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Detailing Intersection of Roof Overhang and Wall

deerefan | Posted in General Questions on

Hi,

I have attached a photo which demonstrates my question.

There is an intersection between a wall and a roof overhang in the home I am building. The wall will receive 3″ of external insulation. Should the insulation run between the sheathing covering the overhang or should the sheathing be attached against a wall to allow the 2 weather barriers to be continuous? I appreciate the input.

Marcin

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Replies

  1. Expert Member
    Michael Maines | | #1

    Marcin, your photo did not attach, but I think I understand your question. The answer depends on your other construction details. Is the roof vented or unvented? What is your climate zone (including A vs B, or wet vs dry).

  2. Jason S. | | #2

    The type of continuous insulation and whether or not it can be detailed as the WRB also matters. The kickout flashing ultimately needs to extend up and behind the WRB to effectively keep water out of the wall. Water management should drive the detail more so than thermal control.

    https://www.buildingscience.com/documents/insights/bsi-056-leiningen-versus-the-ants-redux

  3. deerefan | | #3

    The walls and roof will have a Cascadia clip system with 3" rockwool cavity rock insulation on the outside. Delta Vent SA on the wall and Carlisle Wipp 300HT on the roof as the WRB. The roof has a 1:12 slope so it is unvented. I did not consider kick-out flashing.

  4. Expert Member
    Michael Maines | | #4

    Marcin, I would prioritize making your assembly watertight, which means a continuous WRB.

  5. deerefan | | #5

    Should the flashing be placed at the roof-wall intersection between the primary WRB (placed on the roof-wall sheathing) or the secondary WRB covering the Rockwool insulation? Is there a preferred type of flashing? (shape, material). Thank you.

    1. Jason S. | | #6

      I assume roofing will be installed before exterior insulation and the second WRB? Your sequencing will drive the detail.

      https://hammerandhand.com/best-practices/manual/6-roofs/6-1-kick-flashing/

      1. deerefan | | #7

        Thank you for the reference. I will be using Carlisle WIP 300 HT as the primary roof WRB. Based on this, I plan on placing this 8" up the side of the wall at the overhang. I may plan on adding another small piece of delta Vent in that area to prevent a reverse lap.

        I am confused about the drip ledge. Should the WIP 300 be installed along the edge (with a small lap onto fascia), then a drip ledge and then WIP 300 all the way up the rest of the roof? What is the difference between "peel and stick" and roofing felt in Hand and Hammer diagrams? Thank you.

        I forgot to add, my fascia is essentially a sub fascia designed for equalizing the eave overhangs and soffit nailing. The roof will be metal and so the real fascia will be a metal piece that will cover this sub fascia. Do I still need the drip ledge in the diagrams?

        1. Jason S. | | #8

          Lots of ways to skin the cat, as they say. The weather lap principle is constant.

          Is the delta vent sa adhered? if not, you could just cut it and tuck the roof membrane up and underneath. The wip 300 may or may not bond to it..

          Yes to the wip 300 on the edge down a bit on fascia, then drip edge/gutter apron, then wip up the roof. Felt is just a more permeable cheaper roof underlayment, where 'peel and stick' is equivalent to the WIP.

          I would think the drip flash or gutter apron makes sense to tuck the metal fascia 'cladding' underneath but it depends on the metal profiles.

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