I want to build a loft above my two car spaces in the garage.

It is 20 feet wide. Length is flexible depending on wood suggested. 8, 10, 12, 16 feet etc. There will be walls on three side but I don't want it supported by the walls. I want it supported with it's own 2x4 framing to the floor? or 4x4 posts.

I'm trying to figure out how to span 20 feet in the garage without any posts in the middle. I'd hate to have a car knock it out some day.

  • Ok Longneck answered my first question. 2x12's across.
    – Dan
    Commented Apr 18, 2014 at 19:30
  • 20' clear span is quite long, you may have difficulty finding lumber in that size. Lots of garages have columns between the car bays. If you're worried about damage from cars, you could build a protective case around the posts.
    – Hank
    Commented Apr 18, 2014 at 20:53

1 Answer 1


You're basically asking how to build a free-standing deck. According to this calculator, you need 2x12 joists on 12 inch centers.

If you don't already have one, I suggest buying a deck building book from the hardware store. It will tell you exactly what you need to know.

  • yes thank you. That's another way to say it. A free standing deck with no center support. I like the calculator.
    – Dan
    Commented Apr 18, 2014 at 19:25
  • There is different code requirements for a deck vs. a house. Also a deck has nothing above it.
    – DMoore
    Commented Apr 19, 2014 at 4:39
  • If the 2x12s are too tall, you could look at using LVL lumber. It's more expensive but can carry more load. Commented Apr 19, 2014 at 20:54

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