Sounds just like what the game would do. 
What version are you using? You might want to upload your save file in the following thread so the devs might take a look into it.
http://discourse.stonehearth.net/t/epic-gigantic-a14-a15-saves/19524/60
Nice building though. I build a castle with 303 stone once, which even finished. It took the hearthlings more than 3 months though, because only about 1-3 of 24 hearthlings would work on it, while the others idled.