Construction question - sheathing under open soffit

[JasonMcElroy]

Hello,

I'm building an accessory building in my yard and have a question for the many experts here I've enjoyed learning from over the years.

Background

• 10'x12' footprint slab-on-grade
• Shed/skillion roof at 3:12
• 2x4 framed walls with 15/32 OSB sheathing
• 2x8 rafters with two flying rafters on the sides
• Inner rafter pair at sidewalls are set flush to 2x4 wall framing
• I sheathed up to the top of the sidewall top plates but did NOT sheath the rafters
• All rafters are tied to front and rear walls with hurricane ties and full nailing
• Roof overhang will be open soffit

Questions

• Did I need to sheath all the way over the rafter to the roof deck?
• If yes, is the reason for structural integrity or just to have uniform surface for siding?
• If yes, can I just cut some OSB and install as packing to come flush with existing wall sheathing or does the sheath need to bridge the rafter with the wall framing?

Thanks much for your time and consideration.

Jason

 

[jack stand]

It's good to avoid creating even the tiniest ledges "up there".
Birds will be building nests on any little ledge (bird **** all over the wall below) and I would suggest some sort of closure.

 

[PCustoms]

How are you going to trim/finish the wall surface in your open soffit?

 

[JasonMcElroy]

Thank you both for your input.

@jack stand Definitely will avoid a ledge. Am just trying to decide on whether space next to rafter needs to be packed out to be flush with sheathing and whether it's OK to do it with piecemeal leftover OSB drops or whether there is a structural need to bridge the rafter and the wall framing.

@PCustoms I plan to do lap siding with Hardie board. Not sure how trimming is done under eaves/soffit so I've been searching photos, articles, and checking out houses in the neighborhood.

If it's not obvious . . . this is my first time doing a project like this. I've owned old (really old in some cases) homes in the past and have done plenty of repairs & maintenance. Have also helped and learned from some great friends and neighbors in the past who do this for a living, but sadly many are no longer around.

I am having fun with the project. I'm also learning a bunch. It is fascinating how many previously unexamined details become apparent when you decide to build something from scratch yourself.

Thanks.

Jason

 

[PCustoms]

My recommendation would be to close in your soffit, it's going to simplify a lot of things

 

[ericm]

Enclosed soffits are better for fire safety too. In fact some insurers here are requiring them.

 

[BillK]

If I am reading your question correctly I cant see why you would want to put sheathing on the actual rafter. Is this where you are talking about ?

 

[jack stand]

If you really don't want to have soffit, run your siding and and trim or termination of the top of the siding, then build out the last rafter to whatever you need to apply a finish board in between the fascia blocks that doesn't leave a ledge.

 

[jack stand]

Remember, depending on the level of your desired finished look, you will be looking at the underside of your roof (without soffits) in these overhangs.
Typically OSB or not any prettier cdx sheathing.

 

[JasonMcElroy]

I'm sold! Seems like more work and trouble keeping the eave open than just closing it. Will do.

Thanks for your input.

Jason

p.s. - @BillK Yes, that was the spot I was questioning.

 

[Chris705]

If you like the look of the open soffit for your shed and/or perhaps you’re matching the detail of another building on your lot, then I say proceed with what you’re describing. Yes ideally for a home or conditioned space you’d want to tie the sheathing up into rim board space…. It would have added structure to tie walls and roof assembly together and cut down on possible source of air leakage. Because you have already quantified you have addressed the structural aspect of not running the sheathing up into the rafter space that’s not a concern now to piece the sheathing up into these areas. Others have pointed out the difficulties of having to piece the siding up into the open soffit. Exposed rafter tails offer a classy bungalow look and depending on your location could fit right in. Tounge and groove boards left exposed and painted/stained look nice. In my area however they offer a great area for bees and wasps to nest….best of luck on your project! Remember if you are doing this project on your own then these types of details are what could set your project apart from others, you may have time to spend on these labor intensive details. Perhaps others are not aware of what exactly an open soffit is all about or that they would never consider such a detail on their own project…. Don’t dismiss details prevalent in your area.