Ok, so yall may have seen my barn thread and here is what I'm trying to figure out. I'm not new to framing but I sure aint a professional. I'm knowledgeable enough to layout steps and rafters, walls, T's, corners, jacks, and headers. Inside my block barn I'm framing walls up around the perimeter. Its roughly 17x21 feet. I want to span the width in the center with a beam to tie joists on both sides to. My actual beam length doesnt have to be 17 feet, I can get by with 16 feet because the way the tile block was laid to account for the tier poles by the time my stud wall gets about 5 feet high the way the block is laid changes making the space of the room roughly 8 inches wider from 5 feet off the finished floor to the roof. I want to do all my framing of the second floor, floor with 2x10 southern yellow pine and this beam I'm asking about I want the same width as the 2x10. In other words I want a flat ceiling downstairs. My idea but I'm no engineer is to span it with 4- 2x10's with 1/2" plywood between each one and staggering the plywood joints. The second floor load isnt going to be all that high especially in the center. I would consider it a live load of a bedroom which is 20 I think instead of 40. I know my load isnt going to cause little if any deflection but I dont want this beam to sag because of the 16-17 foot span. LVL's are an option but I haven't priced them. If I can go with the 2x10's I'm looking at about 60 bucks for a beam versus 2 or 3 LVL's at a cost of???? At this point steel is not an option for cost reasons and reasons that I am doing this myself . Help is very limited.