How to seal holes in rusty galvanised roofing?

[RipVanCutter]

Hi Everyone!

Just wondering if anyone has any tips for this problem. I have a garage with ridge and valley type galvanised roofing. It is quite old and has served well, but at one end where there is a short retaining wall, vegetation has been collecting. As a result, full thickness rust holes have developed, which allows water to leak through underneath. Since the holes are near a corner, it is not just a simple matter of patching with a piece of sheet galvo, like if it were in mid span. Does anyone know of any suitable sealing solution for this kind of problem? Many thanks in advance!

[EricL]

Hello @RipVanCutter

Thank you for sharing your question about how to seal holes in rusty galvanised roofing. To give our members a better idea of the damage on your roofing, would it be possible for you to post a picture of it? We can then assess its location and condition. Our members can then make recommendations on how to proceed.

In order to slow down the oxidation of the galvanised roof, I suggest using White Knight 0.5L Rust Guard Rust Converter or similar in combination with White Knight Rust Guard 400g Cold Gal Spray Paint. I recommend removing all the loose rusty bits of the roof before treating it with the rust converter.

I often suggest using Consolidated Alloys 75mm x 3m Weatherproof Byute Flash Flashing Tape. It is ideal for repairs to roofing, gutters, downpipe and water tanks. 

We look forward to seeing the photos.

Eric

[RipVanCutter]

Hello Eric!

Thank you so much for your warm and helpful reply.

Here are some photos I took of the area yesterday. I washed away all the dirt, vegetation matter and possum poo to try and show exactly what it looks like.

If you look closely, you will be able to see that there are full thickness perforations through the rust. Hopefully this will help refine suggestions for a repair process.

Cheers,

Greg

[EricL]

Hello @RipVanCutter

Thank you very much for posting the photos of your roof. It seems that the vegetation and debris from animal waste have effectively damaged your galvanized roof. If you are not prepared to fully repair the damage at this time, I suggest going with my initial recommendation. But before you apply any of the repairs the roof must be totally dry. 

I also recommend changing the size of the tape to the Consolidated Alloys 100mm x 10m Weatherproof Byute Flash Flashing Tape. Using the larger product, you'll be able to cover more area with less tape. Please note that it is vital that the surface of the roof must be dust free as much as possible before you apply the tape. It's important to go past the rusted areas so that the tape will have a solid foothold on the undamaged section of the roof.

In order to accelerate the bonding process of the flash tape, I propose using a heat gun once the tape has been applied. The tape is not a permanent repair option and I suggest considering replacing the damaged portions of your galvanized roof.

If you have any other questions we can help with, please let us know.

Eric

[RipVanCutter]

Again, Eric, thank you so much for your help. I thought I would share what I ended up doing so that it might help some other people with a similar problem.

First of all, I cleaned the area as best I could, and removed all the loose material and loose rust. When it was dry, I treated the area with a liberal application of Ranex rust converter. I allowed this to dry overnight and waited until it was bone dry to the touch. I then used Crommellin Exterior waterproof membrane over all the treated areas. I used their bond breaker tape in the corners (the pre-formed internal corners) and flat tape over the full thickness holes. Two coats did the trick very well. That stuff is great: very "goopy" and sticks very well (though some advice to all: wear disposable gloves!). Once dry, I put some of the Consolidated alloys byute tape over the most vulnerable areas to really seal it. The membrane provides an excellent substrate for the tape: it adheres really well to the dry membrane. Here are some photos of what it looks like after the membrane dried. Thanks again, and hope it might help others!

[MitchellMc]

That looks like a great solution, @RipVanCutter! I love the idea of painting the brushable waterproofer over the entire surface.

Many thanks for sharing your results with us, as it really helps paint the whole picture for members with a similar issue that come across this discussion.

Mitchell

[EricL]

Hi @RipVanCutter 

Thank you so much for posting your excellent handy work. I reckon that repair job should last you another 10 years before you need to add more byute tape! I suggest keeping an eye on the leaves and debris that keep accumulating at the end of the gutter, they tend to hold moisture and contribute to the acceleration of rust development on your roof. I'm sure our members will find the information you shared very useful.

Again, thank you for sharing your excellent repair project.

Eric

[RipVanCutter]

Thanks very much for the comments Eric and Mitchell! Hopefully it will do the job for a while...the best part is I can now make a ceiling for the toilet that is underneath where the holes were (and where the water was getting in!)