I am planning to remove the wall between my living room and dining room. It is a load bearing wall and I am planning to build my own beam to span the opening. The wall is 17' long. I want to make my beam out of plywood cut, glued and screwed together. I want it to be about 8" thick but I am not sure how high to make it. This is a ranch style home with a truss system for the roof. Trusses are 2"x4" 24" on center. In my estimation a beam of 8"x10" should be enough to support the roof. Anyone have any other thoughts on this?

Why go to the trouble of making an inferior beam yourself, when products like LVL beams are readily available> Further, you will get engineering help in selecting a size. "In my estimation" is not accpetable for beam design. A question: if you have trusses, why do you think that wall is a load-bearing wall? Trusses are normally engineered to span from outside wall to outside wall, and any partitions within the outside walls are non-load-bearing.

Your "plywood beam" will not perform acceptably, and I say that even not knowing its span and the loads that will be on it. However, it's possible that you don't need a beam at all.

Thank you for your answer. I am not a builder (as you can tell) and any help I get is very valuable. I will check on the LVL.

Richard's right, LVL's are cheap and better than beams that are made from lumber or plywood by a long shot.