As you’re examining your basement, be sure to look for evidence of homewreckers like termites and carpenter ants. Termites leave telltale tunnels when they travel over nonwood surfaces. Carpenter ants leave little piles of sawdust under their exit and entry holes. Both pests will hollow out boards right up to the surface, so that what looks like a solid board is actually just a shell. I’ve done demolition work in which I’ve grabbed a 2×4 to give it a whack, and it crumbled in my hand. Nothing inside but a bit of dust and maybe a critter or two.
If you have the faintest suspicion that your basement might harbour either of these villains, call a professional pest expert.