Attic insulation

[TonyTheTiger]

So I am going to have 2x6 ceiling joists, with a gambrel roof above. Span is a little less than 15 feet, spaced on 16" centers.

Could I just put Kraft backed fiberglass in the cavity, then puthalf inch osb on top of that, then blown in cellulose to, say, r50 or so total above the plywood? The plywood would have no breaks except for a bathroom fan and an access door.

 

[Mr. Inspector]

depends what code is being used there and what climate zone you are in. Is attic ventilated? are there baffles at the exterior wall?

 

[SCBO1]

Will the ceiling by OSB, plywood or drywall? Trying to figure out why you need batt insulation? No storage?

 

[TonyTheTiger]

I'm afraid of sagging drywall if there is too much insulation weight directly on it.

 

[mtlogcabin]

5/8 drywall on 16" center support should have no sagging problems due to the weight of the insulation. Typically about 20" thick for blown in fiberglass.

Drywall sagging in the past typically resulted with too much water applied to the finish. Popcorn and sponge finishes come to mind.

d. Three-eighths-inch-thick single-ply gypsum board shall not be used on a ceiling where a water-based textured finish is to be applied, or where it will be required to support insulation above a ceiling. On ceiling applications to receive a water-based texture material, either hand or spray applied, the gypsum board shall be applied perpendicular to framing. When applying a water-based texture material, the minimum gypsum board thickness shall be increased from 3/8 inch to 1/2 inch for 16-inch on center framing, and from 1/2 inch to 5/8 inch for 24-inch on center framing or 1/2-inch sag-resistant gypsum ceiling board shall be used.

 

[TonyTheTiger]

Code says at least 1/150 of attic area for venting. 60x40 is 480 so that would make it 3.2 sq ft, or about 22 inch square.

 

[TonyTheTiger]

I was planning on half inch. And 16" spaced 2x6s (span is about 14' 2").

 

[ADAguy]

Ohio, it appears you have nothing but time on your hands to justify your proposed DIY actions, so why ask us if you already believe you have the answers? Are you permitting this project, then follow your local code as a starting point.