What flashings actually are
Flashings are the metal strips and detail pieces that seal joins on a roof. They sit anywhere two surfaces meet: two roof planes coming together, a wall meeting a roof, a chimney sticking up through tiles, a valley running down between gables. Each one has a single job, to direct water away from that join.
There are a lot of named flashings: apron flashings, valley flashings, ridge flashings, barge flashings, parapet cap flashings, soaker flashings, step flashings. They all do variations on the same job. When they fail, water gets in.
What "deterioration noted" actually means
It means the building inspector has visually observed wear, damage, or aging on one or more flashings. The exact thing they saw might be any of the following:
- Rust or surface corrosion, especially where the protective coating has worn through.
- Lifting or movement, where the flashing is no longer sitting tight against the surface it's supposed to seal.
- Cracking or splitting, often at folds or end stops.
- Failed sealant, where the silicone or sealant bead at the top edge has aged out and is cracking, shrinking, or pulling away.
- Missing or corroded fixings, where screws or clips holding the flashing have failed.
- Sagging or distortion, often from foot traffic or impact.
Real building report phrasings you may have seen:
"Deterioration / damage noted to flashing/s. Recommend repair to inhibit water intrusion and further damage."
"Incorrect flashing. Recommend this is assessed and replaced to prevent moisture penetration."
"Flashings in serviceable condition. Recommend resealing all flashings and through-the-roof vents as part of routine maintenance."
The first two are findings. The third is the standard maintenance note that appears on almost every building report regardless of condition.
"Incorrect flashing" is different
If your report says incorrect flashing rather than just deterioration, that's a slightly bigger flag. It usually means:
- The flashing installed isn't the right type for that detail.
- It's the wrong size or shape.
- Critical features are missing (e.g. no upstand, no end stop, no soaker).
- It's been installed in the wrong direction (water running into the building rather than away from it).
"Incorrect flashing" is often a signal that the roof has been worked on by someone without roofing-specific knowledge, and is worth looking at more carefully.
Why flashings matter so much
The cladding (the tiles or metal sheets) covers the big flat areas. But the joins, where two surfaces meet, are where almost all roof leaks happen. Flashings are doing the actual waterproofing work at those joins. When a flashing fails, water finds its way in immediately. Many older Wellington roof leaks come down to the flashings, not the cladding.
How serious is it?
Flashing deterioration sits on a wide scale. To give you a sense:
Minor (likely just maintenance)
- Aged sealant at the top edge of an otherwise sound flashing.
- Light surface rust on galvanised flashings, not through to the metal.
- One or two missing fixings on an otherwise intact run.
Moderate (worth addressing within a year or two)
- Multiple flashings with deteriorated sealant.
- Lifted edges on apron or pan flashings.
- Rust through the coating in localised areas.
Bigger flag (worth a closer look before settlement)
- "Incorrect flashing" on critical details like valleys, aprons, or parapet caps.
- Widespread flashing rust suggesting the whole set is end-of-life.
- Flashing deterioration combined with visible interior staining or water marks.
- Flashings on a flat roof or balcony where water sits, not just runs past.
What to do if your building report flagged flashings
- Read the report carefully. Note which flashings, which finding, and where on the roof.
- Don't panic. Most flashing issues are repairable. The question is scope and cost.
- Get a roofing-focused assessment. An assessor with roofing knowledge can tell you whether you're looking at minor maintenance or a bigger issue, and a drone lets them see flashings on roof areas the building inspector couldn't reach.
- Use the assessment to decide. The written letter gives you a basis to negotiate, request work, or move forward.
Common questions
How much does it cost to fix deteriorated flashings?
It varies widely. Resealing a few sound flashings might be a couple of hundred dollars total. Replacing apron or valley flashings can run from several hundred to a few thousand depending on length and complexity. Major flashing failure tied to broader roof system issues can be significantly more. A proper assessment lets any repair quote be for the right scope.
Is deteriorated flashing a deal-breaker when buying a house?
Usually no, but it depends on the extent. A few aged sealant joints are minor. Widespread rust on multiple flashings, or "incorrect flashing" on critical details, could indicate a bigger issue and is worth understanding before you commit.
Can flashings be repaired or do they always need to be replaced?
Many flashings can be repaired or refurbished, including resealing top edges, refixing where loose, treating localised rust, and adjusting where they have lifted. Where the flashing itself is end-of-life (extensive rust through the coating) or incorrect for the detail, replacement is the right move.
Should I get a roofer to quote or get an assessment first?
An assessment first. An assessment gives you a written record of the actual scope first, so any repair quote you get afterwards is priced against the right work. Once you have the assessment, you can take it to any roofer for a quote on the right scope.