Sometimes roofing terms can be downright mystifying to folks who aren't all that familiar with the roofing business. Flashing counts as one of those terms. To the uninitiated, the term may conjure up mental images of lightning or even a fast moving superhero, but what in the world does the term have to do with roofing? Although the term doesn't refer to a superhero in this context, flashing does serve a crucial salvific function for your roof by protecting it from leaks and water damage.
Every roof has areas that are particularly susceptible to leaks. Some of the most vulnerable areas are those spots where the roof decking comes up against obstacles, such as chimneys, dormers, skylights, pipes, vents, or other sections of roofing deck (forming a valley). These spots all have one thing in common: they create gaps in the decking where water can easily sneak in and wreak havoc on a home. Even if you have a great product like ice and water shield installed around those areas, there's still a chance that water could creep down into those vulnerable crevices. That's why you need flashing to give your roof additional protection.
Flashing is a protective barrier that is installed over vulnerable crevices to keep water from getting in. It can be made of many different materials, such as galvanized steel, lead, copper, aluminum, felt, rubber, or plastic. Depending on the type of roof you have, one material may work better than another, but the most dependable materials for flashing tend to be galvanized steel, copper, or aluminum because of their weather resistance and flexibility. Conversely, felt, rubber, and plastic are cheaper and often less durable options. It is vital for flashing to be made of a material that is both lasting and flexible because it has to be able to maintain its protective abilities as your roof expands and contracts with the changing seasons. Properly installed flashing will always keep your home leak free, no matter what the weather's like outside.
A good contractor knows there are various types of flashing for different objects. Chimneys, for example, require four unique types of flashing to be fully protected: continuous flashing, step flashing, saddle flashing, and cap flashing. Continuous flashing is designed at an obtuse angle to protect the lower joint where the chimney meets the roof. Similarly, step flashing is perpendicular and protects the crevices along the sides of the chimney, and saddle flashing is acute and protects the joint at the top. Cap flashing, on the other hand, is not formed at an angle but is instead mortared or caulked on top of the other types of flashing to ensure that water does not get in behind them. This process is the same for dormers and skylights, except that dormers don't usually require saddle flashing and skylights sometimes come with a pre-designed piece of uniform flashing to be used instead of the other types. Other than that, it's usually very similar.
The flashing process is less complex for other objects. For instance, pipes and vents only require a single piece of conical flashing with a hole cut out of the middle for complete protection. Likewise, valleys only need a single 2-3' wide piece of W-shaped flashing. And L-shaped drip edge flashing should always be installed along the eaves and rakes (edges) of a roof to keep water away from the decking and in the gutters where it belongs. Taken together, these various types of flashing comprise a waterproofing super team!
Although flashing is simple to install on your own, it is also dangerously easy to damage on accident and can be quite costly to repair if installed improperly. For this reason, it is always better to have your flashing installed by a licensed and experienced contractor. Not only will it save you the trouble of having to get up on your roof on your own, but it will also protect your home from costly leaks and water damage down the road.