Mezzanine/Loft build - minimize vertical posts

[07ketnec]

I'm planning to build an 18'x18' storage loft in my Morton shed, approximately 9-10 feet off the floor. My goal is to minimize floor posts, ideally having only one corner post as a primary support point (see photo).

The loft will be for typical attic storage items like holiday decorations, kids' toys, and general household decor – nothing exceptionally heavy.

My main question is: What size perimeter beams would be needed to safely support this area with only one corner post (2x10, 2x12, LVL)?
Once the perimeter beams are set - what size joists would you suggest?

 

[billconner]

Design for 30 psf. 2x12 joists 16 OC. On one post side, let your lumber yard size and lvl for 18' span and 315 plf. (9' x (30 ll + 5 dl). Simple to do same on wall side, or add a post like diagram and get lvl for same load at 9'. I'd probably use joist hangers. Bridging would stiffen it up some but not necessary.

Youv got a point load of near 2835 pounds under post. Don't know slab thickness and base but you may need to add a footing.

 

[fugitivealien]

I'm not sure where you were on this, as it's an older post and I don't see any other activity. However, if you're considering LVL in the project, you could run a single laminated beam across the entire space. Then you would only need posts to support on either end. Online calculators can assist with beam size calculations for the load. Then frame in as much loft area with joists. I'm not sure the exact dimensions of your shed, but if it's 24', you're looking at (3) 1 3/4" x 11 7/8" 2.0E grade beams glued and screwed together, a 2x10 ledger board along the wall, and 2x12 LVL joists 18' long. For anything beyond that, you're looking at W10x26 steel beams and 6x6 support posts.