The roof area of a typical Canadian home may be as large as 1,700 square feet, or 244,800 square inches. A cubic inch of water flowing down it is equivalent to 0,0035 imperial gallons.
If an inch of rain falls on that roof in a storm, then the total cubic volume will be approximately 850 gallons. This is a mighty amount of water tumbling down a roof, and why every chimney needs step and kick flashing.
How Flashing Protects Roof To Wall Interfaces
That mass of water we referred to, usually tumbles down a roof surface easily, because the shingles, tiles, etc overlap their top and bottom edges in the right direction. However, that solution cannot work where the roof comes up against a wall.
Flashing refers to strips of thin waterproof material laid across those interface points, so the water flows over them smoothly. This helps prevent water leaks at chimneys, vent pipes, walls, windows and door openings, assuming annual inspections and maintenance.
Installing Step and Kick Flashing On Chimneys
Step Flashing on Chimney Sides
Step flashing, as the name suggests, steps down the side of a chimney, as it follows the slope of the roof. This diverts the water sideways, because it cannot find a way through the joint. That helps keep the moisture away from the roof covering, and considerably reduces the possibility of damp below.
Flashing comes in a variety of different materials, ranging from lead, aluminum, copper and other metals, to flexible flashing solutions. The latter must be applied on a scrupulously clean roof, and will probably need replacing every few years as adhesion weakens.
Kick Flashing at The Eavestrough Interface
More water damage may occur if a chimney protrudes beyond a perimeter wall, as we illustrate in our before-photo at the top of this article. This image shows how water has splashed down the wall over a long period, instead of flowing into the gutter (since removed).
We frequently find kick flashing missing at the lower edge of chimneys when we arrive at client sites. Now if they only had kick flashing in place to prevent the rainwater splashing their siding, then they might not have needed to ask Valiant Exteriors to solve a damp problem.
More Information
Draining An Upper Half-Hipped Roof
Draining Water From Shared Valleys
No Kick Flashing at Client Site (Valiant Exteriors)