Terraria – In Terraria, what differences are there between stone and wood when used to build a house

As of Terraria 1.6, there are four dedicated Ammo slots in your inventory. Applicable ammunition in these slots is consumed first, from the top slot to the bottom slot.

After that, and in previous versions of Terraria without the Ammo slots, it uses the first type in your inventory starting at the top-left and working right. So the highest arrow is used, and when tied for height, the furthest left is used.

This also applies to other ammunition.

In an answer* to a related question, it is stated that:

[A meteor] may not intersect with a Player, an NPC or a Chest.

If your house is only large enough for your NPCs, it's quite likely you're already safe. If not, as an alternative to making a skybridge barrier, you might instead make an "attic" full of chests. This will cause the game to look for a different location entirely rather than leave only a thin layer of meteorite, as a skybridge would.

**My understanding is that the rules listed in the linked post were determined by examining the game's code, but it wasn't done by me, so caveat emptor. ;-)*