I’m building a utility building this summer and have been stewing about the pros/cons of having an attic above the 24’x24′ main space v. the consequence having to have a post in the middle to support a beam down the center of the joist span. I was shying away from the cost of an LVL beam. In the meantime, they started tearing down a local school built in the 20’s and are selling the floor joists, which are Doug fir 2×16 24′ long for $0.75/bf. They are in excellent shape and of high grade (I’d say the average would be #1). I started thinking about laminating a beam out of these, and dug out the Encyclopedia of Wood and started working through the engineering calculations. I got an answer that a 3-ply beam would be just barely sufficient for the load, but I’m not 100% comfortable I did it right. I don’t expect this floor to ever carry anything close to the design load, so I’m not too worried about being close to the limit.
So, the question is, does anyone have the tables to tell me how many of these planks would be necessary to create a beam that could carry a design load of 576 pounds per lineal foot (40 psf live, 8 psf dead, 6′ either side) over a simple span of 23.5′? Before anyone tells me to check local code, I’m in a rural area without structural codes that apply to this building, but I still don’t want to undersize the beam. The actual size of the planks is 1-5/8″ by 15.25″.
Any help appreciated,