Two nails in my hardwood flooring keep popping up:
I have knocked them back in, but because of a bit of flex in the floor, they work their way back up. What should I do about them? Is it best to just pull them?
Use lost-head screws. These have heads small enough that they will pull down into the surface so you can cover them with a dab of filler.
There are many types, for different purposes, but all have this tiny head that will pull down below floor level. Often they use torx or square drivers so they won't cam out when driving. Drive them at an angle for even better pull resistance.
This may be another of those terms that doesn't cross the Atlantic well. If I search "lost head screws" I get a lot of hits, all in the UK. If I search "finishing screws" I also get a lot of hits, but a high percentage of them are in the US.
Interestingly, if I search "lost head nails" vs "finishing nails" in the UK I get the 'correct' nail [ie the one I thought I was looking for] for lost head, but I get the wrong nail for finishing.
I'd pull them out and see if the floor squeaks or flexes. Maybe you don't need them and can fill or ignore the holes.
Otherwise, replace them with ring shank or spiral shank type nails...as suggested here:
"Two nails in my hardwood flooring keep popping up: I have knocked them back in, but because of a bit of flex in the floor, they work their way back up. What should I do about them?"
Civil engineering answer:
The problem is not the nails, it is the floor flexing. The friction between the nails and the wooden restraint structure has been overcome by the force of the flooring pulling against the nails. Fix the underlying cause of flexural movement and nails will not be an issue ever again.
Using screw threaded fixings will not relieve the stresses causing the problem but may actually cause damage over a longer period.
Injecting a low viscosity epoxy filler, that will harden, through the nail holes into the underlying flexural space may be the best route in solving the flex.
How do I fix popped nails in hardwood floors?
Note: this answer is intentionally literal instead of pragmatic.
Hammering them back in same hole wont hold
Hammer the nails at 10-30 dgr angle to drive the nails, that will stop them from coming out. That might take some practice.
Use a nail sinker tool, so to drive the nails just below surface and not to keep banging/damaging on the floor.
Fill the old nail holes with wood filler
If you do not want to do all above, go to store and get longer nails.
Using glue suggestions:
Glue will not flow down the hole to the underfloor, it will mostly get soaked up at the top portion.
It will hold the nail and fool you, since it is not holding the floor to the underlayment.
Result, squeaking floor.
Seems like no-one has mentioned pulling out and using bigger nails. If you're certain there are no pipes or wires underneath, in the joist, and the joist will take longer nails, great. Thicker nails would also do the job, same length as originals, if you're not sure. Otherwise, two or three toothpicks in the holes first will help. Or, knock the nails in at a crazy angle, avoiding the holes from where they came. Cheap and cheerful.