Head-Flashing for Michael Maines’s Fin Jamb Window Assembly
We’re building in central VA. Our assembly is: 2×6 with dense-pack cellulose>>1/2″CDX sheathing>>housewrap>>2″mineral wool>>1×4 strapping>>Hardie plank.
We set our flangeless tilt-and-turn windows in the middle of the wall (i.e. in plane with the sheathing. They are flashed into the Tyvek. Michael Maines’s article on windows in thick walls has been our touchstone for window placement. greenbuildingadvisor.com/article/windows-in-thick-walls. We used his “recessed windows with fin jambs” approach.
My questions is: With this kind of assembly what are the recommendations or best practices for head flashing? Chris Laumer-Giddens work (LG Squared) has made a lot of sense to me. I watched a video of his with a similar assembly https://www.youtube.com/watch?v=cfcrgIU6avY and I don’t see how he would be tying head flashing into his water control layer. I’d be grateful from any feedback from the community here.
Many Thanks,
Phil
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Replies
Phil, I'm glad you found my article helpful. We didn't show the head or sill details because each of them could be at least a full article on their own, and probably more than one, due to so many options.
The most important thing to consider is maintaining a continuous water control layer (WCL or WRB). Your Tyvek is the main component of that and any flashing that sees a significant amount of water should be sealed to it, preferably with a mechanically lapped connection. If the cladding is reasonably watertight--i.e., not open-joint cladding or vinyl siding--and I'm confident in the WRB, sometimes I just extend the window head flashing to the back of the siding. A small amount of water will get past it but if the WRB is done well it won't matter.
A better approach, and important with open-joint claddings, is to extend the head flashing to the WRB/WCL as well. This is easiest when you have solid bucks around the opening and poses an order-of-operations problem. I don't have a drawing ready to go that shows that detail but I'll share one that's similar. The WRB is at the sheathing and drains over the window.
(Disclaimer #1: for illustrative purposes only. #2: I don't want to discuss other details of this assembly. #3: I need to re-watch our BS + Beer Show with Alexandra and Steve Baczek, Armando Cobo and Barry Price--showing high-performance details legibly is harder than it looks, and it's not my strong suit.)
Thanks, Michael. This is really helpful. Based on your feedback I think we'll tie it back to the WRB. It does complicate our order of operations, but I think I'll feel more confident in the end result. Thanks again!
Phil