question about waterproofing

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xu teng

February 10, 2022 03:38

can someone explain to me why counterflashing is used to keep water from penetrating an expansion joint at the intersection of a roof and wall? why not base flashing. 

i think the first lay is base flashing and the counterflashing is laid on top of base flashing. so base flashing is used to keep water out. 

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  Michael Ermann February 11, 2022 10:42

  The counterflashing can be relatively easy to remove when the roof membrane requires replacement

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  xu teng February 20, 2022 02:56

  thank you for your help. but i am still a little confused, why easy for removing makes counterflashing become determining factor to use over base flashing. 

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  Rebekka O'Melia March 02, 2022 15:59

  The counterflashing is used at the top of (vertical) membrane flashing.  If it weren't, the weight of it (it's 30" or more tall!) would tend to pull it down.

  See this website:  https://www.professionalroofing.net/Articles/Manual-Elements--02-01-2006/793

  and pic.

  Hope this helps!

  Rebekka O'Melia, Registered Architect, NCARB, B. Arch, M. Ed, Step UP,  Step UP ARE 5.0 Courses

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