Running electrical wire through the channel between ceiling joists is generally easiest.
Run wire above ceiling joist no attic.
If you drill holes in the joists and run wire through those holes you ll be disturbing the insulation.
The access is 14 because it s constrained by the 16 centers of the ceiling joists.
If you have an existing drywall ceiling however or you plan to finish out the ceiling with drywall you must make.
If there is access above the light in an attic or kneewall space you can remove the wire from the existing fixture box and install it in a junction box.
Worst can you open the ceiling 5 inches from the wall and work from there.
In addition your light fixture may require mounting to a ceiling joist or to two short blocks nailed.
If there is any attic space at all or you get lucky with the joist bays you will likely be able to fish a.
A 3 inch strip of drywall is enough to run receptacles around a room.
You can then splice on a new piece of wire make sure it is the same wire gauge and run the new piece from the junction box back to the fixture box.
For vertical work you can cut about 6 inches below the wall ceiling joint drill through the top plat and then fish from the opening ion the ceiling.