water away from vulnerable joints, ensuring the longevity of both the roof and the masonry. This guide provides a thorough exploration of techniques, materials, and best practices drawn from industry standards, tailored for homeowners and contractors working with brick structures.

Understanding the Role of Roof Flashing

Roof flashing serves as a protective barrier at junctions where roofing materials meet vertical surfaces like brick walls. These areas are prone to water accumulation due to wind-driven rain and gravity. Without effective flashing, moisture seeps into the roof deck or behind the brick veneer, compromising insulation, framing, and interior finishes.

Key types include step flashing for roof-to-wall transitions, counter flashing embedded in the wall, and base or apron flashing at the bottom. Each component works in tandem to create multiple layers of defense. Building codes, such as those from the International Residential Code (IRC), mandate proper installation to meet weather resistance standards.

Essential Materials and Tools

Selecting high-quality materials is foundational to a successful installation. Common choices include galvanized steel, aluminum, or copper for durability and corrosion resistance. Aluminum is lightweight and cost-effective for most residential applications, while copper offers superior longevity in harsh climates.

• Flashing metal: 26-28 gauge aluminum or 16 oz. copper sheets.
• Underlayment: Self-adhering ice and water shield membrane (e.g., synthetic rubberized asphalt).
• Sealants: Polyurethane or butyl-based roofing cement; avoid silicone for metal interfaces.
• Fasteners: Roofing nails (1.25-inch, galvanized), masonry screws for counter flashing.

Tools required encompass tin snips for cutting, a mallet for bending, angle grinder with diamond blade for mortar joints, hammer, caulk gun, and safety gear (gloves, goggles, harness for steep roofs).

Preparation Steps for Optimal Installation

Begin with a thorough assessment of the existing roof and wall. Remove old shingles and deteriorated flashing to expose the deck and brick. Clean surfaces meticulously, grinding away old caulk or mortar residue to ensure adhesion.

Install ice and water shield first: Roll it over the roof deck and extend it 3-6 inches up the brick face. This membrane seals nail penetrations and provides a slip sheet for differential movement between roof and wall.

Measure precisely: Account for roof pitch, wall height, and shingle overlap (typically 5-8 inches up the wall). For corners, fabricate custom L-shaped pieces by cutting and bending standard step flashing.

Step-by-Step Installation Process

1. Base Flashing and Kickout Diverter

At the roof-wall junction’s base, position a kickout flashing (diverter) snug against the wall, angled to direct water into the gutter. Secure with roofing cement and one nail per end into the deck only—not the wall—to allow movement.

2. Step Flashing Integration

Work upslope with shingle installation. Place the first step flashing over the starter strip, extending under the first course shingles. Nail only to the roof deck (two nails max, top edge). Alternate shingles and flashing pieces, ensuring each flashing laps the one below by 2 inches.

For straight walls without corners: Overlap successive pieces by 4 inches, sealing joints with mastic.

3. Handling Wall Corners

Create corner flashing by notching a 45-degree triangle from standard L-flashing, then bending tightly. Install the corner piece first, nailing to deck. Follow with adjacent step flashings, applying sealant under overlaps.

4. Counter Flashing for Brick Walls

Grind a reglet (1/2-inch deep groove) into the mortar joint 1-2 inches above the step flashing top. Insert counter flashing legs: bottom over step flashing (2-inch overlap), top into reglet. Secure with masonry nails or screws, then seal the reglet with polyurethane caulk.

For multi-story or dormer walls, ensure counter flashing rises at least 8 inches above the roof plane.

5. Vent and Chimney Transitions

Around vents, bed boot flashing in sealant over shingles, nailing to deck. Cut shingles to wrap the base. For chimneys, custom-bend base flashing to wall width, install step flashing around perimeter, then counter flash into chased mortar joints.

Advanced Techniques for Challenging Scenarios

Retrofit installations on existing brick walls often require partial veneer removal to tuck underlayment behind masonry. Use Z-bar through-wall flashing with weeps every 24 inches to drain incidental wall moisture.

In high-wind zones, add metal closure strips at flashing ends and use adhesive seam tape for membrane overlaps. For steep pitches (>6:12), reinforce with additional nailing rows.

Safety Protocols and Best Practices

Always prioritize safety: Use fall protection harnesses, secure ladders, and work with a partner on pitches over 4:12. Avoid installing in wet or freezing conditions, as sealants fail below 40°F.

• Never nail flashing to both roof and wall—risks cracking from expansion.
• Seal only overlaps and reglets; caulk is supplemental, not primary.
• Inspect annually for uplift, corrosion, or gaps.

Common Mistakes and Troubleshooting

Avoid these pitfalls:

• Inadequate overlap: Ensures water bypass; always 2-4 inches.
• Over-nailing: Causes leaks; limit to specified points.
• Poor wall prep: Loose mortar leads to counter flashing pop-out.

For repairs: Start from the bottom, replacing pieces upslope. If base flashing fails, remove overlying shingles.

Maintenance for Longevity

Regular inspections post-storm reveal issues early. Clean gutters to prevent backflow. Reapply sealant every 5-7 years. Copper flashings last 50+ years; aluminum 20-30 with proper install.

Frequently Asked Questions (FAQs)

What is the best material for flashing against brick?

Aluminum for cost-effectiveness; copper for premium durability in corrosive environments.

Can I install flashing over existing stucco or brick?

No—remove veneer at the junction for code-compliant underlayment integration.

How much does professional installation cost?

$5-15 per linear foot, varying by complexity and materials.

Is kickout flashing always necessary?

Yes, at wall-roof terminations to divert water from gutters.

What sealant works best for counter flashing?

Polyurethane like Tremco Vulkem for flexibility and adhesion.