Construction is coming along, last night I noticed that the Entry Door is being propped open with a 2x4 under the bottom edge, between the door and the slab. Since 2x4s are really 1 1/2 x 3 1/2 that means that if I put down a 3/4" subfloor and 3/4" wood floor the Entry Door won't open or close. It's a steel door so it can't be shaved. Do I make the builder re-hang the door so I have clearance or can I use 5/8" plywood for a subfloor? I did a search but didn't find my answer.

If you are planning on installing a solid, 3/4" thick wood floor, you need a 3/4" wood subfloor MINIMUM as a nailing base. The subfloor can be floated, glued, screwed and nailed with a moisture barrier underneath it. If the clearance between the slab is and the bottom of the door is less than 1&3/4", you will have problems. As it is, even at 1&3/4" clearance, you will still barely clear the proposed floor and not have room for an area rug. The easiest way to resolve is your idea. Have the builder re-hang the door. He may not like it but it is doable.