Hard to say how many plies would be needed - depends on the depth and your design loads, and how your floor is framed. Thanks again- you all were GREAT!RalphKen Caryl area, Colorado, *Boss- You seem to be a regular here....Sorry, but I have to steal time at work to check messages. I will be adding a kitchen/dinning room bump out on the back of our straight faced 2 story colonial here in Denver Colorado. Again you're looking a larger-than-typical, but not ridiculous footing. This may be your best bet, as it could be recessed into the roof, and your floor system hung off the side of it. *Whoa. A glue lam is not going to work for that size span. Then temporarily support existing floor load and install 12 x ?? I like defending us DIYs here against the pros. *Ralph - Are you still around, or did you ditch us ?? Filled the cores of the 12 inch block foundation with 4000 psi concrete to the footer.Cost me about $250 to have three beams sized and downloaded. So you would have to wrestle a two ton piece of steel into an existing wall (while still supporting the existing structure from collapse. The folks here like to stretch the limits and test new techniques, so they want to find a way for you to do what you want to do, but I'll volunteer to be the a**hole and tell you to forget about it and find an architect or even a friend with an eye for design to hide the posts or make them an attractive element in the design.Good luck-Randy. Because these floors support the lightest loads, they require the fewest support columns and the smallest LVL beams. So, I asked the guy who just rebuilt the place next to mine, and he recommended a very good engineer, who looked at my calculations and said that I had gone into far more detail than they want to see. I would go with a steel I-Beam over an engineered wood beam if cost is a concern. I agree with Jeff that you will probably need 4X3X3/16 T.S. Your reaction might be even more, depending on the snow load required in your area of Colorado, the width of your house, and how your floor is framed. *while you're out looking for engineers .. run your addition by a good architect....the 10 x 30 with a shed roof sounds like it could use some TLC...good contractors are still a dime a dozen.. but good design is a treasure beyond worth(and bad contractors are legion)b but hey, whadda i no ? Compare the three numbers. Ralph - This is for planning purposes - DO NOT ORDER A BEAM BASED ON THAT COMMENT! Will your foundation support that ? Of course, it's only been 18 years or so since I built it, so it really hasn't stood the test of time yet. When your county inspector questions your drawings you'll pull out your load calculations, and that book. You don't want them. Say a C15 x 40 bolted to each side of the upper floor wall studs and TS columns cut into the existing wall to footings. But be careful. Speaking from the standpoint of an aircraft structures engineer, that's one big-ass clear span. *I want a 40' motorhome that can go 200mph....Oh, and I want it to be affordable and safe. I do not want a supporting post in the way. What’s the smallest dimensional thing I can get by with? There was no wood in between the steel and concrete columns and the columns were reinforced.near the steelhead stream,aj. Span Tables; Toggle navigation. that is assuming your home is 24' wide w/12/12 pitch + the 5' tributary of the addition w/ a 4/12 pitch w/a 40# snow load & a 10# dead load and with a 40# live load & 10# dead load w/a 12' second floor tributary width and a 100# dead load for 2nd flr. Thx' for the advice.RA, *Matt, et al:As a first- timer in the Breaktime, I am blow away by the response and advice.