Floor joists and subfloor
Now, you are ready to start building the subfloor structure on top of the foundation with flooring materials. You will start by putting the sill plate down on top of all the anchor bolts. Drill holes where all the anchor bolts are and screw the sill plate down evenly. It will go all the way around the top of the foundation.
After that, you will put up the rim joist, which is usually a 2X10 on its side, all the way around the outside of the foundation. See pic
Next, you'll put the floor joists in and nail them through the outside of the rim joist for extra strength.
They should be on either 16" or 24" centers depending on
what the inspector says. I'd prefer 16" centers for extra strength.See
pic.
While the floors are open like this, you can take advantage and run some of your plumbing lines.
Once the floor is on it will be more difficult to get
long ABS pipes or copper pipes into the crawl space. You can even run
some of your Electrical and Network cables while it's open.
Once the joists are in place, you can cover them with the floor material. It's called subfloor because there will be a top floor that gets put in with the finish work.
A good material is 5/8-inch plywood or waferboard. This is where you see if your foundation is in square or not. If it's not in square you'll be cussing a lot throughout the whole building process. The sheets won't fit together very well and there will be a lot of gaps.
That's just one of the many reasons why it's so
important to get the foundation perfectly square before you pour it.