Sheeting/ insulating Garage ceililng and walls

[panski master]

I have a bi level house and my garage ceilling is half rocked and then is rocked straight up to the very top of the roof for fire code i guess and is not insulated and no vapor barrier behind it. I want to sheet the ceiling and insulate it. Can I put my poly up over the sheet rock and open rafters and then sheet my ceiling with OSB and then insulate? It would be making a sandwich with poly between the rock and OSB for a portion of the ceiling. I don't want the mess of taking out the rock and then putting up poly. Any thoughts or suggestions. I would also be sheeting my walls with OSB after. Thanks, Keith

[Tom7227]

It would probably violate the fire code.

[EyeChsr]

poly the ceiling and sheet it leave the rock as is.

[cavalierowner]

I have a bi level house and my garage ceilling is half rocked and then is rocked straight up to the very top of the roof for fire code i guess and is not insulated and no vapor barrier behind it. I want to sheet the ceiling and insulate it. Can I put my poly up over the sheet rock and open rafters and then sheet my ceiling with OSB and then insulate? It would be making a sandwich with poly between the rock and OSB for a portion of the ceiling. I don't want the mess of taking out the rock and then putting up poly. Any thoughts or suggestions. I would also be sheeting my walls with OSB after. Thanks, Keith

I'm having a little trouble visualizing what you have, but keep in mind that the poly vapor retarder has to go on the warm side of any continuously heated space. IE, if the sheetrock you have now is enclosing a bedroom or something, then any vapor retarder has to be on the bedroom (heated) side. Make sense?

[Surface Tension]

The vertical hung rock is a fire break between the garage and the attic in the house. That will be an unheated and no vapor barrier is necessary there. The rock on the ceiling in the garage should have a VB between it and the bottom cord of the trusses.

If it doesn't I wouldn't lose and sleep over it. Don't lay poly on top the bottom cords, just leave it.

Before you finish the rest of the ceiling insulate first. Then your VP and rock.

Substituting rock of OSB, you might want to check codes there. Personally I don't like it because it looks unfinished. You'll need to keep the spacing between sheets or else it'll wave from temp and humidity changes.