Employ a stud finder to find a joist.
How to find joist under floor.
3 look for a second row of nails running.
Turn the stud finder on.
Most people use a stud finder to locate studs through drywall but the same principle applies when looking for a joist in the floor.
Kneel down on the hardwood floor and gently tap the head of the hammer on it paying special attention to the sound it makes.
Look closely at the carpet near the yellow tape measure.
Look at the subfloor and find a row of nails which are attached to a joist.
The nails tell you where the first joist is and which direction it runs.
Move the hammer to the left or the right until the sound changes from hollow to solid.
A number of test hole locations are within the photo but they are not visible.
This indicates that you have located a floor joist.