# Karnak 19 Ultra or karna-flex or ? for sealing a leak?



## michaelblack1001 (11 mo ago)

We have a commercial retail property. The roof is relatively flat, but double sloped from front back about 40 feet and from rear towards the front about 80 feet. Back in the day around 1960, some genius decided to put one of the two HVAC near the drainage valley with one downspout on each side. of that valley It doesn't puddle around the duct but greater amounts of water pass by it vs the other duct.

It's winter but we had a recent warm day (50+ F) in Chicago and it rained fairly heavy and long and there is a leak near the duct. I torched another layer of modified bitumen (with granules) around the entire duct, but it is still leaking. I checked the seams carefully and for any cracks or pinholes, but I cannot see exactly where it is entering from above. I was able to crawl underneath it over an old very heavy duty plaster and lathe drop ceiling. The leak is about 8-12" from one of the outer edges. I went over it with a torch but it is still leaking and driving me nuts!

I am not a fan of most roof cements with a low proportion of asphalts in them. I am looking for something that will last long term, like at least 10 years. I know many cheap roof cements will dry out and crack in the short term. But, it appears that Karnak 19 Ultra has a much higher percentage of asphalt solids as well rubber elements and chemicals that push water away. And, it can be applied supposedly under water as shown in videos. They also have a more expensive product- Karna-Flex that looks to be an acrylic/rubber hybrid sealant. I would start with the seams and use the reinforcing mesh and another coat after brushing and cleaning everything of course. I also plan to go around the duct where the membrane is terminated. 

Would it be better to brush Karna-Flex not just over the seams but over the entire area around the duct over the face of the membrane and a little beyond? Or just use the 19 Ultra on the seams? Or do something else?

Does anyone have any experience with either or both of the Karnak products that you can share with me? Is there a better sealant to use in this case? Silicone? Acrylic?

Thanks for any opinions, info and help,

Mike


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## michaelblack1001 (11 mo ago)

I had to make a decision and no one had Karak 19 Ultra or at least not in stock because of Covid and shipping container backup. I then looked at Lucas products that appear to be more widely available in Chicago. Their Elite 776 cement is very similar to Karnak 19 Ultra, and it seemed no one had that in stock either, but I just finally found one supplier that does, and I will be picking some up tomorrow.


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