I'd like to double my ceiling joists to make my attic space easier to work in (for electrical/plumbing) and for lightweight storage.
Status Quo: 2x4's (actual size) spaced 16" on-center running the width of the building uninterrupted, with the ends resting on top of the wall top plate. Each joist is strong enough to support my weight (~175lbs ) concentrated in a ~1' segment of the joist, and there isn't much deflection either.
Goal: Reinforce the joists and lay down a wood subfloor (OSB, ply, etc.) so I'm not tiptoeing on joists whenever I'm up there.
Plan: "Sister" or double the ceiling joists with 2x6's or 2x8's with the ends resting on the wall top plates then lay the subfloor on the new joists.
Question: I understand that there are requirements for doubling joists, including how frequently they need to be fastened, but does this plan make sense overall?