Window flashing details on renovation with multiple siding layers
I am well into the gut and rebuild of the second storey in my 1.5 storey home. It’s about time to order windows, so I removed the old wooden frame single panes with aluminum storm window to get the rough opening measurements.
It appears as though my home had 3/4″ wood siding, on top of which aluminum siding was added at some point. I have shiplap plank sheathing with felt as the WRB.
Because the old windows were site build, there was some material that needed to be cut away via sawz-all to fully expose the rough opening framing. I would prefer to leave the siding, with j-channel, and drip cap in place, but I’m having difficulty coming up with a flashing strategy. I planned to use flexible flashing tape in combination with a slope sill pan, however, with all the extra “material” around my window frame I’m not sure it’s fully possible with out cutting back a lot of the material to expose a few inches of felt.
As you’ll notice in the photo’s, the drip cap was never integrated with the WRB. It would be simple enough to slide a piece of Z flashing up behind the felt, however taping it would be a problem. Same goes for a sill pan, as is i could slide one between the felt and the original wood siding, but fully sealing it would be difficult.
Any tips?
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Replies
This appears to be the wall assembly from best I can tell.
You can run the peel and stick to the old WRB, but I would make the pan flashing dump out past the existing AL siding. Check that your peel and stick is compatible with felt.
For the window sides, if you can remove the J trim and get the metal flashing behind it and re-install, it would be the cleanest. If hard to get out, you can get the side flashing bent so it hooks over the edge of the existing J channel.
For the head flashing, your approach is the best, no need to tape the Z flashing just get it behind the WRB. If the windows well protected by an overhang, the head flashing detail is not critical, you can just keep it as is.
Hey Josh,
It's always tricky to get the flashing right when doing full window replacements with siding remaining in place. I've seen a lot of belt-and-suspenders tactics born out of necessity in these cases. This FHB video shows a pretty sound process: http://www.finehomebuilding.com/2013/10/28/video-series-retrofit-a-flanged-window