How to treat rusty spots in metal angle flashing?

[sirblew]

Hi,

I have a roof leak caused by holes in the angle flashing which sits in the crevice where the window dormer protrudes from the main roof. The roof is a cape cod style tiled roof, and the steep angle makes it very hard to access from the outside. So I want to repair the rust holes from the inside of the ceiling.

If I use flashing tape the adhesive side will be facing outside, which is not how its intended to be used. Will the water and elements end up detaching the tape in the long term?

Is silicon a better choice, or will that create issues with water flow? I won't be able to smooth it from the outside, so can imagine it bulging outwards and preventing water from flowing downwards properly.

TIA!

[MitchellMc]

Hi @sirblew,

To start, any repairs to water leaks are best done on the outside. Any fix from the inside is considered a bandaid solution, so it's hard to determine how effective it will be. If you can monitor the situation, I'd suggest that a Butyl-based flashing tape would do a reasonable job from the inside if the surface was prepared well and stuck down adequately. If the tape is only there to prevent shedding water from entering the holes, it should hold. However, if water pools over those holes, it will likely make its way back under the tape after some time.

Just remember that although you might be able to stem the leak, you're not resolving the issue, which is a flashing that needs to be replaced. After your emergency fix, I'd encourage you to enlist the services of a professional to perform a more permanent repair.

Please let me know if you have any questions.

Mitchell

[sirblew]

Thanks. I discovered more rust holes and also realised that the main hole I thought I'd patched can't be fully covered from below. So I ended up removing roof tiles from the inside of the roof to enable access to patch it from the outside. I was able to clear the debris and patch the flashing from the outside with Byute flashing tape. We haven't had much rain since I did that but I'm fairly confident the problem is solved now.

[EricL]

Hi @sirblew 

It's good to hear you've patched up the damage to your flashing. My best advice is to observe and see if the repairs will hold up in the next time it rains.

If you need further assistance, please let us know.

Eric