Theoretical Problem - F=ma

I was thinking about this today:

When a force acts on an object, the object exerts on equal and opposite force - Newton's third law. Imagine this situation:

I am breaking down a wall with a hammer. I begin hitting the wall gently and this wall doesn't break. I then hit harder and the force exerted on the wall increases. As I'm hitting the wall harder, the wall begins to crumble and break.

What I want to know is:

- Does the wall have a certain threshold value at which point it cannot exert a force opposite and equal to the force I hit with and begins to crumble? The harder I hit, the more I exceed its threshold value and the more it crumbles and breaks.

-Why does the wall not fall down completely if I exert a force just above this theorized threshold value? Is it due to friction forces in the planes of atoms? Is it due to the composition of the wall itself? Or is it due to the way atoms are arranged in the wall?

I think this is less to do with the ability for the wall to exert forces, than just simply the bondings of molecules in the wall (be they chemical or otherwise), not being able to withstand the force you applied. Obviously, if you had an infinitely strong wall, you could apply a strong a force to it as you want and it wouldn't break (the unstoppable force and the immovable object). Also, the wall doesn't all fall down, because your force applied isn't exerted on all the wall, just part of it. If you had a hammer the size of the wall and hit it then ,obviously, the whole wall would fall down.

And just as an extra, F=ma isn't Newton's third law of motion. It's his second.

I suppose the third law could come into the bit where you end up breaking your hammar though =P

Well I would say that Newton's third law applies here more than F=ma