Solid Hardwood, Engineered and Laminate Flooring - How exactly can a tounge and grove floor expand when it is being nailed down?

How does expansion happen when the floor is secured at regular intervals?
Thanks:
Sonny

Try making a tongue and groove in 2 sponges and nail it down at the corners.
then pour water on the sponges.
What is going to happen? They will expand in every direction they can.
Kind of similar principle but slightly different dynamics because the internal fibering is different. They expand to different degrees of course, but the water has to go somewhere.
The damge is caused when the sides work up against each other rather than moving together.
PS The sub floor also expands. If you want to get picky about it, the 2x4's in the wall also swell, so the wall moves toward the center of the room.
It is all making the forces not be destructive to the floor's performance.

Also consider this, if the water balance was in equilibrium in all the wood and the temperature and humidity never changed, the gap would have to be quite small, but then you would have to make sure the barometric pressure never changed too. It could get more complicated.
3/4ths of an inch is not much space, just leave a nice comfortable margin for having a floor that looks great and does not get damaged by the normal forces of life.

That's all partially true.

Wood expands with moisture across the grain much more than with the grain, by about 5:1. Nailing(more often) in the tongue limits some swelling.

Thus T & G is usually not a problem due to swelling. Shrinking is usually the culprit on indoor installations.

fred

And the tongue is nailed, but the groove isn't. The groove is what moves more.
Mike