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Exterior Remodel Best Wall Assembly

user-7558824 | Posted in Energy Efficiency and Durability on

I am looking at an exterior remodel in which we are removing 4″ + thick Log Siding. The architect is calling to have the siding removed and to add ripped 2x furring to the exterior with sheathing to attain an additional thickness of 4 3/16″. That exact dimension is important because of dimensions of the house is based on a spiritual. I spoke with the homeowner about this being a good opportunity to add exterior insulation. I am looking for input of the wall assembly that would be the best fit. 

My thoughts were as follows. Reinstall a house wrap on the original sheathing where the windows will remain installed with a nail fin. Add 1 layer of 2″ rigid foam, 1 layer 1″ rigid foam, 7/16″ Zip System and 3/4″ furring for Rain Screen.
I would use solid 2x furring around the doors and windows to allow for sheathing and trim fastening in these areas then use liquid flashing to flash the recessed windows and doors. 
I’ve attached the scanned drawing from the architect
Looking for other input on this system.

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Replies

  1. creativedestruction | | #1

    What is the thickness of the composite siding, and won't it bust your overall target dimension?

    Zip sheathing is unnecessary in this application when you put a WRB on the existing sheathing. 2x4 furring over the foam layers would work fine. Spacing of the furring is dependent on the siding specs.

    1. user-7558824 | | #2

      Thanks Jason

      My concern of having the WRB solely located at the existing sheathing is that I am unsure of how to get the detail perfect without removing the existing windows.
      Adding the housewrap there would really just be a belt and suspenders approach.

      Do you think it would be wise to leave it off entirely or do you agree?

      1. creativedestruction | | #3

        The foam can also serve as a decent secondary WRB.

        Yes, it's difficult to integrate any WRB properly when existing windows stay in place. In this scenario my preference would be for ample drainage rather than a layer of taped zip which will have less drying potential. Not saying it wouldn't work, just that IMO it's an unnecessary expense.

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