Replies

1. Expert Member
   MALCOLM TAYLOR | May 25, 2023 12:25pm | #1

   arnoldk,

   You have a couple of choices.

   - You can install the roofing and flashing much as you would if the house had no exterior insulation, then add the Comfortboard, strapping and siding. The WRB can be either behind or in front of the Comfortboard. If the WRB is behind, then all flashings have to go hack to the sheathing, if in front, the head-flashings at windows and doors can be installed on the Comfortboard.

   - You can install the exterior insulation before the roofing. All flashings will be run on the surface of the Comfortboard, and the WRB will be installed before the strapping.

   You can't run the flashing on the outside of the strapping because that gap is also a drainage plane, so water could get in behind.

1. 
   arnoldk | May 25, 2023 01:15pm | #2

   Hi Malcolm,

   My WRB was installed on top of the 1/2" plywood sheathing followed by the Comfortboard and the strapping on top.
   In my case, the sunroom was built in-front of the Comfortboard as per the stamped construction drawing to keep the continuous thermal brake around the house. This means I have about three inches from the WRB to the exterior siding.

   Since I cannot find any step flashing that will extend that far out from the sheathing to the edge of the roof shingles which leads me to believe I will need to use an Ice & Water membrane from the sheathing to the roof sheath?

   Let me if I am on the right path or if I am missing something.

   Thank you,
   Arnold

1. Expert Member
   MALCOLM TAYLOR | May 25, 2023 01:25pm | #3

   Arnold,

   Unfortunately, a membrane won't help.

   If the WRB, exterior insulation, and strapping are already installed, your choices are really limited. The step-flashing needs to go on the Comfortboard, and it needs to be protected by a second WRB, which laps the vertical leg, and extends up the wall to the roof. Otherwise any water that gets through your siding will get behind the flashing. That second WRB should extend down the walls of the existing house where it meets the sunroom several feet wide. Unfortunately that means removing the strapping to install it.

1. 
   arnoldk | May 25, 2023 01:44pm | #4

   Would the second WRB only be required for the width of the sunroom?

   Thanks,
   Arnold

1. Expert Member
   MALCOLM TAYLOR | May 25, 2023 02:11pm | #5

   Yes. Its purpose is just to keep water from getting behind the step-flashing. So just over the new roof.

   Exterior insulation is pretty straightforward, except for dormers, additions, and ledgers. Unfortunately you've got one of those three.

2. 
   arnoldk | May 25, 2023 02:54pm | #6

   I personally would not do exterior insulation again. It adds way more variable that required additional attention to details compare to a double stud walls, at least in my opinion and experience.

   Arnold

1. Expert Member
   MALCOLM TAYLOR | May 25, 2023 03:29pm | #7

   arnoldk,

   Interesting perspective to hear. I've only done simple, small structures with 2" foam. It wasn't too bad, but I didn't enjoy the added complications either.