I'm familiar with the concept of sistering ceiling joists to make them appropriate to hold a live load as a floor, but I've found the various joist calculators and tables either wrong or confusing. I'm in British Columbia so I'm hoping to get an answer specific to our residential code.
I currently have 2x4's every 16" on centre for a span of 12ft. Here's the PDF for BC's structural code. If I'm reading it correctly, I believe I'd need 2x8" joists at "select structural" grade for northern species. I might be able to use spruce 2 grade considering that this is a sistering application and the existing 2x4s will be glued and nailed to the new joists - I'll confirm with a structural engineer at some point. Can anyone confirm that I've read the tables correctly?