Originally posted by Zep Tepi:

You get 100% of your materials back so you won't have to chop trees all over again. The wood and whatever else you have will be on the ground waiting for you to pick it up again. So, yeah, rebuild after you run out the timer. It take a few days for items on the ground to despawn, and they never despawn when in range of a workbench. You lost time, but not materials.

I'm fairly sure you don't get the core wood from staked walls back. But since they are a dedicated defense structure I guess if you can afford to build too many of those you will want and are able to fight the enemies at least partly too.