Window flashing detail with rainscreen, end dam and hardie panel
Installing windows this week in BC, Canada on my owner build. I have a few questions about best practice and how to execute.
1. End dam and trim?
My plans call for a window head flashing with 22mm end dams, this will attach to sheathing and be lapped by my WRB, rain screen and trim.
Question is, am I to stand the head trim piece off the top of the window by the 22mm end dam or notch out the trim piece so that the end dams bed into the trim and it is only stood off by the required 1/4″? I’ve seen it notched on some houses in the area but think it is hard to make it look good. Not sure if having a 1″ gap would look better though?
2. Hardie panel install
Looking at the Canadian instructions it says its ok to either butt the panels into the trim or install trim over the panels.
I was planning to install over top because the battens would then project the same as the trim. But now I am wondering about how to flash the top of the trim in this case?
What is better practice?
a. butt panels to trim, furring out the trim to match the battens, and head flash both the top of window, taped to sheathing and lapped by WRB, AND top of trim, nailed to the battens.
b. install trim over panel and only flash at the top of window, caulk top of trim. Not sure if this even meets code here..
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Replies
Jason,
1. Notch the head trim to sit down onto the end dams. If you don't you will have a greater chance of getting wind blown rain moving up through the gap into the cavity. I leave a 1/8" gap which means I don't have to protect the cavities above the window with insect screen.
2. I prefer to place the trim on top of the panels. This is the one place where I caulk horizontal joints - I run a bead on top of the trim before installing the battens. If you place the trim in the same plane as the panels, or fur it out, you should move the head flashing from directly above the window to the joint between the trim and panels.
Here is a job I did with similar cladding and trim