Roof flashing is the formed metal or other material that carries water past the points where roofing cannot simply continue. Roof flashing repair corrects those details when they stop doing that job, and flashing installation puts them in place where they are needed.
This service rests on one principle: flashing protects the places where a roof changes direction, meets another surface or has an opening. It is never an isolated piece of metal: how well it works depends on how it connects to the roofing and the surface around it.
How Flashing Keeps Water Out
Flashing works as part of a layered arrangement. Each piece overlaps the one below it in the direction water flows, so water is handed from one surface to the next and carried past the joint. The order in which the pieces are laid matters as much as the pieces themselves.
Flashing reduces the risk at a vulnerable point; it does not make the joint permanently waterproof on its own.
Three Kinds of Places That Need Flashing
Where the roof changes direction: valleys where two slopes meet, transitions between roof sections. The flashing has to carry the water that concentrates at the junction.
Where the roof meets another surface: walls rising above the roof, chimneys. The flashing has to keep water from running into the joint between roof and wall.
Where the roof has an opening: vents, pipes and other penetrations; skylights. The flashing has to carry water around the opening instead of into it.
Not every house has every one of these, and the details at each vary with the roof. The details GoodVans Roofing handles include flashing at chimneys, valleys, vents, skylights and roof edges.
Repairing or Replacing Flashing
Flashing repair may be relevant when the flashing is serviceable, a contained part of the detail has failed, and the roofing around it is in reasonable condition.
Flashing replacement may be relevant when the flashing is too deteriorated or damaged for a contained correction, the joint needs to be rebuilt, or work on the surrounding roofing means it has to be renewed.
Flashing can be repaired on its own, without a full roof replacement, and complete flashing replacement is also available when repair would not make sense. The choice follows the condition of the flashing and what it connects to.
Flashing and the Surfaces Around It
Flashing only works in combination with the roofing it laps into and the surface it meets.
If the roof covering beside a chimney has deteriorated, or the wall above a roof junction is admitting water, new flashing on its own may not stop the leak.
That is why the condition of the whole joint matters: the flashing, the roofing around it and the adjoining surface. Problems within the chimney, siding or wall itself are outside the flashing and need to be identified as such rather than covered over.
Installing New Flashing
New flashing is needed where a detail is missing, was never properly formed, or is created by a change to the house, such as a new vent, an addition or a new roof section. Flashing is shaped and detailed to suit the specific roof interface. Installation may require the surrounding roofing to be lifted or reworked so the flashing integrates correctly with it.
Signs of a Flashing Problem
Flashing-related problems can show up as flashing that has lifted, shifted or come away from the surface it should follow; rust or corrosion on metal flashing; gaps opening between the flashing and the wall, chimney or roofing; deteriorated sealant or detailing around the flashing; damage after other work near the joint, such as siding or chimney repairs; or water appearing near a wall, chimney or valley.
These are signs worth checking, not proof. Water near a chimney can come from the flashing, the roofing beside it or the chimney itself. When it is not clear which part is contributing, Roof Inspections can help establish the condition before any flashing work is scoped.
- Lifted or shifted flashing
- Rust or corrosion
- Gaps at the joint
- Worn sealant
Flashing During a Re-Roof or Around a Skylight
A full roof replacement is a natural point to reconsider how each flashing detail meets the new roofing; that project is covered under Residential Roof Installation & Replacement. A skylight also has flashing around its opening, but the skylight unit and its installation belong to Skylight Install & Replacement.
Where Flashing Is Not the Answer
Roof Inspections fits when you cannot tell whether a flashed joint is involved at all; Residential Roof Repair & Maintenance when the damage is on an open slope rather than at a joint; Skylight Install & Replacement when the skylight unit is failing, rather than the flashing around it; and Gutter & Vent Installation when water is overflowing at the eaves, or the concern is ventilation rather than a flashed joint.
For how all six residential services fit together, see Residential Roofing.
Roof Flashing Repair Across Metro Vancouver
Flashing repair and installation are part of GoodVans Roofing's residential service in selected Fraser Valley locations as well as throughout Metro Vancouver.
Roof Flashing FAQs
Can chimney flashing cause a leak?
Yes, it can be one cause. Chimney flashing that has lifted, corroded or separated from the masonry can let water into the joint. Water near a chimney can also come from the roofing beside it or from the chimney itself, so the source needs to be established before repair.
What is the difference between flashing repair and roof repair?
Flashing repair deals with a joint: the detail where the roof meets a wall, chimney, valley or opening. Roof repair deals with the roofing itself, such as damaged or missing roofing on an open slope. The two can overlap where the roofing beside a joint is also affected.
Does a new vent or addition need new flashing?
A new roof penetration or a new roof-to-wall junction needs appropriate flashing or equivalent water-shedding detailing. How that detail is formed depends on the roof and the new interface, and the surrounding roofing may need to be reworked as part of the installation.
How can I tell whether the problem is the flashing or the wall?
Not reliably from appearance alone. The flashing, the wall above it and the roofing below can produce similar signs. Looking at the whole joint helps determine which part is contributing, because work on only one component may not resolve the water entry.
Concerned about a joint on your roof?
An assessment looks at the flashing, the roofing it laps into and the surface around it before a repair or replacement is chosen.
