What is roof flashing?
Sheet metal strips installed around roof penetrations and joints to direct water away and prevent leaks at vulnerable seams.
Roof flashing is sheet metal material installed at roof joints and penetrations to seal gaps and direct water away from the underlying structure. Water naturally seeks the lowest point and flows downward, so flashing overlaps shingles or standing seam panels in a way that sheds water safely off the roof rather than allowing it to pool or run underneath.
Common flashing types are identified by their location and function:
- Chimney flashing wraps around the base of the chimney where it meets the roof deck.
- Step flashing (or roof-to-wall flashing) seals where a wall or vertical surface intersects a sloped roof.
- Vent flashing fits around pipe penetrations and vent stacks.
- Valley flashing lines the channel where two roof planes meet.
- Skylight flashing forms a weathertight seal around skylights.
- Edge flashing runs along the perimeter of the roof at eaves and gables.
Flashing is typically made from galvanized steel, aluminum, or copper. Improper installation or deteriorated flashing is one of the leading causes of roof leaks in Ontario homes. When flashing fails due to rust, poor overlap, or missing sealant, water enters the attic and wall cavities, leading to rot, mold, and structural damage. A qualified roof repair contractor can inspect flashing condition, replace damaged sections, and ensure proper overlap and fastening during roof work.