Corroded metal roof flashings

Cause

Air-borne salt, dust or dirt accumulating under flashings

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

The paint finish has deteriorated, exposing steel 

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

Loss or breakdown of stone chip coating (pressed metal tile roofing flashing)

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

Loss of galvanising or zinc/aluminium alloy coating exposing the base metal 

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

Run-off from incompatible materials such as glass or plastic roofing

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

Run-off from cement-based mortar (tiled roofs)

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

Acidic run-off from uncoated cedar wall cladding

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

Debris or swarf (metal filings and chips) accumulated in valley gutters

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber 

Cause

Moisture being held within the lapped joints 

Repair

  • remove the affected flashing where practical; wash to remove salt, dust and dirt; sand or brush with a stiff bristle brush to remove corrosion; apply zinc-rich primer plus a metal primer to sanded/brushed areas, particularly where flashing is lapped; apply at least two coats of acrylic paint
  • if badly damaged, replace the flashing; ensure that the replacement flashing is compatible with the roofing
  • replace corroded galvanised steel valley gutters on tiled roofs with an inert material such as butyl rubber