We see a lot of structural mezzanines in our business in a range of facilities. They range from professionally manufactured to home-made, with quite a few fabricated by a local shop. It’s a good business for the fabrication shops (although maybe not so much for end-users, given the potential pitfalls), and if you go that route, you need to be sure your mezzanine fabricator is complying with OSHA & local safety regulations, particularly on guard railing, stairs and gates. You also have to look at local building codes. If your fabricator doesn’t routinely work with mezzanines, this is something you’ll have to do on your own. It’s not something to dismiss lightly.
The best policy is to look at established vendors if you don’t want to micro-manage the details of building permits, code compliance, and OSHA’s blessings.