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Types of Flashings for Shingle Roofs

When it comes to maintaining the integrity and longevity of a shingle roof, proper flashing installation is essential. Flashings play a critical role in directing water away from vulnerable areas, preventing leaks, and ensuring the overall durability of the roofing system.

With various types of flashings available, each designed to address specific roofing challenges, understanding their differences and applications is crucial for homeowners, contractors, and builders alike.

This article delves into the different types of flashings used for shingle roofs, exploring their unique features, benefits, and the critical role they play in safeguarding your home against the elements.

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Types of Flashings for Shingle Roofs

Roof Flashing Sizes

Roof Flashing Sealant Types

Roof Flashing Installation Techniques

How to Install Counter Flashing on a Chimney

How to Install a Roof Plumbing Vent Flashing Boot

Can You Re-use Old Roof Flashing?

When to Repair a Roof Flashing Leak

Signs of Roof Flashing Leaks

Related Reading

Types of Flashings for Shingle Roofs

There are several different types of flashing used on shingle roofs, each with a specific purpose to channel water away from critical areas and prevent leaks.

Here’s a breakdown of the most common types:

Step Flashing… This is the workhorse of shingle roof flashing. It’s made of L-shaped metal pieces that are installed layer-by-layer as the shingles are laid. Each step overlaps the one below, creating a watertight seal. Step flashing is typically used at intersections like chimneys or sidewalls.

Counter Flashing… This flashing works with step flashing for an extra layer of waterproofing. It’s a long piece of metal bent up the wall and tucked under the siding. The step flashing then slides over the top, creating a double seal.

Base Flashing (Apron Flashing) … This type tackles the rake (edge) of the roof and around roof penetrations like skylights. It’s a long piece of metal bent up over the fascia board and down over the top shingles.

Valley Flashing…  This flashing handles the valleys where two roof sections meet. It’s typically W-shaped metal installed over the underlayment and shingle butts, channeling water down the valley to the eaves.

Drip Edge… This flashing is installed along the eaves to prevent water from blowing under the shingles and causing rot. It’s a thin piece of metal bent down over the edge of the fascia board.

Kickout Flashing… This flashing is used on roofs with minimal eaves overhang. It helps direct water away from the fascia board and siding. Kickout flashing is typically a triangular piece of metal installed at the corner where the roof meets the fascia board.

Roof Flashing Sizes

Roof flashing sizes aren’t one-size-fits-all. They depend on several factors, including:

Flashing Type… Different flashings have different size requirements. For example, step flashing needs to be wide enough to cover the shingle exposure (visible portion) and long enough to extend up the wall and underlayment for proper water deflection.

Shingle Type… The size of your shingle exposure will affect the width needed for step flashing and other flashings that interact with the shingles.

Building Codes… Local building codes may have specific size requirements for roof flashing.  It’s important to check with your local building department to ensure your flashing meets code.

Here’s a general idea of sizing for some common flashings:

Step Flashing… Typically 10 inches long and at least 2 inches wider than the shingle exposure. (e.g., 10 x 8 inches for a shingle with a 5 7/8-inch exposure)

Counter Flashing…  Long sheets typically sold in widths ranging from a few inches to a (48 inches). The height of the counter flashing will depend on how far it needs to extend up the wall under the siding.

Base Flashing (Apron Flashing) … Like counter flashing, base flashing comes in long sheets with width options. The width will depend on how far it needs to extend over the fascia board and how much coverage is needed on the shingles.

Valley Flashing… Typically comes in long sheets (like counter flashing) and needs to be wide enough to extend up the roof planes on either side of the valley. Valley flashing also requires an overlap at the center joint (usually 36 inches).

Drip Edge… Available in various widths, with a common size being around ¾ inch.

Roof Flashing Materials

There are several materials commonly used for roof flashing, each with its own advantages and disadvantages.

Here’s a breakdown of the most popular choices:

Galvanized Steel… This is the most common and cost-effective option. Galvanized steel is strong, durable, and resistant to corrosion. It’s readily available and easy to work with for shaping around roof features. However, it can scratch and may not be the most aesthetically pleasing choice for some.

Aluminum… Lightweight and malleable, aluminum flashing is easy to bend and form around complex roof features. It’s also resistant to rust but can dent more easily than steel.  Aluminum flashing may require a special coating if used with concrete or masonry due to potential reactions with alkaline materials.

Copper… A premium choice, copper flashing offers exceptional durability and longevity. It develops a beautiful patina over time, adding a classic aesthetic touch. However, copper is the most expensive option and requires special installation techniques due to its softness.

Stainless Steel… This high-end material offers excellent corrosion resistance and a sleek modern look. Like copper, stainless steel is a more expensive option and requires specialized installation techniques.

Self-Adhering Rubberized Membranes… These membranes are gaining popularity for their ease of installation and watertight seals. They come in rolls and adhere directly to the roof deck, eliminating the need for separate flashing pieces in some applications.  However, their long-term performance compared to traditional metals may not be fully established yet.

Choosing the right flashing material depends on several factors, including:

Budget… Galvanized steel and aluminum are the most budget-friendly options, while copper and stainless steel are more expensive.

Roof Style and Material… Some materials may complement certain roof styles or materials better aesthetically.

Climate… For areas with high humidity or salt spray, copper or stainless steel might be better choices due to their superior corrosion resistance.

Local Building Codes… Some local building codes may have restrictions on certain flashing materials.

Consulting with a qualified roofing contractor is highly recommended to determine the best flashing material for your specific roof. They can consider all the factors involved and recommend the most appropriate and cost-effective option for your needs.

Roof Flashing Sealant Types

There are two main categories of sealants used for roof flashing:

Water-Based Sealants:


– Affordable

– Easier to apply due to thinner consistency

– Less odor and VOCs (Volatile Organic Compounds) making them better for user health


– Less durable than solvent-based options

– May require multiple applications

Solvent-Based Sealants:


– More durable and longer lasting

– Better adhesion to various materials


– More expensive

– Stronger odor and higher VOCs requiring proper ventilation during application

Here’s a breakdown of some common types of roof flashing sealants within these categories:

Silicone… This is a popular and versatile choice for roof flashing due to its excellent adhesion to various materials, including metal, concrete, and asphalt. It offers good UV protection and flexibility to handle movement in the roof. Silicones are typically solvent based for maximum durability.

Polyurethane… This sealant is known for its strong adhesion, flexibility, and good resistance to water and chemicals. It can be used in both water-based and solvent-based formulas. Water-based polyurethane offers easier cleanup but may not be as durable as solvent-based options.

Acrylic… An affordable and water-based option, acrylic sealants are best for small gaps or non-critical areas. They offer good flexibility but may not be as durable or weather resistant as other choices.

Butyl Rubber… This is a self-adhering sealant that comes in tape form. It’s easy to apply and good for small gaps or repairs. However, butyl rubber may not be as durable as poured sealants for long-term applications.

Choosing the right roof flashing sealant depends on several factors:

Material Compatibility… Ensure the sealant adheres well to both the flashing material and the surrounding roof components.

Durability… Consider the climate and potential weather extremes in your area. Opt for a more durable sealant like silicone or solvent-based polyurethane for critical areas.

Ease of Application… Water-based sealants are easier to work with for DIY projects, while solvent-based options might require more experience or proper ventilation.

Project Requirements… Small repairs might be suitable for butyl tape, while larger areas or critical seams might need a poured sealant like silicone.

Roof Flashing Installation Techniques

Roof flashing installation requires proper techniques to ensure a watertight and long-lasting roof.

Here’s a breakdown of some key techniques for common flashing types:

Step Flashing:

1] Install Underlayment… Before laying shingles, ensure proper underlayment is installed at the roof-wall intersection, extending up the wall a few inches.

2] Slide Under Shingles… Slide the first step flashing piece under the starter shingle course at the wall.

3] Fold and Overlap… Fold the flange (leg) of the flashing that goes up the wall over the underlayment. The horizontal flange should extend over the roof deck.

4] Shingle Overlap… Overlap the vertical flange of the step flashing with the course of shingles being laid.

5] Stack and Interlock… As you shingle upwards, slide each new step flashing piece under the shingle course above and interlock it over the flange of the piece below.

Counter Flashing (with Step Flashing):

1] Install Before Siding…Install counter flashing before the siding is applied.

2] Slide Up Wall… Slide the counter flashing up the wall under the siding material.

3] Bend and Overlap Step Flashing… Bend a flange at the top of the counter flashing to create a pocket. Slide the step flashing flanges into this pocket for a double layer of waterproofing.

Base Flashing (Apron Flashing):

1] Fold and Apply Over Fascia… Fold the base flashing to create a flange that goes up against the fascia board. Apply sealant along the joint between the flashing and fascia.

2] Slide Under Shingles… Slide the horizontal flange of the base flashing under the starter shingle course.

3] Shingle Overlap… Overlap the vertical flange of the base flashing with the course of shingles being laid.

Valley Flashing:

1] Center and Overlap… Center the valley flashing over the joint where the two roof sections meet. Ensure enough overlap at the center seam (typically 36 inches).

2] Fold and Secure… Fold flanges up the sides of the valley onto the roof planes. Secure the flashing with nails or staples along the flanges.

3] Shingle Overlap: Overlap the edges of the valley flashing with the shingles on either side of the valley.

Drip Edge:

1] Fold Over Fascia… Fold the drip edge flange to fit over the fascia board.

2] Slide Under Shingles… Slide the drip edge under the starter shingle course.

3] Nail and Seal (Optional) … You can nail the drip edge for extra security and apply sealant along the joint between the drip edge and fascia board (optional).

General Tips:

– Use proper flashing material and thickness as recommended for your specific application.

– Wear gloves and safety glasses when cutting and handling flashing.

– Cut flashing pieces carefully to ensure proper fit around roof features.

– Apply sealant meticulously at all seams and laps for a watertight seal.

– Use appropriate nails or fasteners for the flashing material and roof deck.

– Overlap flashing pieces in the correct direction to channel water away.

– Ensure proper ventilation under metal flashing to prevent moisture buildup.

Remember:  For complex roof flashing or if you’re unsure about any steps, it’s always best to consult a qualified roofing contractor. They have the expertise and experience to ensure your roof flashing is installed correctly for optimal performance and longevity.

How to Install Counter Flashing on a Chimney

Installing counter flashing around a chimney is a crucial step for preventing water leaks. However, it’s also a task that requires attention to detail and proper safety measures.

Here’s a breakdown of the process, emphasizing the importance of professional help:

Why Hire a Professional?

Expertise Matters… Counter flashing installation involves working with mortar, potentially cutting into the chimney, and ensuring a watertight seal. Improper installation can lead to leaks and costly repairs down the road. A qualified roofer has the experience and knowledge for successful counter flashing installation.

General Steps (Informational Only):

Preparation… The work area needs to be prepared. This may involve removing any loose debris around the chimney and covering nearby surfaces to protect them from dust.

Base Flashing Check… A professional will likely inspect the existing base flashing (apron flashing) around the chimney to ensure it’s properly installed and in good condition.

Mortar Work (Caution) … Creating a groove or pocket in the mortar joints of the chimney is often required to insert the counter flashing.  This can be a delicate process, and  improper cutting could damage the chimney. It’s recommended to have a qualified roofer handle this step.

Counter Flashing Installation… The pre-cut counter flashing is then inserted into the groove created in the mortar.  Techniques like using a bead of caulk and proper flashing bends ensure a secure and watertight fit.

Sealing and Finishing… After the counter flashing is secured, a professional will likely apply a sealant along the edges and any gaps to create a complete water barrier.

While this provides a general overview, it’s not intended as a substitute for professional guidance.  Due to the potential safety hazards and the importance of proper installation for preventing leaks, it’s strongly recommended to hire a qualified roofing contractor to install counter flashing on your chimney.

How to Install a Roof Plumbing Vent Flashing Boot

Here’s a general guide on installing a roof plumbing vent flashing boot, but remember, safety is paramount.  This task involves working on a roof and can be dangerous.  If you’re uncomfortable working at heights or lack experience with roofing tasks, it’s best to hire a qualified roofing contractor.


– Roof plumbing vent flashing boot (sized for your vent pipe)

– Roofing nails

– Caulk (optional, depending on the boot type)

– Utility knife

– Tape measure

– Hammer or nail gun

– Safety gear (gloves, safety glasses, fall protection)

Shed Plans


Shingle Disruption… Identify the plumbing vent pipe and the shingles around it.  You’ll need to loosen or remove some shingles to install the flashing boot.

Flashing Boot Installation:

Sizing and Fit… Test fit the flashing boot over the vent pipe to ensure proper size and clearance. You may need to trim the boot slightly for a good fit.

Shingle Adjustment… Carefully loosen or remove enough shingles around the vent pipe to slide the flashing boot base underneath. How many shingles you need to adjust depends on the specific boot design.

Boot Placement… Slide the flashing boot base under the loosened shingles and position it centered around the vent pipe.

Sealing (Optional) … Some flashing boots may have a pre-applied sealant bead. If not, apply a bead of caulk around the base of the boot where it meets the roof deck for additional waterproofing.

Securing the Boot… Using roofing nails, secure the flashing boot flange to the roof deck under the shingles. Ensure the nails penetrate the deck securely but avoid over-driving and damaging the flashing.

Shingle Repositioning… Carefully replace or refasten the loosened shingles over the flashing boot flange. The shingles should overlap the flashing boot flange as designed.

Final Touches… Inspect the installation for any gaps or areas that may require additional sealant. Make any necessary adjustments to ensure a watertight seal.

This is a general guide, and specific steps may vary depending on the type of flashing boot you have. Refer to the manufacturer’s instructions for your specific product.

Can You Re-use Old Roof Flashing?

Whether you can reuse old roof flashing depends on its condition.

Here’s a breakdown of the factors to consider:

Reusability Criteria:

Condition… The most critical factor is the condition of the flashing. If the flashing shows any signs of damage like rust, corrosion, cracks, tears, or excessive wear, it’s best to replace it. Damaged flashing won’t provide a watertight seal and could lead to leaks.

Material… Metal flashings like galvanized steel or aluminum are generally more reusable than plastic flashings which tend to become brittle over time.

Removal Process… If the removal process damages the flashing significantly (e.g., bends or tears), it might not be suitable for reuse.

Benefits of Reusing Flashing (if in good condition):

– Cost-effective: Reusing existing flashing can save you money on material costs for the new roof.

– Less Waste: Reduces construction waste by avoiding unnecessary disposal of old flashing.

Drawbacks of Reusing Flashing:

– Potential Leaks: Using damaged flashing can lead to leaks and future roof problems.

– Compatibility: New shingles might require different flashing sizes or types compared to the old ones.

– Hidden Damage: Flashing hidden under old shingles might have unseen damage that becomes apparent during removal.

When to Hire a Professional:

– If you’re unsure about the condition of your old flashing.

– If the flashing removal process seems complex or risky.

– If you’re unsure about the compatibility of the old flashing with your new roof materials.


While reusing old flashing can be a cost-effective option, it’s crucial to prioritize a watertight and long-lasting roof.  Consulting a qualified roofing contractor is highly recommended.  They can assess the condition of your old flashing, determine its suitability for reuse, and ensure proper installation for optimal roof performance.

When to Repair a Roof Flashing Leak

You shouldn’t wait to repair a roof flashing leak.  Even a small leak can lead to significant water damage over time, affecting your roof structure, ceilings, walls, and even mold growth.

Here’s why prompt action is important:

Why Fix Roof Flashing Leaks Quickly?

Progressive Damage… Water leaks don’t stay isolated. Left unrepaired, a flashing leak can cause progressive damage to the roof deck, underlying structures, and interior elements.

Mold Growth… Moisture promotes mold growth, which can lead to health problems and property damage.

Increased Repair Costs… The longer a leak goes unaddressed, the more extensive the damage becomes, potentially leading to more expensive repairs.

Roof System Integrity… Flashing plays a vital role in protecting your roof system from water intrusion. A compromised flashing can lead to further water infiltration and potential roof failure.

Signs of Roof Flashing Leaks

Visible Stains… Look for water stains on ceilings or walls, especially near chimneys, vents, or roof edges – common areas for flashing.

Mold Growth… Mold growth on ceilings or walls can indicate a leak originating from a flashing issue.

Missing or Damaged Shingles… Missing or damaged shingles around flashing points can expose the underlayment and increase the risk of leaks.

Rotting Wood… Rotting fascia boards, soffits, or rafters can be a sign of water damage caused by a flashing leak.

Taking Action:

Identify the Source… If you suspect a flashing leak, try to identify the source of the leak from inside your house (if possible).  Look for water stains or trails that might lead you to the general area of the leak.

Temporary Measures… While you wait for a professional repair, you can take temporary measures to minimize further water damage.  Place buckets or containers to catch dripping water and cover any exposed areas with a tarp (weather permitting).

Contact a Qualified Roofer… Don’t attempt to fix a roof flashing leak yourself, especially if it involves working at heights.  Contact a qualified roofing contractor as soon as possible.  They can assess the damage, determine the cause of the leak, and recommend the best course of action for repair.

Remember, Early detection and prompt action are key to preventing major damage from a roof flashing leak.  By prioritizing a professional repair, you can ensure a watertight roof and avoid costly consequences in the long run.

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