Looking for an exposed rafter tail (vented attic) detail
kewilli6
| Posted in General Questions on
Hello Legends! I’m looking for a wall-to-roof detail that illustrates exposed rafter tails to a vented attic. The rafters will sit on an air-sealed “box” that I describe below. I haven’t seen this specific method before but was steered this direction since we have a large complex roof.
For context, my Georgia home will be a single story. My plan is to run all HVAC in open-web floor trusses and install 5/8″ zip-taped OSB on top the trusses to create an air control layer. I’ll just blow cellulose onto the attic floor.
Any advice or warnings are well-appreciated. Thanks!
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Replies
kewilli6,
What I did on this house and several others is install 2"x blocking between the rafters that is 1 1/2" shorter than them, and use a piece of U-shaped perforated flashing to fill the space above. I keep the the blocking out far enough that the cladding can butt up against the bottom of it. That avoids there being a ledge which accumulates dirt and bird nests.
That looks great. Thanks for the input!
kewilli6,
Excuse the window placement. The client and builder got together once the design was complete and made a bunch of changes. I have mixed feelings about how it turned out.
After doing more digging, I found some other threads here that offered additional help. I also found this older detail from Cor-A-Vent.
kewilli6,
I like to cut the top of rafter tails down so that you can run the plywood sheathing over the T&G. That helps plane out the two materials, as usually the T&G is thicker than the roof sheathing. It also gives you more backing for the roofing fasteners, that otherwise are visible from below. Even then you have to be careful about the length of nails or screws you use on the overhangs.
Slick!
CC,
And easy to do if you are using applied rafters on a trussed roof by just dropping them.
Thanks for your post! Yes, I saw that on a recent Build Show video with Matt R. I'm definitely planning to do that. Do you have any feedback on my thought to create the "indoor" space by air sealing above the floor trusses before the rafters are set? I'm curious if inspectors will have a problem with rafters sitting on the decking instead of an actual top plate. I'm planning for them to align with the floor trusses where possible.
Matt's video is here: https://www.youtube.com/watch?v=Lm8Afm7He4U&list=WL&index=4&t=34s
kewilli6,
It's a good detail - I think both Ben Bogie and Michael Maines have used it. The only downside I can think of is cost.
There is no problem with the rafters sitting on the floor not top plates, but If there is no ridge beam or rafter ties, they will need good attachment to the floor to counter horizontal loading.
Awesome, thank you. I'll post a model mockup for feedback when I get it designed 🍻