What is Flashing and Why is it Essential for your Roof?

What is Roof Flashing, Why is it Important, and How is it Properly Installed?

What is Roof Flashing?

Roof flashing refers to thin pieces of material, often metal, used to prevent water from seeping into a structure from joints or penetrations in the roof. These materials are installed where the roof plane meets a vertical surface like a chimney, wall, or dormer, or where the roof's slope changes, such as at valleys or around skylights.

Why is Roof Flashing Important?

The primary function of flashing is to direct water away from vulnerable areas to ensure that water doesn't infiltrate the roof's structure - leading to rot, mold, and structural damage. Without flashing, water can easily find its way into the building through gaps where different materials meet or where the roof's integrity is compromised by penetrations like vents or chimneys.

Properly installed flashing can extend the life of a roof by protecting underlying materials from water damage. This is crucial in areas with heavy rainfall or snow. Flashing can also enhance the aesthetic look of a roof, providing a finished appearance to transitions and intersections.

What are the types of roof flashing?

Roof flashing comes in various forms, each designed for specific areas or purposes on a roof. Here are the main types of roof flashing:

1. Step Flashing is installed where a roof meets a vertical wall, such as around chimneys or dormers. It consists of individual pieces that "step" up the wall, each piece overlapping the shingle below it to create a watertight seal.

2. Continuous, or Apron, Flashing is often used along the edge of a roof where it meets a vertical wall, especially in areas where step flashing might not be practical due to the wall's height or the roof's pitch. This is a long, single piece of flashing that runs continuously along a seam in the roofing materials.

3. Valley Flashing is installed in the valleys of a roof where two slopes meet to direct water flow down the roofline. Valley flashing can be "open" where the flashing is exposed, or "closed" where the shingles cover the flashing. Closed flashing provides a more aesthetic look, but potentially offers less durability.

4. Vent Pipe Flashing is used around pipes that penetrate the roof, like plumbing vents. This type of flashing is often circular or square, designed to fit snugly around a pipe with a base that sits under the shingles and a cap that overlaps them.

5. Chimney Flashing is specifically designed for chimneys, where the roof meets the chimney. This typically includes both a base and counter flashing. The base flashing is installed under the shingles, and the counter flashing (or cap flashing) is attached to the chimney to overlap the base flashing.

6. Drip Edge Flashing is employed along the eaves and rakes of a roof to prevent water from running back under the shingles.  The drip edge flashing forms a small lip that directs water away from the fascia and into the gutters.

7. Kickout flashing is used at the intersection of a roof and a wall where water could flow back into the wall. The kickout directs water away from the wall, and is often used in conjunction with step flashing.

8. Skylight Flashing is used around skylights to prevent leaks. This type of flashing can be custom or pre-fabricated, and is designed to integrate seamlessly with the skylight frame and the surrounding roof.

9. Cricket flashing is a small, peaked structure that helps water flow around the chimney rather than pooling behind it. It is often used around chimneys or other vertical protrusions to divert water flow.

10. Sill Pan Flashing is employed below windows or doors that penetrate the roofline. It forms a barrier to prevent water from entering the building through these penetrations.

11. Base Flashing is used underneath other types of flashing or roofing materials to provide a foundation for other flashing components and is often hidden under shingles or other roofing materials.

How is Roof Flashing Installed or Repaired Properly?

Each type of flashing has a unique installation method, but all serve the common goal of preventing water infiltration and ensuring the longevity and integrity of the roof. Proper selection and installation of these flashing types are crucial for effective water management on any roof.

Considerations for Installing New Flashing

• Common materials for flashing include aluminum, copper, galvanized steel, or lead. The choice depends on the roof's material, local climate, and aesthetic preferences. For instance, copper might be chosen for its longevity and aesthetic appeal, while aluminum is often preferred for its cost-effectiveness.

• Preparation is key! Before installation, the area must be clean and dry. Any old flashing or damaged roofing materials should be removed.

• The Base Flashing is the part of the flashing that is embedded under the roofing material. It is usually installed first to make sure that it is properly tucked under the shingles or tiles to prevent water from getting behind it.

• Cap Flashing overlaps the base flashing and is visible on your roofline. It's often secured to a vertical surface (like a chimney) with sealant or nails, to ensure that water flows over it and not underneath.

• High-quality sealants or roofing cement are used at critical points to prevent water penetration. These should be compatible with the flashing material to avoid corrosion and ensure a long life.

• Be sure to check that there is sufficient overlap in the flashing to prevent water from sneaking in at the seams. Typically, overlaps should be at least 4 inches.

Considerations for Flashing Repairs

• Regularly inspect your roof for signs of flashing failure, like rust, cracks, or gaps where it meets other surfaces.

• Remove debris and clean the area around the flashing. Sometimes, simple cleaning can restore functionality.

• If there are minor leaks, applying a fresh layer of sealant might suffice. However, ensure the surface is dry before applying.

• If the flashing is severely damaged or corroded, it should be replaced immediately. This involves first removing the old flashing carefully to avoid further damage. Then, new flashing will be installed as described above.

• For complex repairs - or if you're not comfortable with heights or roofing work - hiring a professional is advisable. They can ensure the job is done correctly, reducing the risk of future leaks.