Framing exposed rafter tails, sistered to common rafters
I would like to have exposed rafter tails on our addition. But, I don’t want to expose the spruce common rafters I’m using to the elements. I have some full dimension 2″x6″ red cedar I would like to sister on to the common rafters, so that the exposed tail will be rot resistant.
I attached a drawing. The tails are ⅔ in, ⅓ out. They are dropped 1 ½” to allow for t&g car deck below the roof sheathing (nicer to look at from below). There’s blocking to accept the end of the sistered rafter tails. This is all in an unconditioned attic space.
Some potential issues: the seat cut is the full 5 ½” of the top plate. This normally wouldn’t be allowed with the 8-12 roof pitch, because the birdsmouth would be more than 25% of the rafter depth. But is that an issue in this context? Shouldn’t the common rafter still have it’s full strength?
Other issue: the wall does not have a double top plate. The sistered rafters won’t bear directly on the studs.
The height of the overall assembly also makes it easier for me to match the eave line of the house we are adding on to.
There are no building codes here in rural Alaska, but of course I still want it built correctly.
thanks for taking a look.
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