If you can feel some deflection you have two options.
How to install wooden floor joists.
Find a metal joist hanger that can support the new joist you re installing.
In cases where greater open spans are needed framers often use joist hangers which are u shaped hardware pieces that are nailed in to accept hold and support flooring joists.
Besides solid wood joists systems such as i joists and flooring trusses provide other options for consideration when it comes to installing a flooring framework.
Engineered wood floors are easy to install and resistant to moisture making them a great alternative to traditional.
Make sure you ve got the right amount of flooring for your space.
Make sure the bottom of the joist is sitting on the hanger without any gaps.
The rim joist sits vertically on top of the sill plate along the outside of the frame to create a lip for the main floor joists.
Both solid wood and engineered can be fitted this way.
You ll use the same size lumber to assemble the rim joists as you will for the main floor joists.
If raising the floor height is not a problem you can install a layer of 1 2 inch plywood over the existing 3 4 inch plywood.
Join the ends of the boards over a floor joist where possible avoiding joints that form an h.
Align the edge of the board with the chalk line and drill pilot holes down through the hardwood plank and into the sub floor and joist.
Step 5 finishing up.
Face nail each board at the point of every joist and set the nail with a nail set.
Once you have done this you can replace or install your floorboards normally confident that you can rely on your joists to hold your floor together.
Wood floor fitting over joists to answer directly to the question yes it is entirely possible to install a hardwood directly on top of the joists.
Install hardwood floors perpendicular to the floor joists parallel to the longest wall leaving a inch expansion gap around the perimeter.
When possible begin installation from the straightest longest wall and install the flooring perpendicular to the floor joists.
Install joist hangers for added strength with a hammer and nails.
Keep joints that line up at least two rows apart.
Fit the joist hanger around the joist.
The other option assuming you have access to the open joists from below is to install 2x4 blocking between the joists 24 inches on center.
For most jobs 2 in 5 1 cm x 10 in 25 cm boards are an ideal size.