# Q about flashing roof cement



## Pete271 (Jun 13, 2016)

Hi,
I used karnack #19 flashing cement on a flat roof. I forgot to clean the area with a brush or broom. I just added flashing cement, placed a mesh on it, and added more cement over it. 

It rained heavily 12 hours afterward, according to karnack site, the flashing cement needs 24 hours to skin over.

My question is do i need to redo it? Did the rain washed away the cement?


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## Pete271 (Jun 13, 2016)

I forgot to add the flat roof is bitumen firestone ap160 and is 2 years old


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## roofermann (Jul 7, 2012)

Needs redone regardless of rain, due to lack of prep work.


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