You will find two floor systems to contemplate: Joist floors and post and beam floors. Reviewing disadvantages and advantages of each can help you make the correct selection consistent with your goal of having a well- constructed house of your own.
Joist floors are generally 2×10 or 9 ½” I-joist at 16 inches on center together with sill plates of the concrete base and 6×8 beams on 6×6 pressure treated posts. Commonly, subfloor is 4×8 of 3/4″ plywood or OSB (Oriented Strand Board) panels.
Post and beam floor framing consists of 4×8 beams at 4 feet on center along with pressure-treated 4×6 posts inside the base. For the subfloor on top of 4×8 beams, some contractors use low-grade 2×6 tongue and groove. On the other hand, the favored option is 4×8 of 1 1/8″ tongue and groove plywood.
Joist framing can sit inside the base, but top flange joist hangers are needed to hold the floor joists up. This set up is debatable due to possible differences and movement of the joist hangers. If you need the floors to be the foundation, post and beam floors might be the better alternative.
To clarify “floors inside the base,” the subfloor is on top of sill plates and the remainder of floor framing is inside the foundation. One reason why you should select post and beam floors will be to get the floor closer to the standard to remove up two measures to your house entry for disabled people.
The insulation batts fit snugly between floor joists at 16″ on center. With the post and beam system, insulation batts don’t fit as well because the width of insulation batts is either 16″ or 24″ wide. Hence, two 24-inch insulation batts are desired to cover at four feet on center between beams. Additionally, insulation batts stapled at the underside of beams and are held up by stringing wires or cords across. At 4 feet on centers, cords or wires have a tendency to sag conquering the goal of insulating material that is to keep the heat and the cold outside in and making the insulation batts free.
Another drawback for the post and beam floor system is insulation batts will partly obstruct the base ports. Insulation batts will limit the air flow between the base ports because the floor framing is inside the base. Your crawl space needs ventilation to get it dry and fine which, consequently, keeps forms away. The base ports can be constructed lower, to counter the restriction to air flow but this will demand the concrete walls to be higher off the level.