# How To Sheathe a Wall Under Eaves?



## Lascaux (Apr 17, 2012)

*Wall Assembly To Be Sheathed and Insulated in Climate Zone 5A*

Here is a drawing of the wall assembly:









I think that I need to sheathe above the brick and up to the top of the joists before I install insulation in the side attic floor. How do I best do this in climate zone 5A?


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## Windows on Wash (Aug 30, 2011)

Those joist bays need to have rigid blockers installed in them and them foam sealed from the sides and top. Make sure there is a proper vent space to allow the soffit air to draft up along the roof line and into the attic.


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## Lascaux (Apr 17, 2012)

Windows on Wash said:


> Those joist bays need to have rigid blockers installed in them and them foam sealed from the sides and top. Make sure there is a proper vent space to allow the soffit air to draft up along the roof line and into the attic.


Thanks, WoW. I plan to block the joist bays with Foamular 250 both at this outside wall and at the point where the joists go under the finished attic room:








I am considering sheathing the upper part of this outer wall with a continuous air barrier of sealed Owens Corning Foamular 250. This sheathe would start just above the level of the brick cladding. I would retain the vertical gap between the brick cladding and the fiberboard so that the original construction of the first floor below would not be altered. I would allow air to continue to enter here. 

The sheathing above the first floor would provide a barrier up to the (Provent) rafter vents. I would insulate up to to above the joists and then block both between the joists and up to the rafter vents on the inside of the wall. Is this overkill?

Also, In order to create an acoustic barrier between the finished attic room and the family room below, can I fill the joist bays below? There is electrical running through the bays. It's rubber, 2-conductor cables into j-boxes. It is unlikely that I will be able to replace the wiring below this floor.


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## Lascaux (Apr 17, 2012)

*1.5 Story Under-Eaves Wall Sheathing*

I'm working on answering my own question...

"The Guide to Attic Air Sealing" on buildingscience.com has some pertinent information in the section on a Two Story Wall (pg 34-35).


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