GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Rainscreen around garage door opening and door opening

thomaskansas | Posted in General Questions on

I’ve seen many articles and videos showing rainscreen details on walls and around window openings. How does one treat door openings like garage doors?

The best I can figure the ‘casing’ trim needs to be flashed all the way back to the wall with the ‘jamb’ trim meeting the casing trim and drainage and ventilation accomplished between the casing trim and siding above
The casing trim need only be flashed back to the backside of the siding above and the jamb trim left shy of the casing trim so that drainage and ventilation can be accomplished between those two trims instead.

How do people approach this? Thank you.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. Expert Member
    Michael Maines | | #1

    Like most building science questions, the answer is, "it depends." What is your rain screen material, what is your WRB, what is your cladding and casing, etc..

    1. thomaskansas | | #2

      Thanks for the reply Michael, I should have known that was the answer!
      I'm working on the garage openings today. There I have Kimberly Clark Block-It drainage wrap, 3/4" CDX furring strips, and will be using 1-by (3/4") SmartSide trim for the jamb and casing trims with 3/8" SmartSide T1-11 siding.
      On the house I have GP Forcefield WRB.

  2. thomaskansas | | #3

    For future readers I ended up doing the first of the two options I presented.

    Jamb trim went on first, then casing trim with no gap left between the two (although a 1/4" reveal). Then little furring strips behind where the casing goes to space it off the wall but no taller than the casing. Z flashing over the head casing with the upper leg taped back to the housewrap. Furring strips continuing up to the top of the wall above the z flashing. Siding like normal on top of the furring strips.

    If I were doing this again I would have cut the housewrap and taped the upper leg of the z flashing to the sheathing and flapped the housewrap back over it. In my haste I hadn't considered it. Also 5/4" instead of 1-by trim for casing would have better matched the look of the picture framed window trims done with 1-bys.

    I think there is nothing wrong with either solution I presented but this one hides the rainscreen gap and makes it appear like a normal opening.

    1. midwestdiy | | #4

      I’m facing the same challenge. In your final decision you mentioned you did jamb, then casing with no gap to jamb, then furring strips behind your casing; that’s where you lost me. Are you saying your casing in directly on top of your sheathing then a second run or casing spaced off the wall with furring strips?

      I’m struggling to follow how you did your casing.

      1. thomaskansas | | #5

        I hung the casing trim on furring strips just like the siding. The only difference is I interrupted the furring strips where the head flashing needs to go all the way back to the sheathing. Hammer and Hand has a really good set of pictures.

        My comment about the 5/4 vs 1-by is because at my garage door I butted the siding up to the trim and caulked it. One the house I installed window trim on top of the siding. In both locations I used 1-by material but if I had used 5/4 on the garage casing it would have protruded off the wall more similarly to the window trim.

        Let me know if that isn't clear.

  3. midwestdiy | | #6

    Thank you that helps!

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |