Installing a floor in a smaller home is easier than a big home because you don't need as many girders to compensate for the wide span up the middle of the floor. The floor joists and subfloor rest on the foundation. Actually the joists are nailed to the sill plate which is bolted to the foundation.
The strength of the floor will rely on the 2X10 lumber on its side and nailed to the plate on the foundation. You can also use manufactured floor joist made of composite wood. They work just fine and are a little cheaper.
We'll start out by installing the sill plate. This is usually a 2x6 that fits on to the foundation wall. Holes are drilled every place there is an anchor bolt. This wood should be pressure treated lumber to discourage termites.
The sill plate needs to be flat against the top of the foundation when you tighten down the nuts on the anchor bolts.
These photos are kind of fuzzy. You can see how I applied the sill plate all the way around the top of the foundation and up the middle girder as well.
The board that you lay on it's edge all the way around the outside of the foundation wall on top of the sill plate is called the rim joist. You can toenail this to the sill plate at an angle.
Once we have the rim joist attached to the sill plate we can start to put in the floor joists to hold up the subfloor material.
These are really easy to attach because you can nail them from the outside of the rim joist to make a secure connection with nails or screws.
Floor joists will need to be a certain space apart so that the plywood can be attached. For example, most floor joists are on 16-inch centers. This makes it so the 8-foot sheets of plywood fit without any gaps.
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