Why do all roofs need corrugated Roof Flashing?

What is the Roof Flashing?

Roof flashing is a thin layer of metal sheeting used to direct water away from seams and joints where moisture could penetrate the roof and cause water damage. It’s placed underneath shingles and keeps water from damaging your roof.
 

What is the Purpose of Flashing on a Roof?

Roof flashing is required on your roof to keep water from getting underneath your shingles, with the help of underlayment. Flashing is critical to certain areas of your roof —  namely, the places where the roof surface meets a wall, valleys, protrusions such as vents and skylights, and the roof’s edges.

Types of Roof Flashing

Most flashing is made from metals like aluminum, copper or stainless or galvanized steel. Flashing can be used around windows, doors, chimneys, gutters — basically any exterior joint where water needs to run off.

Common types of roof flashing include:

Base Flashing & Step Flashing

Base flashing and step flashing are used where a vertical wall of the house intersects the surface of the roof deck. The two main types of walls are:

1.         Front walls (also called headwalls): Vertical walls behind a sloping roof deck

2.         Sidewalls: Vertical walls along the edge of a sloping roof deck

As wind blows and rain pours, you can imagine how water would be blown against the walls of this home. The water would run down the wall and right into the joint where it meets the roof deck below.

Thanks to base flashing at the joint, water is stopped before it gets between the wall and the shingles and is directed into the gutters. Roof flashing acts sort of like a gutter for your roof deck!

Some key points to remember:

Base flashing is the solution for front walls. It’s one length of flashing that is bent (along the length) to match the pitch of the roof. Base flashing is installed over underlayment, but under siding and shingles, so you may not be able to see it from the ground.
 

Step flashing should always be used where the roof deck meets a sidewall. Pieces of step flashing are bent at an angle relative to the roof pitch and installed along the full length of the sidewall where it joins the roof deck. The flashing should be partially exposed along the wall. Since you can see step flashing, some homeowners choose a more expensive flashing material like copper to achieve a certain aesthetic.

Valley Flashing

Valleys are the places where two roof decks slope toward one another, creating a low line that looks like a valley between two mountains.

Water flows into the valleys on your roof the same way rivers wind through mountain valleys. Valleys, as you’d imagine, are a prime target for water penetration.

So what to do? Some shingles can be woven to provide extra layers of protection to the roof valleys. However, many dimensional shingles are simply too thick and inflexible to be woven.

The solution: valley flashing.

Metal valley flashing is installed over the underlayment, but under the edges of the shingles. In this “open valley” style, the shingles over each section of roof do not touch. They are installed to overlap and form a gap that exposes the valley flashing.
 

This allows water to run off the edges of each roof, into the valley flashing, and down to the gutters.

Valley flashing is visible from the ground. Some homeowners choose a unique color of valley flashing to add a striking contrast to the color of their shingles.

What materials should be used for Roof flashing?

As a homeowner, you’re probably familiar with the shingles on your roof, or whichever other roof type keeps your home dry and safe. Amidst these popular materials, however, is the less popular but equally important roof flashing material. Flashing is a necessary component of your roofing system and you can usually find it in the areas of your roof where two surfaces meet, such as between the roofing and siding or skylights. Its function is to keep these more vulnerable spots of your roof safe from the weather and put off the need for roof repair or replacement any time soon.

If you have a metal roof, then galvanized steel would be the natural choice since it is also the same material used for the roofing system. This material comes with a zinc coating to make the flashing less susceptible to corrosion and withstand long-term exposure to moisture.