It's solved by paying attention to how many people need new houses and not building too many at once ;)

Seriously though, it's something the guys from BlackLiquid Team had a look at, and there's apparently no way to add a "Work" button to open/close houses with the modkit. They tried fiddling with the upgrade option to do it too, and it just wasn't working well.

So yeah. Not building too many houses at once, keeping an eye on the families / houses statistics in the TownHall and keeping in mind that the families number can be biased as a widowed elder + a young adult seem to be counted as 1 potential family in the stats when in reality they'll never move in together.
I try to keep my number of available houses around 3/4th of the number of potential families and regularly have a look around town to see if I have a lot of houses with single elders which will get freed soon, or if I have a majority of houses full of adult kids that desperately need a new place.

i thought it was pretty silly the first time i realized i could build too many houses too quickly, seperating couples so much that the town dies from lack of repopulation >< Gotta take game difficulty where i can get it though (since i never seem to get disasters, do those only trigger at high populations?)

Disasters are totall random. Current town in year 28 hasn't seen anything wrong, but the previous one had a tornado, disease oubreak and a fire before year 10.

I think my "record" was a Tornado in the very first autumn, a fire the next spring, a fire in year 3, another tornado in year 6, and a final tornado right in the middle of town in year 10. Dunno why the guys in that town had been Banished, but apparently they had very very bad karma!

ive never had a disaster exept fire and pests in crops, both very easily fixed so i dont count them.