Well this just happened today, I started my third hut and it was maybe at 25% or somewhere around there. The other building is finished and the event box for that already showed up. So I closed the like box that opens when you start playin 'cauz I had to take a shower, I come back and and an event box shows up saying you have completed building a new hut. Your tribe can now hold a bigger population. Everything is normal except when I look at the hut it's only at 34%. Then all the people are celebrating around the old hut? Is this a glitch? Oh and I can't hold a bigger population..too bad... (Max is still 17)

This is a small bug that has been talked about here before. It's just a message error and doesn't affect the actual work on the huts.

Yes, this is just a little glitch! and there are other threads about it.
It doesn't matter at all! this little windows pops up in totally disorder!! It doesn't have any effect to your game.

Yeah,don't worry. I had that happen to. Just put the builder back to work and they'll keep building the hut till it's finshed.

Yay! they finished the hut and now my pop is 19 woo hoo!!