Roof Flashing: Types, Installation, and Repairs

Flashing might not be the most glamorous roofing component, but it's absolutely critical. These thin pieces of metal or other waterproof material seal the gaps where your roof meets walls, chimneys, vents, and other penetrations. When flashing fails, leaks follow. Here's everything Florida homeowners need to know about roof flashing.

What Is Roof Flashing?

Roof flashing is waterproof material installed at transitions and penetrations to direct water away from vulnerable areas. Think of it as the weatherproofing at every 'edge case' on your roof—wherever roofing materials alone can't form a complete seal.

Why Flashing Matters

Even the best roofing materials can't seal every gap:

• Shingles end at walls and chimneys
• Vents and pipes penetrate the roof surface
• Valleys channel water at high volume
• Skylights create large rectangular penetrations

Without proper flashing, water would enter at every one of these points. As we note in our roof leak causes guide, flashing failure is the number one source of roof leaks.

Flashing Materials

Several materials are used for flashing, each with pros and cons:

Aluminum:

• Lightweight and easy to work with
• Doesn't rust (but can corrode)
• Less expensive than copper
• Can react with cedar or treated lumber (galvanic corrosion)

Galvanized Steel:

• Strong and durable
• Can rust when zinc coating wears
• Good value for most applications
• Common on residential roofs

Copper:

• Premium appearance (develops patina)
• Extremely long-lasting (50+ years)
• Higher cost
• Excellent for visible applications

Lead:

• Traditional material, very malleable
• Excellent for complex shapes
• Environmental concerns limit modern use
• Still used in some restoration work

Rubber/EPDM:

• Flexible, easy to install
• Used for vent pipe boots
• Degrades in UV light over time
• Good for 10-15 years typically

Types of Roof Flashing

Step Flashing

Where Used: Where roof slopes meet vertical walls (such as dormers or second-story walls)

How It Works:

• Individual L-shaped pieces installed with each course of shingles
• Each piece overlaps the one below
• Creates a stair-step pattern up the wall
• Works with counter flashing or siding for complete seal

Common Problems:

• Improper installation (pieces too short)
• Sealant failure over time
• Siding damage exposing flashing
• Missing pieces from wind or repairs

Counter Flashing

Where Used: Over step flashing and base flashing, typically at chimneys and masonry walls

How It Works:

• Embedded into mortar joints or reglets
• Covers the top of step flashing or base flashing
• Prevents water from getting behind the primary flashing

Common Problems:

• Mortar deterioration releasing flashing
• Improper reglet depth
• Sealant failure at top edge

Base Flashing (Apron Flashing)

Where Used: At the bottom of walls, chimneys, and other vertical surfaces

How It Works:

• L-shaped flashing with one leg under shingles
• Other leg bent up against vertical surface
• Works with counter flashing for complete protection

Common Problems:

• Corrosion at bend
• Lifting from expansion/contraction
• Debris accumulation behind flashing

Valley Flashing

Where Used: Where two roof slopes meet forming a valley

How It Works:

• Open metal valley: Visible metal channel
• Closed cut valley: Flashing under shingles
• Woven valley: No metal, shingles woven together

Florida Recommendation:

Open metal valleys are generally preferred in Florida because:

• Better handling of heavy rainfall
• Easier debris flow
• Easier to inspect and maintain
• Longer lasting

Drip Edge

Where Used: Along roof edges (eaves and rakes)

How It Works:

• Directs water away from fascia and into gutters
• Prevents water from wicking under roofing
• Required by Florida Building Code

As discussed in our building codes guide, drip edge is mandatory in Florida.

Vent Pipe Flashing (Pipe Boots)

Where Used: Around plumbing vent pipes

How It Works:

• Rubber or metal collar fits around pipe
• Base slides under upper shingles, over lower shingles
• Creates watertight seal around penetration

Common Problems:

• Rubber deterioration from UV exposure
• Cracking around the collar
• Typical lifespan: 10-15 years in Florida

Skylight Flashing

Where Used: Around skylights

How It Works:

• Typically a complete kit with all four sides
• Integrates with step flashing on sides
• Saddle or cricket above to divert water

Skylight flashing is complex. See our skylight leak guide for more details.

Chimney Flashing

Where Used: Where chimney meets roof

How It Works:

• Multi-component system
• Step flashing on sides
• Base flashing at front
• Cricket or saddle at back (for chimneys wider than 30 inches)
• Counter flashing overlaps all

Why Chimneys Are Complex:

• Four different planes to waterproof
• High-volume water flow in heavy rain
• Thermal expansion from heat
• Mortar deterioration over time

Flashing Installation Best Practices

Proper Overlap

All flashing must overlap correctly:

• Upper pieces over lower pieces
• Minimum 3-4 inch overlap typically
• Roof pitch affects required overlap
• Water should never have opportunity to flow behind flashing

Sealant Usage

Sealant supplements but doesn't replace proper installation:

• Use compatible sealants (polyurethane for most applications)
• Apply under flashing edges where appropriate
• Don't rely on sealant alone—it fails over time
• Quality sealants last 5-10 years; flashing should last longer

Fastening

Proper fastening prevents lifting:

• Nail through upper portion (hidden by overlapping material)
• Avoid nailing through exposed areas
• Allow for thermal expansion
• Use compatible metals to prevent galvanic corrosion

Integration with Roofing

Flashing must work with roofing materials:

• Install in proper sequence with shingles
• Some flashing goes under shingles, some over
• Never expose fasteners on shingle-covered portions
• Follow manufacturer specifications

Common Flashing Problems

Corrosion and Rust

Causes:

• Age and weather exposure
• Galvanic corrosion (dissimilar metals)
• Standing water
• Salt air (coastal Florida)

Signs:

• Visible rust stains on roof
• Deteriorated metal edges
• Holes in flashing

Lifted or Separated Flashing

Causes:

• Thermal expansion and contraction
• Wind damage
• Improper installation
• Age-related sealant failure

Signs:

• Visible gaps at flashing edges
• Flashing pulling away from surface
• Bent or lifted metal

Deteriorated Sealant

Causes:

• UV degradation
• Age (5-10 years typical)
• Temperature cycling
• Use of improper sealant type

Signs:

• Cracked or brittle sealant
• Gaps where sealant has pulled away
• Water stains below flashing

Improper Previous Repairs

Common Problems:

• Roofing cement slathered over everything
• Flashing installed out of sequence
• Incompatible materials used
• Exposed fasteners

The Roofing Cement Problem:

Many DIY repairs involve excessive roofing cement. While it works temporarily, it:

• Dries and cracks over time
• Makes proper repair more difficult later
• Hides underlying problems
• Is not a substitute for proper flashing

Flashing Repair and Replacement

When to Repair vs. Replace

Repair When:

• Sealant has failed but metal is sound
• Minor lifting that can be resecured
• Small gaps or separations

Replace When:

• Metal is corroded or has holes
• Multiple repair attempts have failed
• Flashing is outdated design
• During roof replacement (always)

DIY Considerations

Some flashing maintenance is manageable:

• Resealing pipe boots
• Applying sealant to minor gaps
• Cleaning debris from valleys

Leave to Professionals:

• Chimney flashing (complex multi-piece)
• Step flashing requiring siding removal
• Valley flashing replacement
• Any work requiring roof material removal

Cost of Flashing Repairs

Florida flashing repair costs:

• Sealant application: $100-$300
• Pipe boot replacement: $150-$350
• Step flashing repair: $300-$800
• Chimney reflashing: $500-$1,500+
• Valley reflashing: $500-$1,200

Flashing During Roof Replacement

When getting a new roof, all flashing should be addressed:

What Should Be Replaced

• All pipe boots and vent flashing
• Valley flashing
• Drip edge
• Any visibly deteriorated step flashing

What Can Sometimes Be Reused

• Chimney counter flashing (if embedded in good mortar)
• High-quality copper flashing in good condition
• Recently installed premium flashing

Questions to Ask Your Contractor

• What flashing is included in the quote?
• What type and gauge of metal?
• Will all pipe boots be replaced?
• Is chimney reflashing included?
• What warranty covers flashing?

Florida-Specific Flashing Considerations

Wind Resistance

Florida's high winds require:

• Secure fastening
• Proper edge sealing
• Wind-resistant installation methods
• Compliance with Florida Building Code

Hurricane Preparedness

After hurricanes, check flashing for:

• Wind lifting
• Debris impact damage
• Sealant failure from pressure changes
• Missing or displaced components

See our post-storm checklist for complete inspection guidance.

UV and Heat

Florida's intense sun affects flashing:

• Sealants degrade faster
• Rubber boots fail sooner
• Thermal expansion is significant
• Light-colored metals preferred where visible

The Bottom Line

Flashing is critical infrastructure for your roof. Proper installation and maintenance prevents the majority of roof leaks. If you notice any signs of flashing problems—stains below roof penetrations, visible gaps, or deteriorated materials—address them promptly before water damage occurs.

At Pro Specialty Services, we pay careful attention to flashing on every roofing project. During inspections, we examine all flashing points. During replacements, we use quality materials and proper installation techniques. Contact us for a roof inspection if you're concerned about flashing on your Florida home.